Animal breeding course

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Lecturer: Abdirahman Awsamire (MSc.) Faculty of Animal Science 1

UNIERSITY OF HARGEISA

COLLEGE OF AGRICULTURE, VETERINARY AND ANIMAL SCEINCE

Faculty of Animal science

Program Faculty Animal Science

Courses Title Animal breeding

Pre-requisites Animal genetics

Instructor Abdirahman Awsamire (MSc.)

Course

Description

The scope of this course includes Historical development and modern concepts of

animal breeding. Breeds of livestock and major traits in farm animals; Genetic

parameters: heritability, repeatability, and correlation among traits. Categories of

relationships; Principles and methods of selection (Selection based on records of

individuals, progeny, pedigree, collateral relatives and combination of records

simple selection indices). Mating systems in farm animals; Recording and

standardization of herd records; Breeding programs in the tropics and their results;

Development of new breeds; Principle of nucleus breeding program; Conservation

of farm animal genetic resources:

Course

objective

At the end of the course, the student will be able to:

Describe the historical development and modern concept of animal breeding

Identify and characterize the different breeds of livestock breeds

Understand how to estimate genetic parameters

Describe the categories of relationship and evaluate coefficients of

relationship and inbreeding



Understand the principles of nucleus breeding program

Identify methods of animal genetic conservation

Understand the principles, types and methods of selection

Describe the nature, opportunities and threats of animal breeding in the

tropics



ANIMAL BEERING COURSE

1. INTRODUCTION Animal breeding is the application of principle of Genetics and Physiology of Reproduction for

improvement of the animals. Improvement is betterment of the characters both qualitative and

quantitative over those of the ancestors, over that of the average of family.

Animal breed: breed is group of livestock (animals) with in the species of common origin. They

have certain distinguishing characters not found in members of other group in the same species.

These characters are transmitted to successive generation.

Breeder: Breeder is one who planned and determined the type of mating. For practical purpose

breeder of an animal is a person who owned the dam of that animal at the time of breeding (horse

race course term).

Task of animal breeder: The task of animal breeder is to speed up and control every process of

improvement. A progressive breeder should bring about new combination of genes which are best

suited to his purpose than the existing combinations. Hence he has to learn.

1. Probable genetic make up of his animals through

a. Animals individualities

b. Parentage

c. Performance of their close relatives

2. Combining the favourable characters by

a) Selection

b) Breeding

History of Animal Breeding

Exact date as to when animal breeding was practised is not available from history. The evidences

gathered from the archaeological excavations indicate that the Mediterranean countries (Egypt,

Rome Greece) initiated the animal breeding. Egypt and Arabs are known for the horse breeding.

Arabs in 12th

century considered that dam was important in breeding and not aware of importance of

the sire. At about the same time in Denmark and Holland the cattle breeding was practised by

providing better environment such as feed. In U.K; the royal families in 14th

century considered

performance of horses for selection and breeding. The Earls and Dukes took interest in cattle

breeding and imported the cattle from Denmark and Holland. Until the 18th

century there was no

planned or systematic animal breeding. During industrial revolution in England (1760) the people

started migration from villages to cities. This created a heavy demanded for milk and meat. Robert



Bake well (1725-1790) an English man is generally acknowledged as great pioneer in Animal

Breeding and father of Animal Breeding.

Bake wells contributions and methods:

1. He had definite ideas, such as beef cattle should be low set, blocky, and quick maturing.

2. He gave more importance to sires by selecting best animals.

3. He started a systematic progeny testing of sires. He lent the good sires to other breeders for

given fee and also insisted that the progeny of the sire should be rared under similar conditions. He

used those males which gave the best progeny in his farm.

4. While breeding best to best he practised inbreeding which led to development of true breeding

stock.

5. He also kept the records of individuals.

In 18th

century pure breeding was preferred and people wanted information on pure bred animals. To

supply authenticated information one Mr. George Coat in 1822 opened the Herd Book for Short

Horn cattle. It was followed by opening of Herd books for most of the breeds by middle of 19th

century. The first association of farmers for milk recording was formed in Denmark and followed by

all other milk producing countries.

Modern History of Animal Breeding

BREEDING ANIMALS

AGRISCIENCE AND TECHNOLOGY

TERMS USED IN BREEDING ANIMALS

BREED: Breed is made up of animals of the same species that share common traits.

BLOODLINES: Bloodlines are groups within breeds; tend to have one common

ancestor.

PUREBRED: Animals registered in a breed or eligible for registry.

INHERIT TRAITS OF ANIMALS

COLOR

MILK CAPACITY

HORNS

SIZE

TYPE



OFFSPRING THAT HAVE TRAITS GENETICALLY DIFFERENT FROM THEIR PARENTS ARE

KNOWN AS MUTANTS.

BREEDS OF CATTLE

ANGUS: Originated in Scotland. Black, polled and have a smooth coat of hair.

BRAHMAN: Originated in United States. Light gray to nearly black, loose skin and

large humps over the shoulder; tolerant of heat and insects.

BRANGUS: Developed by crossing Brahman and Angus cattle. Solid black and polled.

CATTLE BREEDS CONT.

CHAROLAIS: Originated in France. White to a light straw color; large breed, most are

naturally horned.

CHIANINA: Originated in Italy. White except for the switch of the tail, which is

black; skin has a black pigment. Largest beef breed.

HEREFORD: Originated in England. White face and red bodies. A horned breed.

CATTLE BREEDS CONT.

POLLED HEREFORD: Developed in the United States. White face and red bodies;

polled.

LIMOUSIN: Originated in France. Most are red but may be light yellow or black.

They usually have horns.

SANTA GERTRUDIS: Developed by the King Ranch in Texas. Cherry red, usually

horned and have loose hide. Crosses of the Shorthorn and Brahman breeds.

BEEF BREEDS CONT.

SHORTHORN: Originated in England. Red and white, with a red-white mix (roan),

have horns except for the Polled Shorthorn breed.

SIMMENTAL: Originated in Switzerland. Faces are white/light straw and their

bodies are red to dark red.



DAIRY CATTLE BREEDS

AYRSHIRE: Originated in Scotland. Red, mahogany, brown or white in color.

Rank third in milk production (11,700 lbs. per year with 4.0 % milk fat).

BROWN SWISS: Originated in Switzerland. May be any shade of fawn with white

markings. Rank fourth in milk production (10,600 lbs. per year with 5% milk fat).

DAIRY BREEDS CONT.

GUERNSEY: Originated off the coast of France. May be any shade of fawn with

white markings; horns turn outward and toward the front. Tied for fourth in milk

production (10,600 lbs. per year with 5% milk fat).

HOLSTEIN: Originated in the Netherlands. Black and white color patterns. Rank

first in milk production (14,500 lbs. per year with 3.5% milk fat).

DAIRY BREEDS CONT.

JERSEY: Originated on the Isle of Jersey. Color range from cream to almost black.

Ranks fifth in milk production (10,000 lbs. per year with 5.4% milk fat). Smallest of

the dairy breeds.

SWINE BREEDS

AMERICAN LANDRACE: White breed with ears drooped over the eyes. Produce

large litters of pigs.

BERKSHIRE: Black with six white points: each foot, some white on the face and a

white tail switch; erect ears.

CHESTER WHITE: White breed; popular in the northern parts of the United States.

=



SHEEP BREEDS

FINE WOOL SHEEP - Rambouillet, American Merino, Delaine Merino and Debouillet.

MEDIUM WOOL SHEEP - Cheviot, Dorset, Finnish Landrace, Hampshire, Shropshire,

Southdown and Suffolk.

LONG WOOL SHEEP - Cotswold, Leicester, Lincoln and Romney.

SHEEP BREEDS CONT.

CROSSBRED WOOL SHEEP - Columbia, Panama and South dale.

GOAT BREEDS

MOHAIR AND CASHMERE - Angora; most of these are grown in Texas and other

southwestern states.

DAIRY GOATS - LaMancha, Nubian, Saanen and Toggenburg.

POULTRY

Poultry includes chickens, duck and turkey. Other poultry animals include quail,

guinea, ostrich and emu.

Most common breeds of chickens are White Leghorn, White Rock, Rhode Island Red,

Barred Rock and New Hampshire.

Chickens are selected for one of two uses: eggs and meat.

AQUACULTURE

Term used to describe the farming of fish.

Examples include: catfish, trout, tilapia, hybrid striped bass, shrimp, oyster, crawfish,

red fish, snails, crabs, alligators and frogs.



KINDS OF BREEDING SYSTEMS

STRAIGHTBREEDING: Mating of animals of the same breed.

Different approaches of straight breeding include purebred breeding (mating purebred

animals), outcrossing (mating animals of the same breed but of different families in

the breed) and inbreeding (mating animals of the same breed with closely related

animals).

BREEDING SYSTEMS CONT.

CROSSBREEDING: Involves mating animals of different breeds.

Used to improve the quality of the products yielded by the offspring.

Used to produce calves with more meat, no horns or to accomplish other specific

genetic purpose.

PUREBRED PRODUCTION SYSTEM

Used to produce purebred animals that will be used for meat, milk or other purposes.

May compete in shows.

Raise both male and female animals.

Must keep accurate records.

