19
Pergamon 0273-1223(95)00422-X War. Sci. Tech. Vol. 31, No. 10, pp. 1-19, 1995. Copyright @ 1995 IAWQ Printed in Oreat Bntain. All rights reserved. 0273-1223195 $9'50 + 0-00 NUTRITION, ANIMAL PRODUCTION AND THE ENVIRONMENT A. Rerat* and S. J. Kaushik** Centre de Recherches de Jouy, INRA, 78350 Jouy-en-Josas. France •• Laboratoire de Nutrition des Poissons. Unite Mute INRA-IFREMER. Station d'Hydrobio!ogie. INRA. 643/0 Saint Pee-sur-Nivelle. France ABSTRACT Wi!b increasing demographic grow!b, !bere will be an ever increasing demand for greater food production over !be turn of this century. Seen from today's productivist point of view, this is not too difficult a challenge to meet. Besides socio-economic and geopolitical considerations, it is now of the utmost importance to consider any such increase in food production from a global environmental perspective. Man-made changes to the environment are numerous, some perhaps irredeemable. The essential human activities of agriculture, animal production and fisheries also affect !be environment and some quantitative data are available on sucb impacts. Eacb progress in increasing agricultural resources (reclaiming new land areas for agriculture, increase in land productivity, intensification of animal production etc.,) is not without disadvantages (deforestation, pollution of underground water !brougb different contaminants). Imensification of land animal production, facilitated also by progress in biotechnological methods leads to increased contamination of the natural food chain and to the concentration of effluents. Aquatic production, currently undergoing tremendous progress, is also facing several sucb dangers: over-exploitation of natural resources; slow disappearance of natural breeding grounds; increased pollution of water througb industrial, agricultural and aquacultural activities. Every such menace to the future of food production bas its solution. Even !be applIcation of already available knowledge can prevent further deterioration of our land, air and aquatic environment for sustained production. But, local socioeconomic pressures and lack of concern or education often prevent us from obtaining !be ideal balance between food production and environment. KEYWORDS Global food production; environment; nutrition. INTRODUCTION The world food production is currently capable of supporting all the requirements of humans. Food production has been increasing faster than the world population over the last ten years (24 vs 20%), thanks to efforts in several fields. The per capita food energy intake has increased by a world average of 12% from 1965 to 1985 (FAO, 1988). The average increase recorded in developing countries (19%) conceals widely disparate situations, since the increase only amounted to 4% in Mrica, and the daily per capita intake actually decreased between 1975 and 1985 in some sub-Saharan countries. The most basic requirements (8 MJ) were not met in 1989 in nine developing countries, totalling 196 million inhabitants. The daily 10.5 MJ limit was exceeded, however, in 35 developing countries, totalling 1.88 billion inhabitants. It should be stressed that despite improvements, almost one billion people out of the current 5.5 billion populating the

Nutrition, animal production and the environment

  • Upload
    a-rerat

  • View
    217

  • Download
    2

Embed Size (px)

Citation preview

Page 1: Nutrition, animal production and the environment

• Pergamon

0273-1223(95)00422-X

War. Sci. Tech. Vol. 31, No. 10, pp. 1-19, 1995.Copyright @ 1995 IAWQ

Printed in Oreat Bntain. All rights reserved.0273-1223195 $9'50 +0-00

NUTRITION, ANIMAL PRODUCTION ANDTHE ENVIRONMENT

A. Rerat* and S. J. Kaushik**

• Centre de Recherches de Jouy, INRA, 78350 Jouy-en-Josas. France•• Laboratoire de Nutrition des Poissons. Unite Mute INRA-IFREMER.Station d'Hydrobio!ogie. INRA. 643/0 Saint Pee-sur-Nivelle. France

ABSTRACT

Wi!b increasing demographic grow!b, !bere will be an ever increasing demand for greater food productionover !be turn of this century. Seen from today's productivist point of view, this is not too difficult a challengeto meet. Besides socio-economic and geopolitical considerations, it is now of the utmost importance toconsider any such increase in food production from a global environmental perspective. Man-made changesto the environment are numerous, some perhaps irredeemable. The essential human activities of agriculture,animal production and fisheries also affect !be environment and some quantitative data are available on sucbimpacts.

Eacb progress in increasing agricultural resources (reclaiming new land areas for agriculture, increase in landproductivity, intensification of animal production etc.,) is not without disadvantages (deforestation, pollutionof underground water !brougb different contaminants). Imensification of land animal production, facilitatedalso by progress in biotechnological methods leads to increased contamination of the natural food chain andto the concentration of effluents. Aquatic production, currently undergoing tremendous progress, is alsofacing several sucb dangers: over-exploitation of natural resources; slow disappearance of natural breedinggrounds; increased pollution of water througb industrial, agricultural and aquacultural activities. Every suchmenace to the future of food production bas its solution. Even !be applIcation of already available knowledgecan prevent further deterioration of our land, air and aquatic environment for sustained production. But, localsocioeconomic pressures and lack of concern or education often prevent us from obtaining !be ideal balancebetween food production and environment.

KEYWORDS

Global food production; environment; nutrition.

INTRODUCTION

The world food production is currently capable of supporting all the requirements of humans. Foodproduction has been increasing faster than the world population over the last ten years (24 vs 20%), thanksto efforts in several fields. The per capita food energy intake has increased by a world average of 12% from1965 to 1985 (FAO, 1988). The average increase recorded in developing countries (19%) conceals widelydisparate situations, since the increase only amounted to 4% in Mrica, and the daily per capita intakeactually decreased between 1975 and 1985 in some sub-Saharan countries. The most basic requirements (8MJ) were not met in 1989 in nine developing countries, totalling 196 million inhabitants. The daily 10.5 MJlimit was exceeded, however, in 35 developing countries, totalling 1.88 billion inhabitants. It should bestressed that despite improvements, almost one billion people out of the current 5.5 billion populating the

Page 2: Nutrition, animal production and the environment

2 A. RERAT and S. J. KAUSHIK

earth live in dire poverty and cannot get sufficient food. Tens of millions more have to put up with natural orman-made disasters which deny them access to basic food.

Today's challenge is that changes in food production over the next decades must cope with a populationincrease and also smooth out current disparities. Demographic forecasts expect the world population toincrease on average 1.4 to 1.8% annually and to reach over 7 billion people in the year 2010 (Alexandratos.19S9; World Resources. 1992). The food demand will therefore increase by 36% over the next twenty years.This value must be matched by food production. allowing for distribution problems, if the status quo is to bemaintained. or exceeded, and the food shortage of the poorer countries is to be reduced.

The ir.teractions between nutrition, food and the environment may be analysed from two angles. On the onehand, an increase in the world population requires an increase in food production with which theenvironment will somehow have to cope. On the other hand, demographic pressure has a direct impact onthe air. land and water environments which changes the constraints on agricultural and aquatic ecosystems.This present paper will deal mainly with the cascade of reactions between demography. nutrition, foodproduction and the environment (Fig. I).

t Fllh _I~Ich

OVerfllhlngpollullon

FoOd---------=c

Demography

Nu~n !UrbanJzatJonI IIFood technology J- Incom. - I AnImal productIon IWall..

(+pAM. productJon

_AlIb.. landl_I/O.'o,.....llonIncr.... IIn1glllon

Ylald II Peellcld..-1ncrHM I Fertlllur.

lWeIif'

~ AnImal IISubclinical-/p"ro'duClJon dl......IW..le.

Figure I. Interactions between demography, food production, nutrition and the environment

One can distinguish two types of demographic constraints. Those of the ftrst type tend to be socioeconomicand are related to urbanization and changes in income which result in new patterns of consumption. Those ofthe second type are related to the increase in the volume of demand and correspond to the necessity offinding new resources.

