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Kentucky Dairy Notes May 2017
To Keep or to Cull By: Karmella Dolecheck and Jeffrey Bewley
Sometimes choosing when to replace something is
easy. For example, a light bulb works equally as well on the day you first put it in and the minute before it stops working. When it stops working, it completely stops working and you know it is time to replace it. This is involuntary replacement; your only options are to go without light or to replace the light bulb.
Often times, choosing when to replace a dairy cow is more difficult. There are still times that involuntary culling is necessary. For example, if a cow dies, then the options are to go without a cow or to replace her. However, if a cow does not die, then she always still has some production potential. Therefore, the key to culling is determining at what point the cow’s production potential has dropped enough to warrant replacement. This type of culling is termed voluntary. Voluntary removal refers to cows that are removed from the herd in an unforced manner – it is completely up to the farmer to keep or cull her. Reasons for voluntary culling might include low production or bad temperament. Voluntary culling is a tool dairy farms can use to improve their overall herds (by keeping the best cows and replacing the worst), to keep the herd size from growing beyond capacity, and to maximize profits.
Which cows to voluntarily cull and at what point in time can quickly become complicated. The simplest way to think of voluntary culling is by comparing it to managing employees in an office environment. Each employee has their own office space. If one employee is not being productive enough to pay for that office space or if there is an employee that could increase profits more than the current employee, then the employee is replaced. Similarly, on a dairy farm, each cow has a stall. If that cow is not being productive enough to pay for that stall or if another cow could increase profits even further, the current cow should be replaced. In short, a cow should be culled when higher profits are expected from her replacement.
Mathematically, we can calculate the “optimal time of replacement” for a cow using a fairly straight-forward equation:
Optimal moment of replacement = the moment
when expected future profits from the current cow < expected future profits from a replacement cow
Unfortunately, calculating the individual pieces of this
equation is not easy. The expected future profits from the current cow depends on many things including the cow’s age, production, days in milk, reproductive status, previous and current diseases, etc. Combining all of these things not only for today but also for many years to come AND estimating the expected lifetime of the cow is difficult. On top of that, estimating the future profits and lifespan of her replacement makes the task twice as difficult. Here are some tips to help with on-farm culling decisions:
1. Know and keep in mind your target herd size.
Culling is the best strategy a farmer has to controlling herd size. Being aware of your current and target herd size dictates if, when, and how many cows to cull. When defining a target herd size, keep in mind limitations like housing, feed resources, and labor.
2. Be aware of replacement availability. Replacement availability depends on where your heifers come from. Are heifers raised on farm, bought, or some combination? Do you use sexed semen? If you do not have a heifer to replace a cow you want to cull, culling may not be a good strategy. Additionally, be aware of the quality of your incoming heifers. In most cases, the best genetics on the farm are in your heifers. Therefore, it’s important to realize that you are not replacing a cull cow with an identical animal but actually a (genetically) superior animal.
Calf Management Practices Impact Future
Production
Gone are the days when growth and health of dairy calves are
the only important outcomes expected with successful calf
management programs! We now understand that these
programs also impact a calf’s future performance. Known as
perinatal programming, management and nutritional
practices during early life have three to seven times more
influence on future milk production than sire selection. Our
understanding in this area has increased in recent years and
this will continue to be an actively studied area.
Consequently, the role of certain management practices
which control or impact future performance will become
better understood along with a continual refinement of
recommended nutritional and management practices in
heifers prior to puberty. When implementing practices on
farm, understanding the reasons behind these practices, why
they have changed over time, and how they can impact future
performance are important parts of managing heifer
programs.
Colostrum intake: Feeding four quarts of high quality
colostrum within six hours of life is important for healthy
calves. Antibodies are not absorbed across the placenta
because of the multiple tissue layers between the blood
supply to the placenta and uterus. Thus, calves must
absorb antibodies found in colostrum for early life
immunity against diseases. Failure to absorb an adequate
amount of IgG antibodies is known as failure of passive
transfer. Calves which do not absorb adequate IgG
antibodies have lower weight gain, increased risk for
disease and death, and decreased milk production during
their first lactation. (Additional information on feeding
colostrum is available in the article “Getting Dairy Calves
Off to a Good Start — The SIP Principle with
Colostrum”.)