MEAT-ANIMAL PRODUCTION SYSTEM

COW-CALF PRODUCTION - Involves keeping cows to produce calves that are

used for meat.

Calves are weaned at about 500 lbs.



METHODS OF INSEMINATING LIVESTOCK

NATURAL INSEMINATINATION - Involves using animals to mate in pastures or

pen breeding.

ARTIFICIAL INSEMINATION - Involves collecting semen from a male and

depositing it in the reproductive tract of the female.

ADVANTAGES OF USING AI

AI allows the use of semen from superior males that are owned by another party.

AI makes it possible for a male to breed many more females than could be done

naturally.

* Semen can be stored for a week at 41F or for several months frozen at -320F (liquid

nitrogen).

IMPORTANT INFORMATION IN BREEDING ANIMALS

SPECIES AGE/BREED GESTATION

COW 14 MONTHS 283 DAYS

SOW 12 MONTHS 114 DAYS

EWE 17 MONTHS 148 DAYS

DOE 18 MONTHS 151 DAYS

MARE 2-3 YEARS 336 DAYS



ESTRUS SYNCHRONIZATION

Involves using hormones to get several females to come in heat at the same time.

Used when using advanced breeding procedures such as superovulation (getting the

female to produce a number of eggs at one time) and embryo transfer.

PREGNANCY TESTING

BLOOD TEST

URINE TEST

RECTAL PALPATION (MOST COMMON METHOD USED)

“BUMPING”

SIGNS OF PREGNANT FEMALES GOING INTO LABOR

ENLARGED UDDER

SWELLING OF THE VULVA

HOLLOWNESS IN FRONT OF THE PIN BONES

NERVOUSNESS

GOING AWAY FROM THE HERD

GIVING BIRTH

Most animals give birth without assistance.

Calves should be born within one hour after labor begins.

Calves are normally delivered with the head between the two front legs.

Cow may need assistance if calf is in a different position.

AFTER THE BIRTH

It is very important that the calf gets the first milk known as “colostrum”.

Colostrum is high in antibodies and other substances that help the new animal survive.



Animal should expel the placenta 3-6 hours after giving birth.

1.1. Breeding of Dairy Cattle

1.1.1. Selection Methods of Dairy Animals

This selection is based on information available on the ancestors like

parents, grandparents and great grandparents. The contribution beyond

three generations is not much to be considered in pedigree selection.

Pedigree selection enabled selection at an early age, and selection of

males which do not express the traits like milk production through they

transmit the genes for the traits.

Individual Selection:

Selection is based on the individuals own milk vein, teats, pelvic cavity

and udder. This is ideal for characters with high heritability. Where as in

dairy cattle most of the economic traits have low to moderate

heritability.

Family Selection:

Where families are selected or rejected as units according to the

phenotypic value of the family. The families may be full sibs or half

sibs.~ The method is useful when the character for which selection is

made has‟ low heritability. Two modifications of family selection

applicable to dairy; cattle are sib selection and progeny testing.



Sib Selection:

This is a type of a selection where in the selected individuals do not

contribute to the family means. This applies to selection of males which

do not express the characters and selection of females at an early age.

Progeny Testing

The criteria of selection is the mean value of an individual‟s progeny,

which comes close to the breeding value. The value of an individual is

judged by the mean value of its progeny known as breeding value. It is

equal to the sum of average effects of genes;, the individual carries.‟

Progeny testing prolongs the generation interval. As the bull had to wait

its progeny test result before „its use, but it is more than made up by the

increase in accuracy of selection. A higher intensity of selection is also

possible by employing Artificial insemination with pedigree semen.

Culling of Dairy Animals:

Culling is elimination or weeding out of undesirable animals from the

herd for reasons of uneconomic, poor production, or very poor

reproductive ability, with sterility problems and breeding, irregularities,

very poor conditions, stunted growth, suffering from incurable illness, or

disease animals found to be positive for serious infectious diseases like

Tuberculosis, Johns disease, Brucellosis, lost one or more quarters and

teats of the under due to chronic mastitis resulting in marked reduction

in milk production. Undesirable breed characters present in young

animals.

When the herd is a pure bred herd leading to disqualifications family

lines, exhibiting heritable characters like supernumerary teats, loose

horns in cows of certain breeds. Disable animals due to injury or loss of



organ, extreme lameness leading to unmaintainable conditions, unhealed

fractured animals etc., come under the animal proposed or culling. The

culled animals carry lower values and a separate list is made for such

called animals and it is known as culling list.

When the culling cows for poor production, the entire lactation yield is

considered and preferably first two lactations are observed and if the

lactional yield is less than what is expected from the breed or herd, the

animal is included in the culling list.Very old animals are culled, as their

maintainance will be uneconomical. Male animals or other animals

surplus in the farm or not useful in the farm and they are culled. Calves

born much below the normal birth weight are included in the culling.

Yearlings animals male or females, stunted much below their normal

body weight, bad confirmation are culled.

Valuation and culling is done on the farms every year at least once in

year. In some farms culling is done twice a year however doing it once a

year is must.



1.1.2. System of Breeding

Breeding is defined as the crossing of the male and the female parents to

get the off spring for the characters desired. The main breeding methods

are

1) In breeding 2) Out Breeding

Inbreeding:

Inbreeding is the mating of closely related individuals, whose

relationship is more than the average relationship of the population. The

example is the individual having one or more common ancestors or

relatives. The measures of inbreeding is the coefficient of inbreeding. In

breeding may be mild, or close inbreeding and line breeding.

Close Inbreeding:

In this type is inbreeding mating is made between very closely related

individuals such as full brothers are crossed with full sisters, or

offspring‟s are crossed with parents.

Advantage of Inbreeding:

i. Undesirable recessive genes may be discovered and eliminated by

further testing in this line.

ii. The progeny are more uniform than and breed progeny. It

increases homozygosis and decreases genetic variance.

iii. Breaking down of population into different inbreed lines.



Disadvantages:

i. The progeny becomes more susceptible to diseases.

ii. Breeding problems and reproductive failure usually increases.

iii. It is difficult to find out the stereo breeding at which it should be

discontinued, in order to avoid the bad effects of the system.

iv. It depresses‟ vitality in early life than in later life.

v. A small breeder stands a good chance of gain by doing too much in

breeding. A rule to follow is never to inbreed more than 12 % and

then only in exceptional cases.

vi. In breeding appears to have little value in dairy cattle breeding

programs, because of its numerous detrimental effects.

Line Breeding:

It is repeated back crossing to one outstanding ancestor, so that its

contribution to the progeny is more. In this type of breeding mating are

made to concentrate, the inheritance of desired characters of some

favored individuals.

i. It brings about the uniformity of the required type.

ii. The dangers involves in case in breeding can be reduced.

The breeder will select the animal for its pedigree giving due

consideration for the individual merit. This may result in very little

benefit in new generation, in some case having the benefit.



Outbreeding:

It is the opposite of inbreeding. Mating unrelated animals is known as

out breeding. It is divided into six classes as detailed below;

1. Pure breeding

2. Line Crossing (Crossing of inbreed lines)

3. Out Crossing

4. Cross Breeding

5. Grading up

6. Species Hybridization

Pure Breeding:

It is mating of male and female belonging to the same breed. Pure

breeding is a sort of out breeding. The examples of pure breeding are

Jersey Cow -x Jersey Bull

The outstanding advantage of pure breeding is for production of bulls for

breeding purpose only pure breeding is to be followed in almost all the

breeds except in case of inter-se-mating. It avoids mating of closely

related individuals.

Cross Breeding:

It is mating of animals of different breeds. Cross breeding is followed

for breeding animals for milk production and meat production. Zebu

breeds of cows and nondescript cows are crossed with exotic breeds like

Holstein Fresian, Brown Swiss and Jersey bulls or their semen, to

enhance the milk production potential of the progeny.



Advantage:

1. The desirable characters of the exotic parent are transmitted to the

progeny which the indigenous parent does not have.

2. In India Cross-breeding and cows is done by using the exotic bulls

and the progeny inherit the desirable characters of the parent like

high milk yield early maturity, higher birth weight of calves, better

growth rates, better reproductive efficiency and indigenous parents

characters like, heat tolerance, disease ability to resistance

3. In pairs the way to evolve new breeds with desirable characters.

4. Hybrid vigor is made use. Of in the progeny

5. Results are seen more quickly in characters like milk yield in the

cross bred progeny.

Disadvantages:

1. The breeding merit of cross breed animals may be slightly reduced.

2. Cross breeding requires maintenance of two or more pure breeds in

order to product the cross breeds.

• Dairy Cattle Production and Management Part



Chapter 3: Breeding Programs

The aim of animal breeding is to genetically improve populations of livestock so

that they produce more efficiently under the expected future production

circumstances. Genetic improvement is achieved by selecting the best individuals

of the current generation and using them as parents of the next generation. To

select the best animals one needs to define explicitly what is meant with "best".

This means that it is necessary to specify the direction in which we want to change

the population. Defining the breeding goal is the first step when designing a

breeding program. It is useless to design a breeding program if there is no idea of

the desired genetic change.

NB. A breeding program is the organized structure that is put into place to

genetically improve livestock populations.

Successful genetic improvement requires breeding programs to have (at least)

the following components:

A system to record data on selection candidates. Without data on selection

candidates it is impossible to identify the best individuals.