CURRENT PROBLEMS DUE TO URBANIZATION AND LIVINGSTANDARDS

Population increases are usually accompanied by a population transfer from rural to urban areas. It is thusexpected that the world urban population will grow from 37% in 1970 to 52% in 2010. Population growthand urbanization will also be accompanied by changes in income. These two factors have a major impact onconsuming patterns and on food technology. and consequently on the environment

How do changes in living standards affect patterns of consumption? An increase in income has differenteffecl~ according to the economic situation of the recipients. If the recipients are very poor, the demand forstaple foods such as root~ and cereals soars, but if they are rich the demand shifts towards animal productsand sugar. The energy consumed in developed countries is divided into 2/3 plant products and 1/3 animalproducts. It seems that the percentage of animal products in these countries has reached a maximum. Some

Page 3: Nutrition, animal production and the environment

Nutrition. animal production and the environment 3

counuies (Eastern Europe. fonner Soviet Union) are quickly shifting towards this pattern whilst developingcounuies with a low income rely on cereals. roots and tubers for food, with an increase since 1970 (FAO,1987).

Table I. Protein and energy conversion efficiencies in different animals under whole fann situations

Dairy herdBeef cattleSheep flockPig herdBroilersEgg layers

Gross Energy (%)124.51.7

17to11

Protein (%)2563

122018

Salmonids > 30 > 30Data for land production from Holmes (1970) and for fish from Cho and Kaushik(1985).

Table 2. Food intake needs for maximum growth as multiples of maintenance needs

Dairy cow

Steers

PigFowl

Body weight (BW)(kg)550550300

50I

Productionper day

13 kg milk30 kg milk

0.4 kg0.7 kg1.0 kg

0.75 kg0.027 kg

ntimesmaintenance

24

1.41.72

2.31.5

Salmonids 0.1-1 1·2% BW 4-6Values for higher animals from Maynard et al. (1979) and those for fish calculatedfrom literature data.

As a result, the consumption of cereals by animals is growing rapidly in countries whose income isincreasing. It is expected that the use of cereals in animal feed in developing counuies will increase from15% in 1980 to 24% in 2000. This percentage is much higher in developed countries (around 65%) and hashardly changed at all since 1960. This tendency places a very heavy burden on changes in the world foodproduction. without being strictly necessary for satisfying the nuuitional requirements of humans. Thesignificance of animal products in the human diet should. nevenheless, cenainly not be dismissed. Animalproducts provide an appropriate balance of proteins in a small volume as well as very easily assimilatedminerals. vitamins and trace elements, the most conspicuous example of which is haem iron. However. theirconuibution relative to requirements is excessive in many developed countries and could be significantlyreduced. On the other hand. it is obvious that the conuibution of animal products should be greatly increasedin most developing countries, where they are insufficient. The shift towards consuming animal products isexpensive since the conversion of plant products by animals is a relatively inefficient process. Holmes(1970) reponed that the feed efficiency ratio under normal husbandry conditions, i.e. the percentage ofenergy in edible products obtained by the animal relative to that in the ingested food, is 4.5% for beef. 12%for milk and 17% for pork (Table 1). The ratio of proteins in products to ingested proteins varies from 6%for beef to 23% for milk. Resuicting our attention to monogasuic animals. which consume a balanced diet offeeds which could well be directly consumed by humans, the efficiency of protein deposition is less than20% in poultry (Holmes. 1970) and between 18 and 20% in pigs (Dourmad and Henry, personalcommunication). It should be emphasized that the production of fish by aquaculture is far more efficientthan any other form of animal production. In salmonids. for example. 30 to 40% of the crude energy intakeand 20 to 25% of the orotein intake are present in the fmal food. This is due to the fact that. bv comoarison

Page 4: Nutrition, animal production and the environment

4 A. RERAT and S. J. KAUSHIK

10.5 11510.0 10211 272.1 237.9 504.6 92~8 ~

58.5 35012.5 28033.4 1100100.3 420

with other animals. their maintenance needs are low so that more of feed eaten is available for growth (Table2).

In any event, a consequence of the low conversion efficiency of animals is that plant crops make moreefficient use of arable land when used to produce primary food for humans. than does any form of animalexcept some types of aquaculture (Table 3). When considering the production per unit area (as kg productionper hal, a notion which is not common in intensive culture of salmonids. but valid in the pond culturesystems, aquaculture is highly flexible (Table 4) and is currently practised as such in Asia and Africa. Theproduction can vary from 300 kg/ha with very little input to almost 500 t/ha with the full intensive systems.Even without having to go for intensive culture, extensive aquatic production appears to be an efficient wayof gcotting most (in terms of animal proteins) out of low inputs. Except for aquaculture. animal production isthus extremely costly. The consequence is that in developed countries. where animal products are consumedin large amounts. humans consume a 3-4 fold greater per capita cereal equivalent (I tlyear) than indeveloping countries (250 to 300 kg/year). where the consumption of plant products predominates (Leveille.1975).

Table 3. Annual yield from farm animals, crops and from fish

Energy (MJxIo-3/ha) Protein (kg/ha)Dairy cowsDairy + beef cattleBeef cattleSheepPigsBroilersEggsWheatPeasCabbagePotatoesFish (tilapia, carp)Extensive 1.5 - 8.4 45 - 260Semi-intensive 8.4 - 52.3 260 - 1600Intensive 41.8 - 230 1250 - 7000Data for land production from Holmes (1970). Data for fish recalculated fromHepher (1988) and Lovell (1988).

Table 4. Flexibility of aquaculture production

Culture systemExtensive pondsSemi-intensive ponds

Intensive ponds

Intensive cagesIntegrated

Major inputsnone to some manureInorganic fertilizers,

manure.agricultural byproducts

Supplemental.complete dietscomplete diets

cattle. pig, poultrydroppings

Production (kg/ha)280 - 1700

1600 - 10 000

8 000 • 450 000

300 000 - 55000020 - 7400

Recalculated from Lovell (1988) and Hepher (1988).

Although the cost of animal production is high because of its low efficiency, animal production will tend toincrease globally over the next few years, especially in developing countries. Animal production willtherefore intensify. concentrate and specialise. More plant products will be required and the environmentwill suffer as a result

Page 5: Nutrition, animal production and the environment

Nutrition. animal production and the environment

WORLD FOOD PRODUCTION AND ENVIRONMENTALCONSEQUENCES

s

Data on the production of the major food resources from 1987 to 1991 (Table 5) indicate that, worldwide.some groups of products have increased faster than the world population (oilseeds. pulses. sugar. meat andeggs) and others more slowly (vegetables, fruit, milk, roots. and tubers). Nevertheless, when only developingcountries are considered. the production of every agricultural product increased faster than the population ofthese countries except for the production of roots. tubers and vegetables. The imbalance between developingcountries and the rest of the world should be stressed since these countries represent 76% of the totalpopulation whereas their share in world production varies from 30% (milk) to 68% (roots and tubers). Theseare the countries where the largest production increases are required.

Table 5. Changes in plant and animal production (kt3) in developing countries between 1987 and 1991

World total Developing countries1987 1991 Change (%) 1987 1991 Change (%) % total

1991Cereals 1788419 1883888 5.3 932II9 1041962 II.8 55.3Roots 534737 574644 1.0 363371 393892 8.4 68.5Pulses 54837 59902 9.2 34345 40029 16.5 66.8Vegetables 434523 452336 5.0 282961 297941 5.3 65.9Fruits 335433 348140 3.7 209145 230130 10.0 66.1Nuts 4185 4322 3.3 2141 2467 15.2 57.1Oilcakes 136894 148055 8.1 68650 77458 12.8 52.3Oils 67726 76603 13.1 41781 49720 19.0 64.9Sugar 101928 II2224 10.1 58346 69867 19.7 62.3

Meat 162615 178830 10.0 61797 75196 21.7 42.0Milk 516130 528057 2.3 137939 158514 14.9 30.0Eggs 32560 35375 8.6 13339 16644 24.8 47.0

Population (x 106) 5026 5389 7.2 3799 4131 10.9 76.6Drawn from FAO (1992)

The increase in food resources over the last decades has occurred because of improvements in every sector(plant production. animal production and fisheries). due to an increase in the number and size of productionunits and surface areas accompanied by an increase in their productivity.