Colostrum important for more than healthy calves:
Researchers estimate that feeding four versus two quarts
of colostrum to large breed calves may increase milk
production by 2,500 lbs. or more during the first
lactation. This production response is related to nutrients
and other components found in colostrum, in addition to
the antibodies. Colostrum contains growth factors,
hormones and other biologically active factors which
positively impact the development of the digestive tract.
These components of colostrum, in turn, enhance the
uptake and utilization of nutrients, especially those
associated with providing energy. This positive effect
continues throughout this calf’s life.
Calves are born with an immature immune system:
Newborns have an immature immune system which
takes 6 months or more to fully mature. Essentially, their
immune system has “no memory” and, as a result, does
not respond well when faced with a disease challenge.
Maternal antibodies from colostrum are essential to
protect the newborn for at least the first 2 to 4 months of
life. However, these maternal antibodies can interfere
with a calf’s ability to respond immunologically to
traditionally administered vaccines. To avoid the
influence of maternal antibodies, intranasal vaccines can
be used to vaccinate young calves to reduce the risk of
respiratory diseases. Intranasal vaccines elicit a local
immune response within the mucosa of the calf’s nose
and provide for a quick immune response, thus providing
disease protection for the calf. These vaccines
unfortunately only provide short term protection, usually
less than 30 days.
Pre-weaning growth rate impacts future milk yield: A
majority of studies have shown that higher pre-weaning
average daily gain positively impacts first-lactation milk
yield. Scientists from Cornell University estimated that for
each pound of daily gain, milk production increased by
1,540 lbs. in the first lactation or 6,000 lbs. over three
lactations. They suggested that calves should double their
birth weight by 56 days of life in order to achieve milk
production responses from early life nutrition. In an
analysis where many studies were evaluated, Gelsinger
and others at Penn State University concluded that pre-
weaned calves with average daily gains greater than 1.1
lbs./day have greater first-lactation milk yields.
Dairy Management Tip
Donna M. Amaral-Phillips UK Extension Dairy Nutritionist
3. Cow ranking. Consider ranking your cows accord-ing to their potential profitability. This allows you to easily identify the best cows to cull when you have an opportunity for voluntary culling. Addi-tionally, ranking cows allows you to determine how much it is worth to try and keep a cow (i.e. you would be more likely to treat a mastitis case for a cow ranked 10th than a cow ranked 350th in the herd). There are some herd management soft-ware programs that will rank cows for you. For example, the CowVal option in DairyComp will rank cows according to their value and their ex-pected value after becoming pregnant. Ranking cows allows you to consider many factors at once including production level, pregnancy status, dis-ease history (and likelihood of repeat), etc. Some-
times other factors can play into culling that don’t relate specifically to expected profit (i.e. cow tem-perament, etc.).
4. Good records are important. In order to rank
cows and to be able to estimate their future value, good record keeping is essential. Although most farmers tend to keep good production and repro-duction records, disease records are especially val-uable for culling decisions (yet often overlooked).
Culling is not only a science, but also an art. Unfortunate-ly, perfect prediction of exactly the best time to cull a cow is not possible. Dairy is a risk-filled business and there is always a risk that a cow will get a disease, abort a calf, or even die unexpectedly. There will always be some of these involuntary culls no matter how strategic your voluntary culling is.
To Keep or To Cull … continued
Obviously, appropriate growth post-weaning also is needed
to capitalize on this improvement in milk production during
the first lactation, and other management practices can
impact performance later in life.
Calves born to heat-stressed dams absorb fewer antibod-
ies: Heat stress to the dam does not alter the concentra-
tion of IgG or antibodies in colostrum. However, calves born
to heat-stressed dams absorb fewer antibodies, resulting in
higher rates of failed passive transfer. Thus, reducing heat
stress in dry cows impacts not only the body size of new-
born calves, but also their potential health.
Calves treated with antibiotics give less milk: A study
showed no difference in first-lactation milk production be-
tween calves with or without diarrhea; however, scouring
calves treated with antibiotics gave 1,086 lbs. less milk dur-
ing their first-lactation than those not treated (Soberon and
others 2012). These data do not indicate that antibiotics
should not be used when needed, but that prolonged dam-
age to the intestinal tract or other complications may occur.
Besides scours, respiratory disease is a common problem in
calves. Dr. McGuirk (University of Wisconsin) estimates that
three to four times more calves are affected with respirato-
ry problems than are treated or identified by producers.