Methods and tools to estimate the genetic merit (breeding value) of selection

candidates. This step is called the "breeding value estimation".

A system to select the animals that become parents of the next generation, and

mate them to produce the next generation.

A structure to disseminate the genetic improvement of the breeding program

into the production population. In most cases, the breeding population and the

production population are (partly) separated. Since the aim is to improve

livestock production, genetic improvement created in the breeding population

should be disseminated into the production population.



6.1. The breeding goal

The breeding goal, or breeding objective, is the starting point of animal breeding.

Broadly speaking, the breeding goal is the direction in which we want to improve

the population. The choice of the breeding goal affects the structure of breeding

programs. Broiler (chicken for meat) breeding programs for example differ from

layer (chicken for egg production) breeding programs because improvement of egg

production requires another breeding program than improvement of meat

production.

The breeding goal has a number of characteristics.

1. The breeding goal is a combination of traits. It specifies the relative

importance of each trait. In principle, all traits of importance should be included in

the breeding goal. Thus the breeding goal only depends on the importance of a

trait, not on its genetic parameters. An important trait of low heritability should be

included in the breeding goal, whereas unimportant traits should be left out,

irrespective of their heritability.

2. The breeding goal should aim at the future. Animal breeding is a long-term

activity. It takes a long time before genetic improvement due to selection is

expressed in the production population.

3. From an operational point of view, the breeding goal should ideally

summarize all traits in a single criterion. A single criterion to express the

quality of selection candidates is convenient because animal breeders can

simply rank their selection candidates on this value and select the highest-

ranking individuals. A breeding goal expressed as a single value can be

obtained by weighting all traits by an (economic) factor, so that the breeding

goal is a sum of breeding values weighted by their (economic) value.



Questions should be raised in developing breeding programs are like:

what market the breeding goal is aimed at;

whether the breeding goal should be based on the competitive position of the

breeding company or on an economic model of the production herds

Existence of political or market circumstances such as production quota that

affect the breeding goal.

In Western countries, breeding goals primarily include economically important

traits such as milk yield, meat production and egg production. In addition, breeds

are often specialized for a single purpose; dairy breeds are kept for milk

production and beef breeds for meat production, layers for egg production, broilers

for meat production. In developing countries however, the situation is quite

different, because livestock is often kept for auto-consumption and not to produce

for a particular market.

==========================Message==========================

NB. The breeding goal specifies which traits should to be improved, in which

direction and the relative emphasis given to each trait.

=============================================================

In animal breeding, there are two common approaches to define breeding goals.

The first approach is to express breeding goals as a weighted sum of economic

values and breeding values. In this approach, economic weighting factors of traits

(economic values) are based on an economic model of the production system. The

second approach is to express the breeding goal as a set of desired gains for each

trait. The desired genetic gain for each trait is based on marketing and commercial

considerations of breeding companies. In many cases, desired gains are based on

maximizing the market share of the breeding company in the time frame.

Breeding goals based on economic models of the production system:



When breeding goals are based on an economic model of the production system,

the economic value for each trait is determined by modeling the effect of that trait

on the profit of a production herd.

NB. Breeding goals can be expressed in terms of economic values, which

express the increase in profit due to a single unit improvement of a trait, or as

desired genetic gains.

6.3. Design and evaluation of breeding programs

Design of breeding programs: The structure of breeding programs depends on

both the species and the breeding goal. The optimum design of a breeding program

will differ between species with large reproductive capacity and species with small

reproductive capacity, between breeding programs that aim to improve production

or reproduction traits, and low heritable traits versus high heritable traits. The

question whether the breeding goal traits have high or low heritability is

important. In the case of high heritability, (pure line) selection is an adequate tool

to genetically improve the population. When breeding goal traits have low

heritability, it will be more difficult to improve them by means of selection, and

crossbreeding may be a solution.

For traits where selection is the best option, the next question is whether breeding

goal traits are favorably correlated. If breeding goal traits show a strong but

unfavorable correlation, then it will be difficult to improve them within a single

population. In that case, the development of separate sire and dam lines may be a

solution. When separate sire and dam lines are the best option, then the final step is

to choose or develop separate lines and to optimize selection within those lines. On

the other hand, if breeding goal traits are favorably correlated then they can be

improved within a single breeding population by means of index selection.

The final step is then to optimize the breeding scheme, which involves questions

related to the size of the population and the data recording strategy.



Judging the quality of breeding programs

Choosing the best breeding scheme among a number of alternatives requires

yardsticks to measure the quality of breeding schemes. Such yardsticks can be

developed only when there is a well-defined breeding goal.

Given that the breeding goal is clearly defined, there are three criteria that

summarize the quality of a breeding program.

These are:

1. Selection response for the breeding goal.

2. Maintenance of genetic diversity as measured by the rate of inbreeding.

3. Costs of the breeding program.

1. Selection response for the breeding goal traits is the revenue of a breeding

program, whereas loss of genetic diversity and financial costs are the expenses of

a breeding program. Selection response, loss of genetic diversity and financial

costs are expressed in different units. The problem therefore is to combine them

into a single criterion for the quality of a breeding program.

A comparison of breeding schemes based on selection response and the rate of

inbreeding can be done as follows. To avoid long-term loss of genetic diversity an

upper limit can be set to the rate of inbreeding.

Next, alternative breeding schemes can be judged by comparing their selection

response at the same rate of inbreeding. The scheme with the highest selection

response at the same rate of inbreeding (e.g. 1%/generation) is the best scheme.



Evaluation of breeding programs:

Once a breeding program is operational it is essential to routinely evaluate the

results. Evaluation may consist of comparing realized genetic improvement and

rates of inbreeding with values expected when designing the breeding program.

When there are clear differences between expected and realized selection response

and inbreeding, then one needs to find the causes of those discrepancies and if

possible improve the breeding program.

Reasons that breeding programs do not yield the expected genetic improvement

are:

a) the use of inappropriate models for breeding value estimation, for example

when the models do not include systematic environmental effects that are

present in the data;

b) overestimation of the genetic parameters (e.g. h2) resulting in biased EBVs

and overprediction of the expected response;

c) preferential treatment among selection candidates resulting in selection of

individuals that received good treatment" instead of genetically superior

individuals, and

d) unexpected correlated response in other traits.

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The quality of alternative breeding schemes can be judged by comparing

selection response, rate of inbreeding and costs of the alternatives.

2. BREEDS OF LIVESTOCK AND THEIR MAJOR TRAITS

General characteristics of Somalia Livestock

A. Diversity in livestock types:

Ethiopia has a diversified topographic and climatic condition. Within this

diversity, various livestock breeds or types have evolved; however, there



are no detailed studies on the identity of each type and their genetic

potentials.

Classification of Ethiopian Livestock:

I) Cattle: generally classified in to four main groups

1. Humpless: Brachyceros sheko (mitzan, Goda) Bench Zone: Hamitic long

horn-Kuri (Kouri)

2. Zebu cattle: Arsi, Borana, Barca, Jijiga small zebu,

Harar short horned, Jem Jem black, Bale highland zebu and various small

short horned types.

3. Sanga: Abigar, Danakil (Afar, Adal, Raya-Keriyu), Raya-Azebo(Oromo-

Azebo)

4. Intermediate sanga-Zebu cattle: Arado, Fogera, Horro and Jiddu.

General characteristics of Zebu cattle:

Hump: Differ in size depending on breed, age, sex, fatness.Function of

hump is not well known in all the breeds. Body: Body is usually narrow

with sloping rump. Legs: are usually long to keep the distance between the

body and ground more so as to avoid heat of the ground. Heat tolerance:

Because of low basal metabolic rate, low growth rate, less yield they

generate less of internal heat. They have more capacity to dissipate heat by

conduction and evaporation. They have short sleek coat, high surface area

to body mass ratio and high number of sweat glands. Tick resistance: They

are partially resistant to ticks and they have the ability to repel the flies by

movement of their skin. Nutritional requirement: They have low nutritional

requirement because of small size, low basal metabolic rate. They are

highly efficient in digestion of low level of feeding (low quality feed).

When there is shortage of feed and bad living condition smaller animals are

superior to larger animals. Productivity: Late maturity, longer inter calving



period, shorter lactation length, poor yield and failure let down milk with

out calf. However milk contains higher percentage of fat and solid-not-fat.



II) Sheep: Ethiopian sheep types are classified into 3 main groups,

based on hair type and tail or rump type.

Classification Breed Geographic distribution

Hairy thin

tailed

Bonga, Horro Kefa, Wollega

Fat tailed Menz, Arsi Bale,

Tukur

North-Shewa, Arsi and Bale, Wello

Fat rumped Black head Somali,

Adal

Hararghie, Somali, Afar Sidamo, Bale,

Wello, Shewa

III) Goats:

Using various characteristics such as size, color, horn etc. the following

classification is done.