Optimizing the production of plant foods and feeds

According to Alexandratos (1989). the increase in plant production in developing countries over the nextyears will be obtained as follows: two thirds by improving yields (increasing by 1.6% annually or by 30%from 1982 to 2000); and about one fifth by extending arable lands (increasing by 0.6% annually) and 15%by intensifying cropping (increasing from 78% to 84% over 20 years). The distribution between thesepatterns of increase will of course vary to a great extent according to the geographic location.

Increasing the area allocated to agriculture. Allocating more land to agriculture depends on balancing theexploitation of the agro-ecosystems. reclaiming land areas with a cropping potential and reducing sterileland use such as for housing, infrastructure and industry. In 1985. the total arable land area in both rainy andirrigated areas added up to some 1470 million hectares. 53% of it in developing countries (FAD. 1988). Thisrepresents an increase of 100 million ha since 1965 (the equivalent of 3/4 of the crop land area of Europe)corresponding to an average annual increase of 0.5% over twenty years. However. the latter growth ratetended to decline over the last few years. and the above value hides a broad diversity of situations(Alexandratos. 1989). There is an excess of crop land in some regions (Europe. North America). in which

Page 6: Nutrition, animal production and the environment

6 A. RERAT and S. J. KAUSHIK

cultivated areas are stabilising or on the decline. There is still considerable scope for expanding until 2000 indeveloping countries since reserves add up to 150% of currently exploited land. However, these reserves areconcentrated in a few countries such as Brazil and Zaire, and are made up of poor quality soils. Moreover,some of these reserves are also located in areas where rainfall is irregular. Reserves are almost non-existentin the Middle East and in some Asian countries such as India where all the arable land is already fullyexploited. Whatever the case, it is estimated that developing countries will require 80-100 million ha of extracrop land by the year 2000.

Most of the world's increase in crop land (+ 2.2%) has been obtained at the expense offorests (- 1.8%) overthe last decade and this will continue. There are currently 4.1 billion ha of forests and wooded areas, 2.2billion of them in developing countries. Tropical forests cover 1.8 billion ha. Forest areas are stable orslightly on the increase in developed countries but they are continually decreasing in developing countries. Itis estimated that the deforestation rate in the tropics has increased from 11.5 million halyear in 1980 to 17million halyear in 1990 with only little reforestation going on (1.5 million halyear). Forests are exploitedmainly for fuelwood and timber, which also makes new land available. They should be exploited with muchcare and a good deal of common sense because of their importance in regulating the water, carbon andoxygen cycles and in preserving biodiversity. Deforestation can cause problems such as water and windinduced erosion, impoverished wildlife, desert formation and, last but not the least, disorder in mountaincatchment areas, which lead to alternating floods and droughts in coastal regions and to excessivesedimentation in natural and artificial reservoirs.

Another possible way of increasing the surface area available to agriculture is by reclaiming land which isnot used because it is too wet or too dry. There is tremendous scope for irrigating arid and semi-arid areas.Irrigated areas almost tripled from 1950 to 1985, by which time they covered 230 millions ha, 165 million ofwhich lay in developing countries (FAD, 1992). Irrigated areas produced one third of the world's food in19115 whilst amounting to only 15% of the crop land. Two thirds of the new crop land reclaimed by 2000will be irrigated, by which time irrigation will cover 320 million ha.

Land productivity. Productivity increased over recent decades by enhancing the amounts produced per unitof land area and per harvest (yield) as well as by increasing the number of harvests per year (croppingintensity). The growth in agricultural output over the next 15 years (+ 2.0% yearly) will be provided byincreasing the yields (63%) and the cropping intensity (15%). The methods that are and will be used arediverse and include genetic, chemical and nutritional methods and mechanisation. Genetic methods includecreating new plant species which are resistant to diseases and pests, and react well to irrigation andfertilisers. Chemical and nutritional methods include the use of fertilisers and pesticides and properlymanaging water resources. Some of these methods, especially the use of fertilisers and biocides, have adirect environmental impact.

- Chemical fertilisers. The use of chemical fertilisers to increase output has been well proven in developedcountries and is gradually making its way into developing countries also. The share of developing countriesin global fertiliser consumption has risen from 15% in the mid-sixties to over 40% in 1987. World fertiliserconsumption is constantly growing, from an average of 73 kg/ha in 1978 to 97 kg/ha in 1988. But, extensiveuse of chemical fertilisers can quickly lead to the leaching and seepage of highly soluble nutrients such asnitrate and potassium, and to the slower percolation of other less mobile substances such as cadmium,phosphates, agricultural biocides or soil disinfectants. All these substances eventually reach the groundwater where they accumulate. Leaching and seepage can occur in the rich and fertile parts of developedcountries, in dry irrigated areas where irrigation is poorly managed and fertilisers are misapplied, and insubmerged areas such as rice paddies which cover 10% of all the harvested land. Excessive amounts ofphosphate and nitrate from over-fertilised soils cause eutrophication in lakes and coastal areas whichsometimes has drastic results on aquatic ecosystems. Over-fertilization of the water leads to algal blooms,which deplete the oxygen required by other life forms. Dead algae sediment and decompose anaerobicallyinto methane, which contributes up to 15% of the greenhouse effect. The methane produced by rice paddiesmakes up 26% of the atmospheric methane. Chemical nitrogen fertilisers along with organic fertilisers also

Page 7: Nutrition, animal production and the environment

Nutrition. animal production and the envirol\lllent 7

cause atmospheric pollution by giving rise not only to ammonia. but also to dinitrogen oxide and nitrousoxide. The latter contribute up to 5% of the greenhouse effect and also deplete the stratospheric ozone layer.

- Biocides. The intensification of plant production has also boosted the outbreak of diseases and pests.Consequently. the use of toxic chemicals such as insecticides. herbicides and fungicides. has increased by anaverage of 4.5% per year for the world as a whole and by as much as 20% in some developing countries.

Biocides are highly effective when used properly but only a very small proportion of them (l %) actuallyreaches the target organism. The extensive use of biocides causes serious problems regarding the resistanceof pathogens and pests. the destruction of non-target species. and the accumulation of biocides in naturalenvironments and in food. Immoderate use of biocides contaminates aquatic resources. especiallycontinental waters. This is particularly obvious in developed countries but occurs in some developingcountries as well. Moreover, since some biocides are quite persistent. they are absorbed by plants andanimals and accumulate in their tissues, thus contaminating the food chain. Biocide concentrations in humanfoods can be excessive when poor agricultural practice is applied. such as harvesting prematurely afterapplying pesticides to crops, or catching fish in recently treated rice paddies.

The pesticide market will increase in developing countries over the next few years. although the amountsused per hectare will decrease because the new pesticides will be more efficient. On the other hand. adecrease is expected in developed countries where the older pesticides will gradually be abandoned. becauseresistant pests have made them inefficient and because of their noxious side effects, in favour of moreefficient and more specific pesticides.

An alternative to pesticides does exist for fighting phytopathogens. This consists of reinforcing theresistance of plants and destroying pathogenic organisms biologically. Resistant plants can be created byeither selection, hybridization or transgenosis. Insect pests can be made more infrequent or destroyed bymodifying their behaviour by using natural substances secreted by some plant and animal species or bymaking use of their natural enemies or predators. whether animals. plants or micro-organisms. Theprinciples involved in designing these various biological substitutes to insecticides are also applicable tofungicides, anti-bacterial agents. anti-viral agents and herbicides. It might therefore be possible to reduce theuse of chemical pesticides over the next decades. This task will be made easier if the available cropprotection methods. i.e. chemical. biological and genetic methods are combined into an integrated pestmanagement strategy by blending them into a production system designed for uncoupling the biology of thecrop from that of its aggressors. which can be obtained by playing on the timing and density of sowing. andon crop rotations.

Productivity of terrestrial anjmals

Actual and potential advanCt's. Animal production has progressed considerably over the last decades.particularly in developed countries. This has been achieved by perfecting and combining extremely powerfulproduction techniques that owe much to the spectacular boost in knowledge in the traditional biologicalfields of genetics. physiology, nutrition and husbandry. Strains and breeds of animals have been obtainedwhich are highly productive. have a very low disease rate because of more efficient prevention and cure andare well adapted to the hardships of confinement. For instance. the weight of feed required to make a piggrow by unit weight (feed/gain ratio =FGR) has been brought down from 4.50 in 1927 to 2.55 in 1988(Aumaitre and Courot, 1993). whilst the daily weight gain has increased from 580 g to almost 900 g. It canbe claimed that all available husbandry. environmental or genetic methods have contributed to this result(Fig. 2). Further progress can be achieved and the FGR in pigs may be further reduced to 2.2 by the end ofthe century. The amount of feed required to produce I kg of meat might be reduced from 7.8 kg. the bestresult so far. to less than 5 kg. The progress achieved in shortening the reproduction period is similar sincethe number of piglets produced each year by a sow has risen in France from 16 in 1970 to 22 in 1990(Leclercq and Legault, 1991). Aquaculture has similarly undergone tremendous progress since the FGR hasdropped from over 2.5 in the early sixties to less than 1.0 in the late eighties.

Page 8: Nutrition, animal production and the environment

8 A. RERAT and S. J. KAUSHIK

2.01917

1Wet feeding

1977

Grading selecllon for leannessI Reduction In weaning weight

1 Reduction in feed wastage

1

Feed additives

t Feed containing 11.71 MJ I kg

Balancing diets

IControl of feed Intake

11

Reduction III tnnal weight

Reduction in diseaseBreeding·growth rateI(reduction In maintenance) t 1

Housing and environmentStopping castration

3.6

2.4

4.0

3.2

2.8

Feedt :gain ratio

4.4

Figure 2. Factors affecting improvements in feed: Uve weight gain ratios during 1927-77 in pig production.

Recent techniques. derived from developments in cell and molecular biology. give rise to hopes that furtherprogress can yet be achieved. The fields of reproduction and genetics. which are inter-related. providesuperovulation and embryo transfer techniques. Added to artificial insemination. these techniques can helppropagate the genetic progress achieved by the traditional breeding programmes and the more recentmarker-assisted selection techniques. Progress in the field of animal pathology is also noteworthy: early andprecise diagnoses are possible. thanks to new reagents (ELISA. monoclonal antibodies. molecularhybridization); efficiency and coverage of prevention are extended by improvements in the production ofconventional vaccines and the design of new ones; cures are more active (new antibiotics. monoclonalantibodies). Improved nutrition has been achieved by applying both basic nutritional principles as well as byusing biotechnology: an increase in the quality of feeds (better balance between nutrients. absence of antinutritional factors) due to advances in plant production; increased efficiency of the diets by proper aminoacid supplementation and by the use of proper additives. new antibiotics and probiotics. and enzymes(xylana.'lCs. glucanases. cellulases. phytases) obtained from micro-organisms. For ruminants. the feedingvalue of silage can be increased (by inoculation or by adding enzymes) and engineering the ruminalmicroflora may also be feasible. Improvements that may be expected from the physiology of growth and oflactation include the better understanding of the use of growth factors. anabolic and partitioning agents.responsible for the distribution of nutrients in the tissues. Somatotropin and to a lesser extent J3-agonistsappear to hold some scope for improving the feed efficiency with which meat animals destined for slaughterproduce lean carcasses or for increasing the lactation yield of dairy cows. However. until fU1Tl evidence isavailable that they induce no side effects either on the animal or on the human consumer. the widespread useof such agent.~ are not to be encouraged. Besides. from a global perspective. such practices might lead tofurther disparities between developed and developing countries where the conventional methods have notyet been fully applied. Similarly. the creation of transgenic animals opens up very bright prospects in each ofthese fields. but is not yet fully under control nor thoroughly understood.

Genetic improvement.~ of the animals on the one hand. and improvements in husbandry techniques. feedingand the prevention of diseases on the other. have increased the efficiency and profitability of animalproduction. thereby putting it within the reach of more producers. The improvements in the efficiency of theanimal. both achieved and potential. have led to a significant boost in animal production in the developedcountries since the second world war. Developing countries have followed the same trend more recently asclearly indicated by changes in animal populations (Table 6). The most spectacular increase world-widefrom 1979 to 1989 was that of poultry production (44%). Production of other species has also increased

Page 9: Nutrition, animal production and the environment

Nutrition. animal production and the environment 9

noticeably: sheep and goats (14%) and pigs (9%). whereas that of cattle has increased only slightly (5%).The increase was much larger in developing countries as a whole: 71 % for poultry, 16% for sheep and goats,13% for pigs and 10% for cattle. Although the animal production in developing countries is catching up withthat of developed countries, the per capita production comes nowhere near it The production of developingcountries represents only from 59% (poultry and pigs) to 68-71% (sheep. goats. cattle) of the worldproduction whereas, their population currently represents over 76% of the world population. Animalpopulations cannot increase indefinitely because of the limited pasture capacity available to polygastricanimals in some countries and the insufficiency of concentrated feeds (cereals. cakes) for which the humanconsumer has a higher priority than monogastric animals. According to the FAO (Alexandratos. 1989) themeat production in developing countries may increase annually between 1984 and 2000 by 2.7% (cattle) to4.9% (poultry). pigs and sheep coming somewhere in between (3.3%); increase in milk production mayreach 3.1 %. This increase will be provided by an increase in the livestock populations (20%), by an increasein the efficiency of the animals (46%, which provides a higher amount of proteins to the consumer at a lowercost) and by improvements in husbandry conditions (sanitary conditions. feeding, 34%). These changes inlivestock populations and in the efficiency of husbandry will only be obtained by intensification, whichusually takes the form of specialisation and concentration. These changes also affect the environment

Table 6. Changes in livestock numbers between 1979 and 1989

Horses Cattle Camels Sheep Poultry Pigsand and and

donker buffalos goats(x 10 ) (x 1(3) (x 1(3) (x 1(3) (x 106) (x 1(3)

World total- 1979 111151 1219756 138854 1553333 7728 778787- 1989 119185 1277345 156982 1768406 11161 846976- change (1989 - 1979) 7.2 4.7 13.0 13.8 44.4 8.7

Developing countries- 1979 91383 793646 137813 1015059 38B 443925- 1989 100294 875194 155911 1181714 6518 500223- change (1989 - 1979) 9.7 10.3 13.1 16.4 71.0 12.7

- % World (1989) 84.1 68.5 99.3 66.8 58.4 59.1(Drawn from World Resources. 1992)

Possible consequences of the production of terrestrial animals on the environment:

Overxrazinx. Overgrazing, excessive concentrations of polygastric animals on pastures. weakens the plantcover and makes the soil vulnerable to water and wind induced erosion. The soil is compacted by trampling,thereby reducing its ability to hold water. Livestock eat saplings in forests. hindering regeneration; forestsare gradually turned into maquis or into savannah in areas with a Mediterranean climate. or into heath landin temperate areas. In semi-arid areas. the plant cover becomes scarce and gives way to wide barren spaceswhich are quickly taken over by sand dunes. Currently. 679 million ha are overgrazed. adding up to 35% ofall the degraded plant cover and 21.5% of the permanent pastures. Some areas are particularly affected byovergrazing which is responsible for 80% of the degraded land in Australia and 49% in Africa.

Intensification of animal production and human health. Increased livestock populations and theintensification of husbandry can affect Man's health in several ways. On a regional or local scale, livestockcan act as vectors to parasitic. microbial or viral diseases and an increase of their presence can have eitherbeneficial or adverse effects. Livestock occasionally protect humans from mosquitoes if the range lands orpermanent stallings are located between the mosquito breeding sites and the human dwellings. Usually.however. livestock act as a reservoir for parasites and viruses. amplify the corresponding diseases and makeit harder to eradicate them. Livestock provide the resources that insect populations require for developmentMIl JI.""