Breed Geographic distribution

Oromo – Sidamo Southern Shewa and Northern Sidamo

Arsi – Bale (Gishe) Highlands of Bale and Harargie

Somalli Ogaden, Mudugh,

Borana

Ogaden and Elkere (Somali)

Adal (Afar, Danakil) North rift valley in wello and Afar

Bati South west wello, Western Ethiopia

Dinka Southern Ethiopia

Southern Abyssinian Wello Mule



IV) Camel: There is no classification work, but they are one humped

(Dromedaries)

V) Horse: Classified in to two, 1. Oromo Horse, 2. Dongola

VI) Donkey: classified into four: Jima donkey, Abyssinian donkey,

Ogaden donkey and Sennar donkey

VII) Mule: Two groups: Sennar mule and Wello Mule

VIII) Chicken: No detailed classification work

Livestock in Ethiopia are generally poor for most of the economic traits

e.g. Milk, meat, power Production egg etc. Livestock do have multi-

purpose use

Cattle - Draft power, milk, meat, hide, manure

Sheep – Hair, meat, skin and milk in some area

Goat – Meat, milk, skin,

Horse – Draft power (ploughing and pack) and transport

Donkey – Draft power as pack and transport

Mule - Draft power as pack and transport

Camel – For milk, meat and pack and transport

Poultry – Egg and meat



Ethiopian cattle

Group Zebu Sanga Intermediate

Example –

Breed

Related types

BORAN

Somali Boran, Tana

land Boran, Kenya

Boran

DANAKIL

Adal

Cattle of Jibuti

ARADO

Tigre, Wellega,

Borica

Bileri

Origin habitat

Borana

(province of Ethiopia)

Ethiopia (South east)

(long horned sanga)

Low land and semidesert of

Eritrea.

Rared by Afar and Danakil

tribes.

North –east Amhara

of Ethiopia.

Functional traits

Birth wt

Weaning wt

Mature wt

25 kg.M : 23 kg F

170 kg

318 –680 kg. M. 250-

450 kg F

-- --

-- --

250-375 kg.M 200-300 kg.F

----

-----

----

Dressing % 54-75% V. high -- --- ------

Milk yield

Fat

L.L

454-1814 kg

4.1-6.8%

139-303 days

200-300 kg

6.8%

160-225 d.

---

---

----



The following points of comparison bring out the chief differences between

Bos taurus and B. indicus cattle:

European (B. Taurus)

cattle

Zebu (B. indicus) cattle

1. No hump 1. Hump present in thoracic or cervico-thoracic

region.

2 . Rounded ears, held at right

angle to the head.

Long drooping ears, pointed rather than

rounded

3. Head short and wide. Long and comparatively narrow head.

4. Skin held tightly to body.

Dewlap, umbilical fold and

brisket small.

Skin very lose, often falling away from body

in folds

Dewlap, umbilical fold and brisket

extensively developed.

5. Skin relatively thick, (7-8mm) Skin relatively thin, average thickness 5-6

mm.

6. Large amount of

subcutaneous fat especially in

mature animals.

Relatively small amounts of subcutaneous fat

at all stages.

7. Back line straight or relatively

straight. Back line high at shoulders, low behind

hump, high over pin bones, sloping down

markedly over tailbud

8. Hip bones wide and

outstanding

Hip bones narrow and angular.



Certain of the above differences have probably been reduced as a results of

artificial selection, particularly animal breeding by man, since the species

was domesticated. Thus, items 7, 10, 16 and 19 have probably been

modified, to a greater or lesser extent, by man. Certain of the features noted

are of little or no significance with respect to productive performance or the

adaptation of the species to its environment. However, the majority of the

factors listed are of great importance in one or other of these respects.

3. VARIATIONS AND ESTIMATION OF GENETIC PARAMETERS

Genetic and Environmental variation

The variation is raw material on which a breeder works to produce

genetically superior animal. The variation noticed in any matric

(quantitative) trait arise from two sources

Genetic variation: Variation because of particular combination of genes.

The genetic variation noticed among animals is transmitted to next

generation and any improvement made is permanent important. The genetic

variation is caused by Number of loci involved. Exact number of gene loci

involved for any quantitative trait is not known. Even if you take one locus

possible type of gametes and genotype of progeny is enormous. The

recombination of genes due to crossing over leads to several types of

gametes. e.g.(with one locus)



5.1. Current Situation of Somalia Animal Genetic Resources (AnGR)

Somalia Farm Animal Genetic Resources are mostly underutilized biological

resources

Farm Animal Genetic Resources of Somalia:

In Ethiopia, classification of farm AnGRs into breeds is far from complete.

Classification studies have been conducted on most of the cattle and goat breeds

that exist in the country. However, research is at its rudimentary stage for the other

species, particularly chickens. Therefore, the list of breeds presented below should

be viewed from this perspective. The most common farm animals of the country

can be categorized into mammalian, avian and honeybee species. Cattle, sheep,

goats, camels, donkeys, horses and mules are the major farm animals that lie under

the mammalian category

Populations Types/ subtypes

/breeds?

44.32 million Cattle---------------25 types or sub-types

23.62 million Sheep------------------13 types or sub-types

23.32 million Goats-----------------15 types or sub-types

6.06 million equines------------------- (4donkey, 2horse, 2mule)

2.31 million Camels---------------------4 types or sub-types

42 million chickens--------------------------5 types or sub-types



Cattle breeds

Indigenous breeds: major cattle breeds identified so far are Arsi, Begayit,

Ogaden, Borena, Goffa, Arado, Nuer, Gurage, Jidu, Karayu/Afar, Harar, Horro,

Smada, Fogera, Mursi, Raya-Azebo, Adwa, Jem-Jem, Sheko, Ambo, Jijiga,

Bale,Hammer, Medenece and Abergelle.

Medenece and Abergelle are recently reported by the Tigray Regional Bureau of

Agriculture and Natural Resources Development to exist in that part of the country.

Since there has not been any exhaustive identification and characterization work, it

is possible that new breeds are to be described yet. Out of 25 indigenous cattle

breeds, the Borena, Horro, Fogera, Karayu, Arsi and

Nuer are the widely used breeds.

Sheep breeds

Indigenous sheep breeds: Fourteen Ethiopian sheep populations are traditionally

recognized as sheep breeds. Microsatellite DNA-based analysis revealed that some

breeds could not be separated at the genetic level, resulting in six genetically

distinct breed groups. In Table 5.1 breeds and breed groups are listed.



Table 5.1. Traditional breeds, breed groups, ecology of Ethiopian/somalia sheep

Exotic sheep breeds: Exotic sheep breeds introduced for their wool and mutton

production are Awassi, Hampshire, Blue-de-main, Merino, Romney, Corriedale

and Dorper. Crossbreeding of the Menz breed with the five exotic breeds, namely:

Awassi, Hampshire, Bleu-de-Main, Romney and Dorper are being used for

development and research activities.

Goat breeds

Indigenous goat breeds: Major goat breeds existing in the country are Begayit,

Ille, Afar, Hararghe Highland, Arsi-Bale, Short-eared Somali, Woyito-Guji, Long-

eared Somali, Central Highland, Abergelle, Western Highland, Widar, Western

Lowlands, Maefur and Keffa. Moreover, Felata, Arab, Gumuz, Agew and have

been recently reported.

Equine breeds

Donkey breeds that exist in the country are the Jimma, Abyssinian, Ogaden and

Sinnar. Major breeds of horses that have so far been well recognized are the

Oromo and Dongola. In Ethiopia, crossing of Asses with mares to produce mules

dates back to centuries. Except for two well known, namely: Sinnar and Wollo

Mule breeds, there are no other well-defined hybrids in the country.



In Mekele University,Tigray region, phenotypic characterization of local donkeys

has been carried out. However, such activities have to be complemented with

proper genetic characterization in order to classify the donkey types found in the

region or elsewhere.

Camel breeds

Attempt to classify Ethiopian camels has not been satisfactory so far. Wilson

(1984) has classified and described major camel breeds in the country as the Afar,

Borena, Anfi and Somali/Ogaden breeds.

Poultry breeds

Indigenous chicken breeds: Based on geographical locations, indigenous chicken

breeds identified so far are Horro, Jarso, Tililli, Tepi and Cheffe breeds that are

found in the central highland areas. The naked-neck breed found in northern,

northwestern, western and southern lowland areas of the country.

Exotic chicken breeds: Several layer, broiler and dual-purpose exotic chicken

breeds introduced into the country are being used for food and agriculture. Rhode

Island Red (RIR), White Leghorn, Lawman Brown, Cobb-500, Fayoumi, Bovans

Brown, Arob Acre and Bubcocks are reared by small and large-scale commercial

producers in urban and peri-urban areas. Besides, RIR and White Leghorns as well

as their crosses with indigenous chicken are used by rural smallholders for egg and

meat production.

Honeybees

It is estimated that Ethiopia has about 10 million honeybee colonies. Species of

honeybees identified so far are Apis melifera adansol, Apis melifera lementica,

Apis melifera monticola, Apis melifera litorea and Apis melifera abyssinica.

5.2.1. PHENOTYPICAL CHARACTERIZATION

Phenotypic characterization of AnGR is the process of identifying distinct breed

populations and describing their external and production characteristics in a given



environment and under given management, taking into account the social and

economic factors that affect them. The information provided by characterization

studies is essential for planning the management of AnGR at local, national,

regional and global levels. Characterisation of livestock breeds has been based on

description of morphological characters such as horns, ears, coat colour, body size

and production and reproductive traits. Since livestock breeds in developing

countries have not been subjected to selection for specific traits, considerable

phenotypic variation is observed within and among populations with regard to size,

horn and ear types and coat colour. Furthermore, most productive traits are

polygenetically inherited and are influenced by environment effects, sometimes

with a genotype x environment interaction. This leads to some inconsistencies in

the classification of the various populations into breeds or strains. Therefore,

reliance on phenotypic characters as the basis for characterisation of breeds for

sustainable utilization and conservation may be misleading.