Page 10: Nutrition, animal production and the environment

10 A. RERAT and S. J. KAUSHIK

thereby enabling them to spread malaria (mosquitoes) and sleeping sickness (tsetse fly). Schistosomiasis isalso endemic in Asia because of livestock. Pig farming in Asia greatly amplifies the virus which causesJapanese B encephalitis, which is normally only transmitted on a small scale by wild animals.

The intensification of animal production in Europe and North America just after the second World Warmade it necessary to import ever more feed from tropical and subtropical countries. These feeds, the bulk ofwhich were plant products (palm nut, soybean) although animal products were also present (fish, blood...),are often contaminated by pathogenic micro-organisms such as salmonella. These feeds are a major sourceof animal diseases and a source of asymptomatic earners. The latter contaminate the environment byconstantly dispersing pathogens with their faeces and contaminate the whole food chain when they areslaughtered. Although there is a tendency for the initial source of contamination to disappear because of theprocesses used in the feed industry (especially pelleting), the widespread presence of infectious agents in theenvironment and amongst various animal vectors (insects, birds. rodents) has become the main reason whythese infections persist.

Rt'sidut's of vt'tt'rinary drugs and feed additives. Animal diseases decrease productivity. Livestock aretherefore treated with active substances (vaccines. additives) for the prevention and cure (drugs) of diseases.Moreover. various hormones and drugs can help improve the growth performance, body composition andproduction efficiency of animals destined for slaughter (Roche and O'Callaghan, 1984). Natural andsynthetic steroid hormones have been widely used in ruminants because of their ability to stimulate proteinanabolism. They are highly effective in calves. have a marked effect on culled cows and are not veryeffective in bulls. Androgens have been used successfully in heifers and oestrogens in castrated animals.These substances have now been banned in the European Union because consumers are worried about theputative long-term dangers associated with consuming the meat of the treated animals. Paradoxically, theyare allowed in North and South America, which creates a delicate international trade situation because oftheir effectiveness. Steroids are not used in other species because their effectiveness is uncertain.

It has recently been verified that sympathomimetic agents can alter the composition of different tissues inthe organism and therefore provide a means of decreasing the fatness of carcasses (Buttery et at., 1986).Although their effectiveness in doing this is very clear. their influence on the growth rate and feed efficiencyratio is debatable. Moreover, the half life of these agents in the tissues is long and they should not be usedfor some time before slaughtering. thereby limiting much of the benefits that can be gained from them.

Somatotropins, heterologous or homologous. are currently the focus of much attention because they improvethe body composition of animals destined for slaughter and milk production (Armstrong, 1987).Interestingly for meat production. somatotropin affects the body composition much more than it affects thegrowth rate. Fatness decreases. These beneficial effects have been recorded mainly in pigs and sheep but noevidence is available for cattle. Pigs are affected in a very spectacular way (Van der Wal t't at., 1989); thedaily weight increase can be brought up by 10 to 20% and most of the extra weight is lean tissues since theirdeposition rate increases by 30% whereas that of fat decreases by 10%; the feed efficiency ratio is also muchimproved but this varies more widely. It is believed that the same physiological and metabolic mechanismsare involved as in the genetically selected. best animals. But. it is claimed that somatotropin improves thedesired performance factors in pigs by the equivalent of over 10 years of selecting for these characteristics.However, as mentioned earlier, the question remains as to the inocuity of such agents on animal and humanhealth.

Antibacterial agents are used in veterinary medicine or as feed additives so as to increase the effectiveness ofthe diets. When they are used inappropriately for veterinary treatments. they may end up in the animalprodUCl~. In the USA. concentrations of these residues below 1 ppm (1 mg/kg fresh meat or milk) are quitefrequently found in milk (50%, New York City) and less commonly in meat (5% of carcasses). The agentsresponsible are tetracyclines. sulfamides or aminosides. The use of antibiotics for improving the feedefficiency of livestock is strictly regulated, as is that of any growth promoter. The antibiotics are differentfrom those for therapeutic use and the recommended doses are 100 times smaller. No residue can bedetected in the tissues and organs under these conditions. In fact. residues are only present as a result of

Page 11: Nutrition, animal production and the environment

Nutrition, animal production and the environment 11

therapeutic use. One may wonder whether residues of therapeutic doses of antibiotics used in livestock are athreat to human health because they may select for a resistant microflora. There seems to be no risk of thishappening now because the antibiotic residues at the observed concentrations have no measurable incidenceon human digestive flora (Corpet, 1992).

Production of wastes and the environment. The intensification of indoor animal production creates largelocal amounts of effluent formed by slurries and manure. Effluent production per unit area varies greatlyaccording to the density of livestock in each country. Within the European Union. the Netherlands producefive times as much effluent per unit area as does France and 19 times as much as Greece. Largeconcentrations of animals pollute the atmosphere. land and water to various extents. Organic wastecontaining large amounts of nitrogen compounds, phosphate and potassium and other metals (Cu. ZIt, Cd.heavy metals) is spread as a fertiliser on agricultural land. causing a number of ecological disturbances. Partof the contents do contribute to plant nutrition but a large amount also accumulates in the top layers of thesoil, percolates to the ground water or is washed away with the runoff. The ground water and surface waterof intensive livestock production areas are extensively polluted because of manure spreading. For example.the nitrate concentration in the deep aquifers of some sandy parts of the Netherlands has increased from 10mgll in 1967 to 50 mgll in 1987.

A... mentioned above (Land productivity), one of the consequences of the nitrate overload and moreimportantly of the phosphorus overload in the surface water is eutrophication. The use of copper sulphate asa growth stimulant in pigs in recent years is an interesting example. Excess copper in spread manure has astrong negative impact on the development of plant roots in species such as maize by creating a secondaryphosphorus deficiency. Since most plants cannot tolerate an annual copper input greater than 50 glha. it isobvious that copper input through manure spreading in areas of intensive livestock farming is excessive. Insome part.... of the Netherlands for instance, 250 to 2500 g copperlha are spread annually (de Haan. 1991).leading to stringent regulations which limit the copper levels input in the diets of pigs.

Stables and feedlots release very large amounts of ammonia locally. This gas is also released into theatmosphere by the manure spread on cultivated land. The total amount of ammonia released from all sourcescan be very large. In addition, fermentation in the digestive tract of ruminants releases methane at a currentlyestimated rate of 70-80 millions tonnes per year for the whole world. This methane constitutes 20-30% ofthe total world methane output. methane also being produced by the decomposition of organic matter inwetlands and by the burning of organic matter. Methane produced by animals thus contributes to about 5%of the greenhouse effect

Wastes from intensive husbandry systems can. however. be reduced. even if the production of livestock is toincreao;e. Nitrogen waste can be managed by (i) tailoring the protein content of the diet accurately to therequirement of the animal, (ii) balancing the proteins ingested with supplementary amino acids and (iii)judicious use of hormones and related substances that regulate the nitrogen metabolism. such assomatotropin. Phosphorus. because it is the limiting nutrient in ecosystems. may cause even greatereutrophication problems than does nitrogen. It can be managed by enhancing the utilisation of the organicphosphorus input with phytase which markedly reduces the amount of inorganic phosphorus required andhence its excretion. It is becoming increasingly evident that nitrogen and phosphorus excreted bymonogastric or polygastric animals could be reduced by 25 to 50% (Jongbloed and Lenis, 1991; Korevaar,1991; Sweeten, 1992) by proper nutritional and feeding practices.

Re~ional specialisation of a~ricultural production: consequences for recycling animal and plant wastes.The intensification of agriculture USUally leads to a separation between animal and plant production. This iscurrently the cao;e in developed countries. The shortage of animal manure in areas where plant productiondominates has increased the demand for mineral fertilisers. which, if over-used. as they often are. causevarious types of pollution. This can be partly overcome by recycling plant residues, which provide nutrientsto plants and are beneficial for the soil structure and resistance to erosion. This is also a very useful way ofdisposing of plant residues. Conversely, intensive animal production areas import much of the feed theyrequire from other agricultural areas. before using them with the relatively low feed efficiency (15 to 20%)

Page 12: Nutrition, animal production and the environment

12 A. RERATand S. J. KAUSHIK

underlined previously. Therefore, the production of slurries and manure greatly exceeds what could beincorporated into the ground, with the adverse effects mentioned above. This situation is found in theNetherlands and in some French regions such as Brittany. Surplus manure should therefore be stored andexported where it could be used more rationally in a better integrated system requiring less mineraifertilisers.