5.2.2. MOLECULAR GENETICS CHARACTERISATION

DNA marker data provide useful information on the origins, relationships, genetic

diversity and gene pool development of domestic animal breeds. The data help to

identify those breeds that are genetically distinct. Genetically differentiated breeds

can carry genes and gene combinations of economic and scientific importance and

which determine an animal's capacity to adapt to particular environments.

Molecular genetic characterisation is factual and precise. It is in this sphere that

molecular biotechnology has an important role to play. Genetic characterisation of

livestock species involves estimation of the genetic uniqueness of the breeds or

strains and their evolutionary relationships. This can provide information on

which of the populations represent homogenous breeds or strains and which are

different.

Such knowledge will enable decision-making regarding the choice of breeds or

strains for conservation.



Chapter 5: Breeding Programs

The aim of animal breeding is to genetically improve populations of livestock so

that they produce more efficiently under the expected future production

circumstances. Genetic improvement is achieved by selecting the best individuals

of the current generation and using them as parents of the next generation. To

select the best animals one needs to define explicitly what is meant with "best".

This means that it is necessary to specify the direction in which we want to change

the population. Defining the breeding goal is the first step when designing a

breeding program. It is useless to design a breeding program if there is no idea of

the desired genetic change.

NB. A breeding program is the organized structure that is put into place to

genetically improve livestock populations.

Successful genetic improvement requires breeding programs to have (at least) the

following components:

A system to record data on selection candidates. Without data on selection

candidates it is impossible to identify the best individuals.

Methods and tools to estimate the genetic merit (breeding value) of selection

candidates. This step is called the "breeding value estimation".

A system to select the animals that become parents of the next generation, and

mate them to produce the next generation.

A structure to disseminate the genetic improvement of the breeding program

into the production population. In most cases, the breeding population and the

production population are (partly) separated. Since the aim is to improve

livestock production, genetic improvement created in the breeding population

should be disseminated into the production population.

6.1. The breeding goal



The breeding goal, or breeding objective, is the starting point of animal breeding.

Broadly speaking, the breeding goal is the direction in which we want to improve

the population. The choice of the breeding goal affects the structure of breeding

programs. Broiler (chicken for meat) breeding programs for example differ from

layer (chicken for egg production) breeding programs because improvement of egg

production requires another breeding program than improvement of meat

production.

The breeding goal has a number of characteristics.

1. The breeding goal is a combination of traits. It specifies the relative

importance of each trait. In principle, all traits of importance should be included in

the breeding goal. Thus the breeding goal only depends on the importance of a

trait, not on its genetic parameters. An important trait of low heritability should be

included in the breeding goal, whereas unimportant traits should be left out,

irrespective of their heritability.

2. The breeding goal should aim at the future. Animal breeding is a long-term

activity. It takes a long time before genetic improvement due to selection is

expressed in the production population.

3. From an operational point of view, the breeding goal should ideally summarize

all traits in a single criterion. A single criterion to express the quality of

selection candidates is convenient because animal breeders can simply rank

their selection candidates on this value and select the highest-ranking

individuals. A breeding goal expressed as a single value can be obtained by

weighting all traits by an (economic) factor, so that the breeding goal is a sum

of breeding values weighted by their (economic) value.

Questions should be raised in developing breeding programs are like:

what market the breeding goal is aimed at;

whether the breeding goal should be based on the competitive position of the

breeding company or on an economic model of the production herds

Existence of political or market circumstances such as production quota that

affect the breeding goal.



In Western countries, breeding goals primarily include economically important

traits such as milk yield, meat production and egg production. In addition, breeds

are often specialized for a single purpose; dairy breeds are kept for milk

production and beef breeds for meat production, layers for egg production, broilers

for meat production. In developing countries however, the situation is quite

different, because livestock is often kept for auto-consumption and not to produce

for a particular market.

========================Message==========================

NB. The breeding goal specifies which traits should to be improved, in which

direction and the relative emphasis given to each trait.

==========================================================

In animal breeding, there are two common approaches to define breeding goals.

The first approach is to express breeding goals as a weighted sum of economic

values and breeding values. In this approach, economic weighting factors of traits

(economic values) are based on an economic model of the production system. The

second approach is to express the breeding goal as a set of desired gains for each

trait. The desired genetic gain for each trait is based on marketing and commercial

considerations of breeding companies. In many cases, desired gains are based on

maximizing the market share of the breeding company in the time frame.

Breeding goals based on economic models of the production system:

When breeding goals are based on an economic model of the production system,

the economic value for each trait is determined by modeling the effect of that trait

on the profit of a production herd. The breeding goal (H) is expressed as a

weighted sum of true breeding values and economic values,

NB. Breeding goals can be expressed in terms of economic values, which

express the increase in due to a single unit improvement of a trait, or as desired

genetic gains.

6.2. Components of breeding programs

1. Data recording and collection: Estimation of breeding values requires

phenotypic data on selection candidates. Thus a system has to be set up to



routinely record data on selection candidates. The way data is collected depends

on the species and the traits in the breeding goal. Dairy cattle breeding schemes

therefore have a system to record data on daughters of test bulls. Milk yield of

those daughters is recorded on common dairy herds, meaning that farmers are

involved in the data recording. In beef cattle breeding, growth performance of

bulls can be recorded on the selection candidates themselves, meaning that

progeny testing is not necessary. In beef cattle breeding, data collection therefore

takes place at testing stations where the performance of selection candidates is

recorded.

2. Selection and mating: Selection and mating takes place after breeding values are

estimated. Selection refers to the process of choosing parents to produce the next

generation, whereas mating refers to the pairing of selected individuals. Thus

selection precedes mating. The selection process determines the genetic

improvement of the population over time, whereas the mating process determines

how maternal and paternally derived alleles are combined within individuals.

3. Dissemination of genetic progress: In most species, the breeding and

production population are distinct. Genetic progress is created in the breeding

population, but the final aim is to improve livestock production in the entire

population. Thus genetic improvement created in the breeding population has to

be disseminated into the production population. In dairy cattle, the breeding and

production populations are not strictly separated. Superior cows from the

production population can enter the breeding population, meaning that they are

selected as bull dams. Genetic progress created in the breeding program is

transferred to the dairy farms by the sale of semen of progeny tested bulls to the

farmers. The sale of semen is the primary source of income for dairy cattle

breeding companies.

=======================Message========================

A breeding program has the following components: i) a data recording

system, ii) methods and tools for breeding value estimation, iii) a selection

and mating

4. INBREEDING AND RELATIONSHIP



All the living beings are interrelated. The relationship between any two

individuals is due to procession of some common genes they have because

of immediate or remote ancestor in their decadency or lineage or heritance.

It is the brood sense of relationship. But for practical purpose any two

individuals are said to be related if they have one or more ancestors in

common at least in first six generations. After six generation because of

halving of remote ancestor‟s hereditary materials two individuals would

have little genetic relationship.

The relationship is categorized into three groups

(a) Direct relationship

(b) Indirect or collateral relationship

(c) Combination of direct and indirect relationship

Direct relationship: If occurs between individual and its ancestor or

between individual and descendant. It arises when out of two individuals

one is direct ancestor (parent) other is descendant (progeny). The

relationship between the parent and offspring is 50 percent or 0.50 because

one half of the offspring‟s genes are obtained from one of the parent i.e.

50% of parental and offspring‟s genes are same. The parent offspring

relationship is the simplest one.

Indirect or collateral relationship: This kind of relationship exists when

relatives are not directly related to each other or descendant in lineage

because they are not ancestors or descendants of one another. However

they have one or more ancestors in common. e.g. Full sibs, half sibs,

cousions etc where in both the individuals, receive common genes from

their ancestors..

Combination of direct and collateral relation ship

This type of relationship is seen when an outstanding individual is mated to

is descendant and also to its collateral relatives. If the ancestor appears in



pedigree more than once relationship between the individual and ancestor

in question is always greater than if ancestor had come only once in lineage

or pedigree of an individual

Measurement of inbreeding

Inbreeding (mating of related animals) has many effects on genotype and

phenotype. Inbreeding increases the homozygocity and it decreases the

heterozygocity. All the good and bad phenotypic effects are because of this

increased homozygocity or loss of heteroyzyocity. Therefore it is important

to measure amount of inbreeding of an individual or herd. The term

inbreeding coefficient (F) is used for this purpose which measures the

increased homozygocity. Homozygocity, a likeness of two genes may by

state (chance). They are two randomly drawn genes from population and by

chance they are alike. It is known as identical by state. Two genes of an

individual may be alike by descent. It is because of mating of relatives.

Alikness arise from replication of same genes from common ancestor. It is

known as identical by descent. Thus inbreeding coefficient is probability

that two alleles at a locus in an individual are identical by descent. It is

measure of decrease in proportion of heterozygous genes over what was

present before inbreeding is practiced. It is always a measure relative to

some starting point, some generation back for which F is considered as

zero, It two individuals have no common ancestor in past six generation.

5. METHODS OF GENETIC IMPROVEMENT

Selection

In random mating in large population, in absence of selection, mutation,

migration the gene frequency remains constant. Hence we assume that each

individual of the population contribute equal number of gametes to the

population. Each individual will contribute to next generation in proportion



of frequency of genotype in current generation. Since there is no change of

gene frequency no change of phenotypic properties is expected.

But the nature or men do not allow each individuals to contribute equally to

the gamete pool. Nature allows most successful genotype to multiple and

men allow most useful genotype to multiply. Therefore certain individuals

are preferred to others in production of next generation. Thus selection is

choosing of parents of next generation either by nature or by men. It is

designation of parents of next generation. The process of differential

reproduction among the individuals of different genotype is known as

selection.

Selection

Natural selection Men made selection

(Artificial selection)

The natural selection depends up on the genetic differences among the

individuals in fitness characters such as disease resistance. Libido, mating

behaviors, anatomical and physiological superiority. It is the survival of the

fittest. Only strong and these adapted to environment survive and produce

large number of offspring‟s.

In artificial selection breeder determines which animal to reproduce, which

will be retained for replacement, how long they will be allowed to remain

in population.

Both natural and artificial selection do occur simultaneously in a

population. They may influence the same or different traits same or in

opposite direction. Selection is practiced by nature or men at any stage of



life. Some are not allowed to born some are born and die before they

reproduce, some are culled because of their bad pedigree, some are culled

after their own performance and some are culled after knowing their

progeny performance.

Objective of selection

1. To improve the overall productivity which includes utility, survivability

etc

Principles of selection

1. Variation is basis of selection.

2. Selection is effective when the traits selected are heterozygous.

3. When a race / breed / herd becomes homozygous for certain trait selection

no longer improve it.

4. Selection should be based on hereditary variation and not on environmental

variation.

5. Selection does not create any new genes.

6. Selection increases the frequency of desirable genes.

Selection will be effective and meaning full if systematic recording is

practiced. But even without the knowledge of Genetics selection was

highly effective. The difference between the performance of breeds of

present day and primitive type of animals is the best of example of effect of

selection.

Type of selection

Directional selection: The breeder select the individuals to be the parents

of next generation whose phenotype are more nearly approach a maximum

(milk yield) or minimum (back fat thickness in pigs) for some trait. Other

individuals with poorer phenotype are not allowed reproduce. If the trait is

heritable than the part of phenotypic superiority of selected parents will be



passed on to the next generation. Next generation will be above the

population average. The favorable genes frequency will be increased.

Therefore the effect of directional selection based on phenotype variation is

due to genotype. It will increase the gene frequency of favorable genes and

decrease the gene frequency of undesirable genes. Directional selection is

practiced utilizing the records of ancestors, individual, progeny, collateral

relatives.

Factors affecting the selection progress

Many physical, biological and management factors affect the selection

progress.

1. Ability of the breeder: Progress of selection depends upon the ability

breeder to select the superior breeding stock. He should have a definite goal

(objective) in his mind and should not change it often. He should have

accurate records for comparison.

The popular type of this year may not have the same favor in coming years.

So the selection progress can be slowed down. Hence should have a plan

well in advance for the future trends and need of the people

2. Foundation stock: Selection will be ineffective if the foundation stock

is poor. If the genes which are desirable are not found in the foundation

stock or are very rare then the selection will be powerless. In that case

the desirable genes have to be introduced from outside (out breeding)

3. Level of performance: If the population performance is uniform the

difference between the selected and rest will be less. Similarly the selection

becomes ineffective if the herd average for that trait is very high. Then it

will be difficult to find animals that exceeds the herd average. This occurs



due to long time selection and decrease in genetic variability. By

outbreeding (introducing new genes) and changing the environment

variation can once again brought about for further selection.

4. Number of traits considered for selection: Simultaneous selection for

large number of traits reduce the selection intensity for any one trait. Only

those traits which are economically important should be considered. Less

important traits such as color, shape of the ear, shape of horn etc which

have no influence on the performance should not be taken for consideration

during the selection.

5. Heritability of the trait: The qualitative traits are more heritable than

the quantitative traits. If the heritability of coat colour is one (100%) this

character is completely inherited from parent to offspring. If the h2 of the

trait is high selection progress will also be high because a large portion of

selection difference is due to heredity and not due to environment. Any

difference in environment can not be transmitted to next generation.

6. Selection differential: Larger the selection differential more will be the

selection progress.

7. Length of time selection is practiced: Improvement of performance traits

in large animals is slow and takes long period of selection. Further progress

in single generation is likely to be masked by environmental effect. It takes

few generation to note the real progress.

8. Generation interval: By reducing the generation interval one can increase

the selection progress.

9. Genetic correlation among the traits selected: While selecting for two

traits at time if improvement in one traits brings about the improvement in

another also the total progress will be more. e.g. Rate of gain and efficiency

of gain. If the two traits are negatively correlated than the total progress

will be less or nil.



e.g. Milk production and draft capacity.

Concept of Breeding value and transmitting ability

Suppose in beef cattle herd selection is based on the yearling weight

Herd average 200 kg

Selected bulls yearling wt 250 kg

Selection differential 250 – 200

= 50 kg

Heretability of yearling wt 0.50

Genetic gain 50 x 0.50

= 25 kg

Average of the progeny of 200 +25

this bull = 225

Aids to selection

There are several sources of information available to increase the selection

accuracy or probable breeding value of the individual. Some information is

from individuals own performance some are from their relatives

Individual selection (mass selection)

Selection is based on the performance of individual itself. The phenotype

of individual is the sole criterion for estimating his genotype (Genetic

merit). This is also most commonly used basis for selection in livestock. It

is effective when the heritability of the trait is high, indicating that the trait

is greatly affected by additive gene action. High h2 estimate also suggest

that phenotype strongly reflects (correlated with) genotype. Further the



individuals that are superior for particular trait should also poses desirable

genes for that trait and should transmit these genes to their offsprings. But

one should provide standard environment to distinguish between the

genetic and environmental effects.

Advantages:

.1.Simple since the characteristics such as milk yield, growth rate, fleece wt

etc can be directly evaluated from the individual itself.

2. Selection can be made even without the knowledge of the pedigree.

3. Less time consuming compared to progeny testing.

4. All the animals can be evaluated, whereas in progeny testing only

limited number of animals can be evaluated.

5. Can be used as preliminary selection before progeny testing.

Disadvantages

1 Many of the economically important traits are sex limited and hence

expressed only in one these sex. (Female). Therefore selection of males

cannot be based on their own performance for the traits (milk yield egg

yield)



2 .Records of milk yield, egg yield etc are available only after the sexual

maturity. Therefore selection has to be postponed till such time.

3. Slaughter traits such as carcass quality, dressing percentage etc can be

assessed only after

Slaughter of the animal. Therefore it is of no help in selecting for these

traits.

4. In case of traits which have low h2 individual merit is a poor indicator of

the genotype.

Therefore the improvement from individual selection will be less for such

traits. If the superiority of performance of an individual is due to

heterozygosity it will not be transmitted to the offspring.

Methods of selection

1. Tandem method:

Selection is practiced for only one trait at a time until satisfactory

improvement is done in this trait. Then the second trait is considered for the

selection and so on. If there is a positive correlation between the first trait

selected and any other trait both will improve. If there is negative

correlation, progress in one trait is affected by a decrease in other and will

nullify the effect e. g milk yield and fat percentage, Heat tolerance and milk

yield.

Disadvantages.

Least efficient method

More effort and time consuming

Negative correlation between several economic traits will nullify the

improvement



2. Independent culling method

Selection is practical for two or more trait at a time. For each trait a

minimum standard is set. Animal should meet standard for selection.

Failure to meet the set standard for any one trait will disqualify the animal.

e. g

Character Birth wt AFC Milk yield fat %

Min. standard 30 kg 30 m 2000 kg 5 %

This has been usually used in past for type and confirmation traits (color,

size, horn) in show cattle regard less of economic value

Advantage

1. Selection for more than two traits at a time will bring about simultaneous

improvement.

2. Animal can be culled at an early age for failure to meet the minimum

standard thus reduce The cost maintenance.

Disadvantages

1. An animal is culled for failure to meet the minimum standard set for one

trait although it is superior in other traits. (4.5 % fat 3000 kg milk).

2. Animal may culled at an early age for its failure to meet the minimum

standard without giving chance to reveal superiority in later stage of its life.

(i e a female calf weighing 24 kg will be discarded. Without giving chance

for future i.e production.

Selection index method (Total score card method)

In this method value (marks or score) is separately determined for each of

the trait selected for and these values of each trait selected is added to give



a total score for all the traits. The animals with higher total score are

selected.

The value for each of the traits defendants upon

a) Relative economic value of the trait

All the traits selected are not equally important and carry equal marks

b) Heritability of the traits. Higher the h2 more the value

c) Genetic correlation with other important trait

Advantages

1. One of the advantage of this method is even though animal is slightly

deficient in one trait and if it superior in other trait it will be saved.