SOIL FERnUZAnON IN DEVELOPING ANDDEVELOPED COUNTRIES COMPARED

I p,...nt status I

QOe~v!!.!e!JJ1O;ml!!i£.2Y.IJ1!:i:u (2)

~......(++)In u c: nt c:hem c:al f rtlllz:.rs

Plants

~F d Ruffs

!I++IAnimals

!EIlc:. Imanure

1++Ir-

Chem c:al,.rtiliz.,..

I~I

prntl

F..tstUffs

1+)

(++I! I (++)

F••d Itu"S

! (+,

Ii)Ch mlc:1,..1il I''''

An m.'111+1

Mlnure

(tl

rm.nu....

!(+)

F.w.r c:h.m c: I'ertiliurs

I (+)

8011 NutrienIs In adeqU* ....... nWient baIanu ]~ fOr ,.".. fOr pI8nts~------

Figure 3. Present status and desirable position in soil fertilization in developing and developed countries.

Page 13: Nutrition, animal production and the environment

Nutrition. animal production and the environment 13

The input of fertilisers into crop production and of feed into animal production in developed countries farexceeds the amount of plant and animal products produced but the converse is usually true in developingcountries (Fig. 3). There is an excess of plant products relative to nutrient supplies in the soil in developingcountries, where the use of chemical fertilisers is limited by economic factors. This gradually exhausts thesoil, degrades its physical properties and upsets the water balance. Improvements can be obtained bysimultaneously returning plant residues to the ground, using just sufficient amounts of fertiliser anddeveloping livestock. Livestock production in developing countries has the dual advantage of avoiding theexport of local plant products to countries or areas where they will be used as feed for animals (that arealready overproducing manure) and of recycling animal residues locally.

Exploitation and management of aQuatic reSQurces

Fisheries and Aquaculture. World fish production increased over the last twenty years from 65 milliontQnnes in 1970 to nearly 100 million in 1989, followed by a small drop in the following years (97 milliontonnes 1991). Most of this fish is produced by marine fisheries (82%). Projections expect the demand forfish to increase by a further 20 milliQn tonnes Qver the next twenty years, mainly frQm developing countries.Can such a demand be satisfied? Changes affecting sea fisheries have been well analysed (FAD, 1992). Fishresources are over-exploited in 4 Qf the 17 FAD fishing areas: Far Eastern seas from India to Australia andJapan, the Mediterranean and the Pacific coast of South America. Increasing catches in these areas willdeplete the target species and could upset balances in the marine fauna. Dver-exploitation of krill is a threatto some species of whales and sea birds. Catches have decreased for some reason Qr another in 9 Qf thefishing areas (decrease in the anchQvy pQpulatiQns of Peruvian waters used to produce fishmeal for animalfeed; quotas in the North East Atlantic; decrease in available stocks off Japan due to natural fluctuations inproductivity and to over-explQitatiQn). In SQme areas, such as along the Atlantic CQast Qf North America,30% of the species are affected by over fishing leading to a decrease in the volume Qf catches with adecreased use Qf fish as animal feed. The propQrtion Qf fish cQnverted intQ fishmeal has decreased (40% in1970; 30% in 1985). The per capita fish consumptiQn has increased only slightly from 11.4 kg/year in 1978tQ 13 kg/year in 1988.

However, optimistic analyses (AlexandratQs, 1989) claim that the world can sustain an annual productiQn ofup to 120 million tonnes. AlthQugh demersal fish stocks are already fully exploited and stocks of manyspecies cannot be properly replenished because of over-exploitation, it is probably still possible to increasecatches of pelagic species, small schQoling species and deep water species. Aquaculture can also be furtherdeveloped on intensive commercial farms or more extensively in rural areas where it is traditionallypractised in ponds and irrigated areas. Finally, fishery resources can be better used by avoiding post-harvestlosses thanks to better storage methods or by reducing the amount of catch which is discarded.

Although marine and freshwater aquaculture only contribute 12% of the current overall fishery production,aquaculture certainly appears a promising resource; thus the production from aquaculture doubled between1984 and 1991 (from 6.7 to 12.7 million tonnes for cultured organisms) while increase of sea captures wasonly 9% (Table 7). Within this increase, feed-based aquaculture, that is finfISh and crustacean production,has benefited, whereas non-feed-based culture has remained low. With regard to bivalves (oysters, musselsand clams, etc.), the total production is currently estimated at more than 4 million tonnes and the areas undercultivation are mostly found in the northern hemisphere. This has been an age-old tradition in Europe and insome part.~ of Asia. Disparities also seem to appear with respect to finfish species themselves (Table 8). Carpculture (mainly in Asia) has seen a tremendous increase - similarly, the culture of salmonids in marinewaters (Atlantic as well as Pacific salmon) has increased from about 40,000 to 300,000 tonnes. If weconsider, now, the contribution of cultured fish - as an animal protein source - as food for humans, hereagain considerable disparities appear between areas (Table 9). But they also reflect, to a certain extent, theinfluence of long aquaculture/fIShing traditions in different parts of the world. Humans apparently continueto make the best out of what they have always done and with what is best available locally. The percentageof total fish intake coming from aquaculture is thus higher in Australasia (14%) than in North America (5%)or Mrica (0.3%). The Asian continent is the most deeply involved in aquaculture, since 85% of total worldfish culture come from Asia, and more precisely 75% from developing Asian countries.

Page 14: Nutrition, animal production and the environment

14 A. mAT and S. J. KAUSHIK

Table 7. World fishery production (Mt)

1984 1991Capture Culture Capture Culture

Fish and shellfishInland 6.1 3.9 7.5 7.7Brackishwater 1.8 0.7 1.9 1.3Marine 69.4 2.1 74.9 3.7Total 77.3 6.7 84.3 12.7

Feed-based aquacultureFinfish 4.4 8.7Crustaceans 0.2 0.8

Non-feed based cultureMolluscs 2.1 3.2Seaweeds 3.5 3.9

Source: FAD (1992)

Table 8. Growth of major finfish production (kt)

FreshwaterCyprinidsSalmonidsTilapiasSturgeonsCatfishes

MarineMilkfishSalmonids

AtlanticPacific

YellowtailBass / Breams

Source: FAD (1992)

1984

2880220190150130

310372710

17030

1991

6130320405410260

41029022070

19060

Table 9. Fish as human food: Per capita annual fish culture production, fish intake and coverage

Production Intake Coverage(kg) (kg) (%)

Asia and OceaniaEuropeN. AmericaS.AmericaAfrica

2.3 15.8 141~ 1~0 9Q8 1~6 51.6 18.0 90.03 10.5 0.3

Water quality management. All human activities affect water quality (Table 10). The relationships betweenfish resources and the environment are again multiple. On the one hand, environmental degradation hassome deleterious effects on fish production; on the other, fish capture and more particularly fish culture mayalso have some disadvantages for the environment. Aquatic resources are threatened by over-fishing,reduced access to spawning sites and pollution of aquatic ecosystems. River management, through dams andwater extraction, leads to barriers to the productivity of such mhu-atinjl species as salmon and eels. The

Page 15: Nutrition, animal production and the environment

Nulrilion, animal production and the environment IS

sensitivity of aquatic organisms to given pollutants is high. but also extremely variable making it difficult forobjective evaluation of the ill effects of pollutants (Day. 1992).

Table 10. Human activities that affect mariculture

From freshwater sources :Agriculture, domestic or industrialactivities

From marine I coastal sourcesTourism. shipping and biologicalactivities

Organic matter. bacteria, nutrient drainschemical, heavy metal. mineral andbiological pollutants

organic matter. bacterial. chemical.petrochemical pollutants. toxicphytoplankton

In the field of animal production. eutrophication is one of the most serious concerns which can. on a short•term basis. affect further development of aquaculture. The magnitude of the potential danger is illustrated bythe various situations found in different EEC countries (Table 11).

Table 11. The eutrophication problem in the EEC Countries

Natural Reservoirs. Estuarieslakes rivers and lagoons

irrigationsystems

Marinecoastalwaters

++++

++

+

+

+

+

++++++

+++

++++

BelgiumDenmarkFranceGermany (FRq)GreeceIrelandItalyLuxembourgThe Netherlands + ++United Kingdom ++ +++=identified problem, ++ =serious problems on a national scale.(from Vighi and Chiaudani. 1985)

Direct or indirect discharges of organic drain-offs or wastes from other human activities fmally end up in thesea. Thus, marine pollution has tended to increase over the last years. The major polluted areas are coastalzones, estuaries and closed seas which contain sediment, nitrogen and phosphorus derived lrom sewage anderosion. Phosphorus and nitrogen inputs into coastal zones have increased by 50 to 200% due to humanactivity. Excess nutrients enhance the development of algae. some of which are toxic to fish andinvertebrates, and lead to smothering of coral reefs. Excessive development of macro- and micro-algae.including dinoflagellates, causes red, brown and green algal blooms. Treating sewage reduces pollution. asin Singapore and Chesapeake Bay. but most of it still flows into the sea untreated. Sewage containspathogenic organisms such as the bacteria or viruses that induce typhoid fever. cholera and hepatitis. whichcan be contracted via nutrition or bathing. Toxic substances naturally produced by some dinoflagellates canbe concentrated in bivalve tissues that feed on dinoflagellates. Eating the shellfish can then cause poisoningresulting in diarrhoea and paralysis. Some tropical fish also consume dinoflagellates producing a toxin(ciguatoxin) and developing in sewage-contaminated water. Because ciguatoxin is heat-stable. both thesefish and their predators (groupers and snappers) can cause a disease in consumers. with cardiovascular anddigestive symptoms, called ciguatera which affects 5000 people annually.

Page 16: Nutrition, animal production and the environment

16 A. RERAT and S. J. KAUSHIK

Toxic chemical pollutants include heavy metals and synthetic organic compounds which are all accumulatedby marine organisms and concentrated in the tissues of predators. They can cause lesions in the fish andaccumulate in human consumers too. Organic compounds, such as PCB and DDT, are found in the wholeocean from the Arctic to the Antarctic. It is suspected that they reduce the resistance of marine mammals todiseases. Heavy metals are a major result of man's activity, especially mercury, cadmium, lead and tin. Someof these are particularly liable to accumulation in fish. Over a third of the daily mercury intake in developedcountries comes from fish, although fish is a very minor dietary component in these countries (2%). Heavymetals also accumulate in shellfish where their concentration depends on the amount discharged. Forinstance, the lead content in USA shellfish fell after lead was banned from petrol. The impact on humanhealth depends both on the concentration in seafood and on the amount of seafood consumed. Thepopulation most at risk are coastal dwellers and fishermen whose source of proteins is fish caught incontaminated areas. However, analyses and epidemiological surveys are insufficient to assess the long termeffects of low level contamination.

What are the disadvantages of fish culture for the environment? Aquaculture, like any other agricultural orindustrial activity, can lead to harmful effects on the environment. These harmful effects can be numerousand of different kinds: nutrient discharge, chemicals and antibiotics, use of plastics, escape of domesticated•genotypically modified (e.g. triploid) species into the natural environment. All of these different effectsmodify in one way or another the aquatic environment upon which aquaculture itself depends. Instances ofmas.~iveescapes from fish farms, such as Atlantic salmon on the north-west coast of the American continent,might affect biodiversity. Introduction of non-indigenous species for aquaculture (tilapia or carp to placeswhere they were not before) are known to affect survival and reproductive success of indigenous species.The increasingly widespread presence of intensive aquaculture under semi-natural conditions (floating cagesin estuaries and lakes, fry releases) can cause eutrophication, due to the increase in the amount of feed wasteand the production of excreta, and chemical pollution, because of the drugs used to prevent fish diseases.

While rural aquaculture can be beneficial for the environment by recycling organic waste (as is done inChina, for instance) and by controlling water-related human diseases such as malaria, filariasis and JapaneseB encephalitis, the increase in aquaculture is more and more due to increased intensification and to the useof supplementary or complementary feeds. The pivotal role of good nutrition must be underlined in bringingdown one of the possible ill effects of aquaculture: that is improving nutrient availability, absorption andretention to organisms, avoiding feed wash and so the introduction of nutrients into the very environmentwhich must be protected for the sustainable development of aquaculture. Examples may be taken from twodifferent aquaculture situations, one on salmonids and the other based on semi-intensive aquaculture ofcyprinids. Given that under current production levels, the amount of nitrogen and phosphorus lost per unitproduction of each of these groups of fish is fairly well known, Kaushik (1994) calculated that on a globalscale, even if the carp culture based on feeds is currently only 2% of the total, the phosphorus losses areapparently as high as those from the culture of rainbow trout. With increasing intensification, these figuresmight increase unless some attention is paid to improving feeding strategies and feed quality even under thesemi-intensive farming conditions prevailing in most developing countries.

Whether it is land animal production or aquaculture, the nutritional principles behind reducing effluentamount and modifying effluent composition are the same. The beneficial effects of somatrotropic factors(growth hormones) on improved protein utilisation, decreased N loss and higher lean body mass have alsobeen shown in fish, as in other animals (M~dale et al., 1988; Foster et al., 1991). But, even as in the case ofterrestrial animals, such progress would appear to be of limited value from different points of view:overproduction, consumer acceptance, etc. There are fortunately, a number of simple nutritional means fordecreasing the release of suspended matter, nitrogen or phosphorus losses of dietary origin and forimproving production (Table 12).

Page 17: Nutrition, animal production and the environment

Nuuition, animal production and the environment

Table 12. Basic nutritional principles behind the reduction of nutrient discharge into the environment

Reduction of suspended matter releaseoptimise feed intakedecreased feed lossimproved digestibility of feeds and feed ingredients

Reduction of nitrogenous losseschoice of proteins with ideal AA proftlesamino acid supplementation when necessaryoptimise protein-energy ratiouse of partitioning agents

Reduction of phosphorous lossesreduce dietary Pincrease P availabilityuse of phytases in diets with high phytate content

CONCLUSIONS

17

Of all human activities. the search for food is the most justifiable. But in order to maintain sustainedavailability of food for future generations of an ever increasing world population. food production practicesshould become more closely integrated with one another and with the natural environment Plant, animal oraquatic production are all intimately linked: the detrimental effects of poor management of one on others areonly too evident. In all production systems. there is clear evidence that the environmental impact due toinadequate nutritional practices can be diminished or limited. There is now a dire necessity to implementwhatever knowledge is available to improve and optimise nutrient I energy (fuel) utilisation at all stages offood production: terrestrial plants and animals. capture and culture of aquatic organisms. As water is both areceptacle of wastes and a vital source for all such production. the need for quality control of the aquaticenvironment is crucial for the future of human food resources.

The major conclusion of this analysis is that the world food production capacity will be able to cope with thepopulation increase over coming decades. provided that natural resources are properly managed. Whateverthe approach. be it traditional (yield increase. prevention of losses) or novel (biotechnological tools.increasing resistance to diseases). we are now fortunate to have reached a general consensus on theimportance of an "environmentally conscious" approach to all human activities. Although technologically Iscientifically sound solutions are available. problems often arise when they have to be applied globallybecause of local. frozen socio-economic situations.