2. The efficiency of this index selection is more than that of independent

culling level and efficiency decreases as more traits are involved. If the „n‟

is number of traits then an index is n times as efficient as independent

culling level

Disadvantages

1. Construction of selection index under is highly complex

2. The genetic parameters (heritability, correlation) and economic values

are not constant for all the populations and in all the time and depends on

many factors thus lead to revise the index.

Selection based on progeny performance (progeny testing)

It is the estimation of breeding value or genetic worth of an individual from

the study of the performance of its offsprings. It is being increasingly used

as an aid in estimating the genetic worth of an individual. The idea of

progeny testing is not new. About 2000 years ago it was advocated by



Varro of Rome. Robert Bakewell used the outstanding sires after knowing

the performance of their progeny in 18th century. the dams.

Principle: The principle underling the progeny testing comes from the

sampling nature of the inheritance where each offspring receives a sample

half of the gene from its parent. Each additional offspring receive another

independent sample from same source.

Selection based on collateral relatives:

Collateral relatives are those individuals who are not directly related either

as ancestor or progeny.

e. g full sibs, half sibs

They do not contribute any gene to their relatives. But they have certain

common genes which they have received from their common ancestors.

Thus average performance of collateral relatives gives an indication of

genetic makeup of an individual. More closely collateral relatives are

related to the individual more accurate is the estimation of its genetic

worth. Therefore selection based on the information of full sibs is more

accurate than that of half sibs.

Advantages of selection based on collateral relatives:

A. For sex limited traits

Selection of bulls based on milk production of his half sibs, full sibs.

B. For slaughter traits (carcass traits)

Slaughtering the half sibs / full sibs to evaluate the carcass quality

c. Less time consuming compared to progeny testing

d. Less generation interval compared to progeny testing



e. Useful for traits of low h2

Though less accurate than progeny testing the generation interval is less in

selection based on collateral relatives. Therefore it may be almost equal to

progeny testing in genetic improvement obtained.

Family Selection

In livestock selection, family can be classified into three types.

1. Sire family;

These are the offspring of one sire out of different dams, may be born in

same year or born over number of years.

2. Dams family: These are the offspring‟s of one dam out of different sires

may be born in same year or in different years.

In case of cattle and sheep superovulation of dam and Invitro fertilization

by sperms of different sires. Can give this type of family.

3. Sire and dam family

These are the offspring‟s by one sire and one dam. These offspring can be

obtained by in same year or in different years.

Therefore family is usually made up of full sibs or half sibs. The families of

remote relationship being of little practical importance. Full sibs‟ family

selection is practiced when reproduction rate is high (pigs, poultry) and half

sib family selection when reproductive rate is low (cattle, sheep). However

in poultry the sire family selection is more efficient than the dam family

selection when h2 is near about zero and less than 0.10. Since h2 of egg

production is approximately 0.10, sire family selection is usually practiced

for improving the egg production.



Mating systems

The mating systems govern the breeding plans that are aimed to harness the

favorable gene combinations to maximise the net profit to the farmers.

Generally mating systems are executed immediately ofter successful

selection of suitable parental genotype to produce progeny of the next

generations. Therefore mating system is one of the ways open to the

breeder for

a) Changing the genetic constitution of progeny generation over

population.

b) Improvement of the performance of progeny generation over base

population.

General objectives of mating systems

To produce the future progeny of good genotype to make further profit.

To bring together the desirable gene combination after selection

To bring the genetic uniformity

To enhance the relationship

To Ancash the effect of heterozygosity

To overcome the hereditary defects

To form a base for synthesis of strain / line / breed.

Effects of mating systems:

Alter the gene frequency (Hardy Weinberg equilibrium is altered.)

Cause genetic uniformity / purity / and therefore increase the pre potency

Cause the heterozygosity (heterosis)



Broad classification of mating system

Based on genetic relation ship

Random mating Nonrandom mating

Inbreeding Out breeding

Random mating: It is system of mating in which individual of one sex is

equally likely to mate any other individual of opposite sex in a given

population. It is also called as “Panmixie”

Nonrandom mating: It is also known as “Selective mating” in which case,

the selected male is mated with selected female.

Out breeding: It mating of genetically less closely related individuals than

average of the population. It is known as out breeding.

Inbreeding

Mating of closely related individuals compared to average of the

population is known as inbreeding. Inbred individual carry more of

identical genes by descent.



Objective

To increase the relationship to an outstanding sire or dam.

To increase Homozygocity

Genetic purity

Uniformity

To eliminate the recessive undesired alleles

To form distinct lines/strains/family or seed stock from highly

heterozygous population

To increase the prepotency (ability to produce its on type) due to increased

homozygocity.

Disadvantages

Too many progeny have to be

slow increase of homozygocity

Discarded because homozygocity of recessive genes.

Progeny become susceptible

to disease, reproductive problem,



Chapter 7: Selection and Genetic Change

The previous chapters have introduced basic animal breeding theory and have

shown how one can estimate the genetic merit (breeding value) of individuals. This

and the following chapter will show us how that information can be used to

genetically improve livestock populations and how one can quantify the

expected genetic improvement. The animal breeder has two tools to genetically

improve his populations: selection and mating.

7.1. Selection

In animal breeding, the aim is to genetically improve livestock populations by

exploiting genetic differences among individuals. Genetic improvement is

achieved by selecting individuals that are genetically superior to the rest of the

population. The term "selection" refers to the process of choosing parents to

produce the next generation. The challenge for the animal breeder is to select

genetically superior parents to produce the next generation of offspring, so

that only the alleles of those individuals will be passed on to the next generation.

Similarly, to prevent alleles from genetically inferior individuals from being

passed on to future generations, they should be avoided as parents. In addition,

one may decide to produce many offspring of the very best individuals and fewer

offspring of sub-optimal individuals. In that case, the very best individuals will

contribute more alleles to the next generation than the sub-top individuals. Thus

the process of selection determines which alleles are passed on to future

generations and therefore determines the genetic composition of the population in

the future. It is important not to confuse selection with mating. Selection refers to

the choice of parents, whereas mating refers to the "making of pairs" among the

parents that are already selected. Thus selection precedes mating.

Selection does not create new genes, but increases the proportion of favourable

genes in the population. The gains are accumulated when we continue to select the

best animals in each generation. A continuous, long-lasting genetic improvement

in traits included in the breeding goal is thus achieved.



There are two kinds of selection, natural selection and artificial selection.

Natural selection is the process of survival and reproduction in natural populations.

In populations in the wild, the individuals that fit best to the environmental

conditions produce the most offspring. As a consequence, those individuals

contribute the most alleles to the next generation. Natural selection therefore

favours a combination of viability and reproductive ability, i.e. fitness traits.

The selection done under human control to obtain genetic improvement of traits in

domestic animals is called artificial selection. Fitness traits, such as fertility and

disease resistance are usually included in this selection, but large emphasis is given

also to many other traits, such as production traits, productivity, product quality,

performance traits and longevity. Selections of the cows with the highest milk

production or of the fastest growing chickens are typical examples of artificial

selection.

Selection can be performed both between and within populations (e.g. breeds).

To screen animal populations and thereafter use those that have characteristics in

line with a desired breeding goal can be a way to get results quickly, assuming the

populations can be compared properly. For continuous and long-lasting effects,

however, it is necessary to conduct selection within populations. This is what is

normally meant by selection for genetic improvement.



Figure 7. 1. Illustration of how selection effects are accumulated and

maintained.

From the above figure we can see that:

Using selected animals from the base population as parents results in an

increased genetic level of the animals in the next generation (see the column

for generation 1).

The selection effect obtained through selection in generation 0 is maintained

also in later generations (see the row for selection effects from generation 0).

Selecting superior parents also in subsequent generations further raises the

genetic level of each generation.

The selection effects from each generation are accumulated. Thus, the

genetic level of animals in generation 5 is built up by selection effects from

all previous generations (see the column for generation 5).

The genetic trend per generation is illustrated through the line.

The driving force for genetic improvement is of course the genetic superiority

achieved by the selection of parents, but also other factors, such as generation

intervals and differentiated use of selected breeding animals, have an impact. One

should also remember that additive genetic variation is a prerequisite for any

selection effort to be successful. The animals in the population must be genetically

different with regard to a specific trait. Otherwise it will not be possible to select

individuals that are better than others!

7.1.1. Selection strategies

The traits we want to improve in a population are defined in the breeding goal. A

few of the goal traits might be influenced by simply one or a few alleles, which

means that the true genotype often can be determined (e.g. through a DNA test)

and it is then easy to select the desired genotypes. The majority of goal traits,

however, are quantitative in nature, i.e. influenced both by genes at many loci

and by environment. These traits are often normally distributed. Selection is then

commonly based on predicted breeding values, which in turn are based on



phenotypic values and knowledge of heritability, genetic correlations, genetic

relationships, economic weights, etc.

Selection

Directional selection is the most common type of selection. It means that an

extreme fraction of the individuals are selected. If a high value for a trait is

desirable, then we select the animals with the highest values, e.g. those with high

growth rate, milk yield or performance score. If a low value is desirable, then we

select animals in the opposite fraction of the normal distribution, i.e. the animals

having low values, e.g. for back-fat thickness, disease incidence or time to run a

race.