Animal production must cease increasing in developed countries and should be fairly stimulated indeveloping countries whilst not reaching the excessive level it has attained in the developed world. Thisshould improve matters for the neediest of the local populations and. at the same time. balance the nutrientequilibrium of natural ecosystems in developing countries by reducing the export of plant products. and byrecycling part of the major nutrients (80% for nitrogen) through spreading manure.

The production of manure (especially nitrogen and phosphorus contents) can be greatly reduced by usinganimal production methods which enhance nutrient retention. However. in areas of intensive animalproduction. waste will continue to be produced at a greater rate than the land can absorb. Limited chemicalfertiliser inputs and recycled plant residues ought to be more common the world over. Moreover. the currentpolicy of specialising farming areas into cropping and livestock rearing needs a revision.

While chemical biocides were a cornerstone in developing food production during recent decades. they arealso causative agents increasing pollution and decreasing biodiversity. Their use should be restricted in thefuture by using more ecological and more specific techniques reinforcing the genetic capacity of plants and

Page 18: Nutrition, animal production and the environment

18 A. RERAT and S. J. KAUSHlK

animals to resist diseases. biological control, integrated pest management and "biopesticides". Progressachieved so far is encouraging.

Problems to which there are no immediate clear-cut answers include the emission of gases. acid rain.deforestation. desert formation and over-fishing. Although means of prevention are well known, they arehard to implement because the problems arise from the absolute necessity for some populations to find newresources in the form of new croplands, or to exploit to the utmost - usually beyond what is reasonable - theavailable land and marine resources. Over-exploitation of the oceans should be countered immediately lestresources will start to decline naturally leading to production shortages. Once again. regional over•exploitation clearly results from necessity so alternatives will be hard to fmd.

Anticipating a human tide around the tum of the century. it is crucial to realise that the resources of the earthare exhaustible and should be managed with the utmost wisdom and care if the interests of futuregenerations are to be safeguarded. The survival of agricultural and aquatic ecosystems depends heavily ontwo factors. The first of these is how the ecosystems are exploited for increasing production of food.clothing. medicine and fuel. The second factor is the multiplication of very diversified human activities.Everything possible should be done to help implement soundly the methods most suited to local ecosystemswhile including the powerful tools of biotechnology. Borders do not really matter when dealing with theenvironment and food production because interdependence between any country and its neighbours, both farand near. is very strong. The sustainability of agricultural and aquatic ecosystems. and hence of foodproduction. depends on how the particulars of each country are taken into account, leading to theimplementation of a world policy in which natural resources are exploited in an even fashion.

The authors thank John Philip Butler for help in translating parts of the original French manuscript intoEnglish.

REFERENCES

A1exandralos, N. (1989). L'agriculturl! mondialt!. Horizon 2000. Economica, Paris and FAD I Rome, 396p.Armstrong, D. C. (19117). The implications of biotechnology for livestock production. nutrition and health. Roche research prize

for Animal Nulrition. Hoffmann La Roche, Basel.Aumaitre, A. and Courot, M. (1993). Dbjectifs et activitts de la recherche porcine en Europe. 25~ joumoo Recherches Porcines en

France, Rechercbe-~veloppemenl, La nouvelle donne, INRNITP. Paris, pp 11-24.Buttery. J. P.• Lindsay. D. B. and Haynes, N. B. (1986). Control and Manipulation of Animol Growth. Bulterworths. London.

347p.Cho, C. Y. and Kaushik. S. J. (1985), Effects of protein inlake on metabolizable and net energy values of fish diets. In: Nutrition

and Fuding ofFish, C. B. Cowey. A. M. Mackie andJ. G. Bell (&Is.), Academic Press. London. 95-117.Cho. C. Y. and Kaushik, S. J. (1990). Nutritional energetics in fish: Energy and protein utilization in rainbow trout (Salmo

Rairdnl!ri). World Rev. Nutr. Dil!t.. 61,132-172.Corpel, D. E. (1992). Residus antibiotiques et microtlore digestive. Bull. Acad. Nail. Ml!d.• 176,475-484.Day. K. E. (1992). Assessment of the environmental hazards of pesticides to aquatic biota. In: Agriculturl! and watu quality. M.

H. Miller. J. E. Fitzgibbon, G. C. Fox. R. W. Gillham and H. R. Whiteney (&Is.). Univ. Guelph, Centre for Soil andWater Conservation. Guelph. Ontario. Canada, 91-116.

de Haan, F. A. M. (l99\). Livestock wastes and the environment. In: Livestock production towards the 21st century. Roche Symp.Animal Nulrition and Health, Rocbe, Basel, pp. 27-37.

F. A. D. Food and Agriculture Organization (1987). La cinquitml! I!nqutu mondiall! sur l'aliml!ntation. FAD, Rome, 75p.F. A. D. Food and Agriculture Organization (1988). World agricullurl! statiS/ics. FAD. Rome, 187p.F. A. D. Food and Agriculture Organization (1992). World production /99/. FAD. Rome, 265p.Foster. A. R.• Houlihan. D. F.• Gray. C., MMaie. F.• Fauconneau, B., Kaushik, S. J. and Le Bail. P. Y. (1991). The effects ofovine

growth hormone 01\ protein turnover in rainbow trout GI!II. Compo Endocrinol.• 82. 111-120.Hepher. B. ()988). Nutrition ofpondfishl!s. Cambridge Univ. Press, Cambridge. UK. 3118p.Holmes, W. (1970). Animals for food. Proc. Nutr. Soc., 29, 237-244.Jongbloed. A. W. and Lenis. N. P. (\99\). Effect of pig production systems on the environment 42nd Ann. Meeting EAAP,

Berlin. votl. 546-547.Kaushik. S. J. (1993). Recent trends in the development of high-energy diets for saImonids. In: Proc. 2nd Int. Fud Production

Con/.. G. Piva (Ed.). Casa Edit. Mattioli. Fidenza, Italy. 361-372.Kaushik. S. J. () 994). Nutrient requirements, supply and utilization in the context of carp culture. Aquacullurl!. 129. 225-241.KorevaaT. H. () 99 I). The rutrogen balance in intensive dairy farms. 4200 Ann. Meeting EAAP. Berlin. vol. I, 532-533.

Page 19: Nutrition, animal production and the environment

Nutrition. animal production and the environment 19

Leclercq. B. and Legault, C. (1991). Evolution pr6visible des fili~res et de leurs probl~mes chez les mOllogastriques. S6minaire sur1'Elevage. Theix. INRA. France. 28p.

LeveiU6, G. A. (1975). Issues in human nutritiOll and their probable impact on foods of animal origin. J. Anint. Sci•• 41. 723·731.Lovell. T. (1988). Nutrition and Feeding ofFish. Van Nostrand Reinhold, New York, 260pp.Maynard, L. A.• Loosli. J. K.• Hintz, H. F. and Warner. R. G. (1979). Animal nutrition. VII edition. McGraw Hill. New Yort,

602p.MMaie F.• Fauconneau B. and Kausbik S. J. (1988). Effect of GH administration on energy metabolism in rainbow trout. 10th

ESCPB conf. Energy transformations in cells and animals. lnnsbruck. AbstractRoche. J. F. and O·Callagan. D. (1984). Manipulation ofGrowth ofFarm Animals. Martinus Nijhof. The Hague.Sweeten. J. M. (1992). Livestock and poultry waste management: a national overreview. In: National Livestock. Poultry and

Aquaculture Waste Management. J. Blake. J. Donald and W. Magette (Eds.). Amer. Soc. Agric. Engg.• St Joseph, MI. 4•15.

van lIer WaI, P.• Nieuwbof. G. J. and Politiek. R. D. (1989). Biotechnology for the control of growth and product quality in swine.Implications and acceptability. Pudoc. Washington. 353pp.

Vighi. M. and Chiaudanl. G. (1985). The impact of agricultural loads on eutrophication in EEC surface waters. In: Environmentand Chemicals in Agriculture. F. P. W. Winteringham (Ed.). Elsevier Applied Science. London. 71·85.

World Resources. 1992-1993. Aguide to global environment. Towards sustainable development. (1992). Oxford University Press,Oxford. 385p.