Stabilizing selection means that we select a middle fraction of the animals and

avoid selecting the extremes. In this type of selection it is the optimum values that

are desirable. Examples could be birth weight and quality traits, such as meat

tenderness. It is possible also that in species with large variation in litter size one

wants to avoid selecting animals giving very small or very big litters.

Selection within a population is usually applied in several stages; this is

sometimes called stepwise selection.

The first selection event might be based entirely on pedigree information

(usually the average of the parents‟ breeding values).

The next events might occur when information is available on animals

themselves, and maybe also on sibs; one selection round on traits expressed

fairly early in the animals‟ lives, e.g. growth rate,

Another round on traits expressed later, e.g. fertility or performance.

A fourth selection round might occur when in addition to previous

information there are also progeny results at hand.

There might also be one step for selection of elite animals as parents to the next

generation of males to be used in artificial insemination. The best animals in

each round of selection are retained to the next selection event, while the ones

that are not selected might be culled, or they might be used as production

animals, or even as parents to non-elite breeding animals.



Measuring and keeping records of important traits, and also predicting breeding

values without bias and with a high precision, is fundamental for a functioning

selection program. The accuracy by which we are able to rank the individuals

determines the success of a selection among them.

7.1.2. Selection schemes

Various schemes are adopted for the selection of the best animals into breeding herd. In

the simplest methods, animals can be selected on the basis of:

a) their own performance records (individual selection or mass selection),

b) progeny records (progeny testing)

c) their family mean (family selection) or pedigree selection).

Literally all of these methods of selection use the available information about each

animal‟s breeding value in order to determine the genetic worth of the animals through

development of an index of merit.

a) Performance Testing

Performance testing is basically selection of genetically superior animals on the basis of

their own records of economically important performance traits. In this method, animals

are tested either on-station or on-farm. In each case, performance data for the traits

under consideration are recorded and analysed to estimate the breeding values for the

animals. If selection is based solely on the basis of the animal‟s phenotypic values, it is

also referred to as individual selection. There are some conditions that must be met for

maximum response to be attained from this scheme: -

The production traits must be accurately measured and correct records of performance

maintained. Inaccurate measurements, just like inaccurate records, result in misleading

predicted breeding values resulting in poor performing animals being selected for

breeding. This will impact negatively on overall productivity and performance of the

farm when the cost of maintaining a wrongly selected animal

The breeder must ensure that the animals being considered for selection are from the

same contemporary groups that had equal provisions in terms of age, sex, management

including feeding, treatment, vaccinations



All predictable fixed effects (environmental factors) should be pre-adjusted for before

genetic evaluation of the animals is carried out.

If all the above conditions are met, performance testing provides the simplest selection

scheme and apparently gives the most rapid response to selection

However, this scheme has its own

Disadvantages: -

Some traits are sex-limited being expressed only in one sex. As such, performance

testing cannot be conducted in both sexes and this has a tendency to limit the progress

of genetic improvement

Some traits can only be measured very late in life when the animal is approaching the

end of its economic value. In beef cattle breeding, some traits like carcass quality are

measured after slaughter and thus such records cannot be utilized in performance

testing

This scheme is of little significance for traits of low heritability, because of the very

low genetic progress realized from selection on its basis.

b) Progeny Testing

This is a form of family selection that is widely used in animal breeding. This method is

based on the principle that the mean performance of a progeny group should give a

reliable indication of the estimate of the breeding value (EBV) of one or other of its

parents, since each offspring receives a random sample of genes from both parents (half

of them from each parent). As such the selection criterion with this system is the mean

value of an individual‟s progeny. Progeny testing estimates the breeding value of one

parent, on the basis of performance of its progeny. Dams are not usually progeny-tested

because of the limited number of offspring that they produce in their lifetime.

Procedure for progeny testing

Potential parents are mated to a random sample of dams within a herd;

The resultant offspring (progeny) are measured for performance on the traits

under consideration;



On the basis of the progeny group average, and after weighting for the different

number of progeny per parent, the breeding parents are selected from the group

potential parents.

Selected parents are mated to produce a second batch of progeny which become

the next group of parent to be progeny tested.

Limitations of progeny testing

There is a lengthened generation interval since the selection of the parents cannot

be carried out until the progeny have been measured.

There is possibility of generations overlapping and this further complicates the

evaluation of the parents.

There is a possibility of ambiguity since the progeny will be tested just when the

parents are being tested. There is a real possibility of using both as parents.

c) Pedigree selection

The pedigree of an animal is a record of all the ancestors, recent and remote that are

related to the animal under consideration. In this respect, knowledge of the genealogy of

the animal alone may be of limited use in pedigree selection but rather, the productivity

of all these ancestors to the individual animal. Pedigree selection therefore estimates the

breeding value of an animal on the basis of production performance of its ancestors. If the

performance of an individual animal is known with precision, it may not be wise to carry

out pedigree selection but rather individual selection.

Pedigree selection is only useful when: -

Progeny performance data are not available;

The animals to be selected are so young such that their individual merit cannot be

ascertained with any degree of certainty;

Selection is being made for animals with comparable individual merit.

Pedigree selection has several advantages including that it is: -

Relatively less expensive to carry out since it uses only records.

Useful for initial selection of those traits that are expressed in one sex only.

Selection can be carried out early in the life of the animal to be selected.

The disadvantages of pedigree selection include: -

It puts undue emphasis on relatives, particularly remote relatives, resulting in a

reduction in the intensity of individual selection.



It is biased towards progeny of favoured parents having been selected previously

7.1.3. Multiple trait selection methods

The goal of multi-trait selection is to increase the net merit of the population.

Thus, one important factor in designing multi-trait selection schemes is the relative

economic value of a unit genetic gain in each trait included in the selection

program. The most effective way to account for differences in the economic worth

of each trait is to weight each trait by its economic value so that each component

breeding value in the aggregate breeding value is improved in proportion to the

economic gain expected.

There are three recognized approaches to multi-trait selection, although many

operational selection programs combine parts of more than one method to achieve

various breeding goals. The three selection methods are:

a) the tandem selection procedure

b) independent culling method

c) the index selection procedure,

a) Tandem Selection

This method of selection involves selection for each trait singly, but is

sequence. Selection is first carried out for the most important trait, based on

economic value of genetic gain and predicted genetic gain, for a given number of

generations. Once the goals for the first trait have been achieved, selection effort is

targeted to the next most important trait, and carried out for specified number of

generations. The process can continue indefinitely, for any number of traits. Often

in practice, the tandem method is superimposed on top of the other two methods of

selection to provide long-term flexibility in changing traits targeted for selection



as market conditions change. As is true for all three methods of selection, tandem

selection has advantages and disadvantages.

Advantages of Tandem Selection:

It is the simplest of the three methods and requires the least amount of detailed

information. Prediction of selection response is simple since response for each trait

in sequence can be predicted using the simple equation for truncation selection on

a single trait. In addition, the method can take advantage of favorable genetic

correlations with other traits, allowing correlated genetic gain in secondary traits to

offset the cost of selection.

Frequently, the tandem method is applied when a population is first placed

under domestication or a new breed is under initial development. Under such

conditions, little genetic information is available for traits because of the newness

of the population so the simplest approach is to choose a single trait with high

economic value to initiate the program. As more information is acquired regarding

additive genetic variances and phenotypic and genetic correlations, the program

can be modified to address other important traits.

Disadvantages of Tandem Selection:

It is difficult to set a goal representing the desired end point for selection on each

trait in the sequence. Tandem selection can have a major negative impact on net

merit of the population if unfavorable genetic correlations exist between the trait

under selection and any other trait important to net merit.

b) Independent culling level

This method is used in multiple trait selection. The implementation of this method

based on setting a minimum level of performance for each trait included in the

selection program. The selection procedure is simple truncation selection for each



of the traits based on the culling level specified for each trait. The culling levels are

said to be independent because once the culling levels are established for each trait

selection proceeds on each trait without reference to the performance of individual

animal may exhibit for other traits. Culling is a procedure used to remove under-

performing animals from a production herd so culling decisions is based on some

estimate of producing ability.

Example: Consider a program for the selection of heifer replacements for a beef

cattle population, designed to increase yearling weight but to keep birth weight

below at maximum accepted level. Selection for yearling weight may be desirable

because increased weight would reflect rapid growth rate and would increase the

number of heifers that could be bred for the first time at one year of age without

impairing their long-term reproductive performance. On the other hand, controlling

or reducing birth weight would reduce parturition problems in the herd.

Advantages of independent culling method

relatively easy to apply because the procedural rules are very direct; determine the

culling levels and select all individuals meeting or exceeding the culling levels.

The method can be very effective for qualitative characters such as coat color,

general body conformation or physical soundness.

The method is also convenient when selection can be carried out in steps over the

life time of the animal.

This approach allows flexibility in determining the importance of the various traits

to net merit by adjusting the selected proportions to achieve the desired final result

(based on economic values and predicted selection response).

Disadvantages of independent culling method

There only two difficulties in applying the independent culling levels method of

selection.

It is difficult to establish culling levels that truly reflect the economic value and

expected selection response.



Preventing arbitrary modifications to the culling levels, because of short-term

changes in market conditions or the attitude of the breeder.