Studies have shown decreased growth, decreased survival
to first calving, and increased age at calving in calves with
respiratory disease within the first 60 days following move-
ment to group housing (Stanton and others, 2012). Vac-
cines, minimizing stress, and providing proper ventilation in
the microenvironment around the calf without causing
drafts are important components in preventing respiratory
illness.
Dairy Management Tip … continued
How to Prevent Scours in Dairy Calves
By: Haley B. Reichenbach and Donna Amaral-Phillips
The term “scours” refers to an all-encompassing word for
diarrhea in many different species of animals. Scours is
specifically cited as “a case of diarrhea that requires
intervention for more than 24 hours,” . Scours can have life
threatening effects, commonly in newborn animals. Scours is
present in many different livestock industries however; the
dairy sector is highly impacted. In 2007, it was reported that
57% of weaning-age dairy calf mortality was caused by scours .
Maintaining satisfactory standards
of cleanliness and immunity are two
key targets when preventing scours
in calves. Common sense dictates
that the best way to prevent
bacterial or viral infections is to
eliminate areas in which bacteria
and viruses may thrive and to
strengthen the immune defense of
the susceptible animal.
Recognizing and Preventing Scours
Early detection is key in preventing
death caused by scours. Rectal temperature can help determine
the presence of scour-causing bacteria (temperatures
exceeding 103° F for more than one day in a row). Reduced
milk intake, weakness, or watery and/or bloody stool can
indicate the presence of a disease which causes scours.
Colostrum. Calves are born without immunity or the ability to
fight off a disease challenge. Calves acquire this immunity,
called passive immunity, primarily through consumption of
colostrum within the first six hours after birth. The current
recommendation for colostrum consumption for Holsteins or
other large breeds is 4 quarts given as 2 small bottles fed within
this six-hour window. Immunoglobulins present in the
colostrum, are used to fight the diarrhea-inducing bacteria that
the calf may encounter and antibodies within colostrum will not
be absorbed if not ingested soon after birth. Additionally, any
vaccination protection injected into the dam pre-partum, will
be delivered to the calf via the colostrum. Colostrum quality
must be considered as well. A refractometer or colostrometer
may be used to ensure this quality.
Health of Dam. Healthy cows rear healthy calves. Maintaining
proper nutrition and vaccinations for dams provides the calf
with a healthy start. This is simply another way to support the
immune system of the calf. “Close-up” areas (a pre-partum area
usually consisting of cows who will calve within the next three
weeks) should provide adequate space (one cow, one bed), and
effective heat abatement (heat stress abatement should begin
at 65° F) as overheated cows are correlated with poor
colostrum production. Vaccinating dams for protection against
scours in their calves should follow vaccine label directions and
generally occur 40 to 60 days prior to calving, and again three
weeks prior to calving.
Calf Housing. Facility design has a profound impact on calf
health. Air-flow resulting from proper ventilation is necessary to
remove pathogens from the air. However, housing for calves
should be draft-free at the level of the calf but still allowing for
air movement. In the winter, calf facilities
should have 4 air exchanges per hour. This
value increases with age and warmer weather .
Additionally, whether you prefer individual or
group housing, overcrowding should be
avoided. Each animal should have at least 30
square feet of space up to four months of age.
This area however, does not include the
additional space required for feeding.
General Sanitation. Common sense reminds
that pathogens often thrive in unsanitary
conditions. Cleaning and sanitizing equipment after every use
can prevent the spread of scours. This pertains to calf pails,
bottles, watering pails and any related equipment. Hutches and
individual calf pens should be washed and disinfected between
calves. Group housing equipment, such as nipples should be
replaced at least twice monthly and should be immediately
replaced upon a scours outbreak. Bedding should be regularly
replaced as well, more often for group housing.
Birthing Area. The first surfaces that the calf will encounter
are those within the calving pen. A clean calving pen is vital to
the healthy start of the calf. Calving pens that have been
infected by manure slurry from many different animals will
commonly infect newborn calves, as their gut is very absorptive
during these first few hours of life. To maintain a clean calving
pen, cows should not be brought into the pen multiple days
prior to calving. Decreasing this waiting time will contribute to a
cleaner pen.
While scours can often seem inevitable as so many farms are
affected, following the aforementioned practices can have a
large impact on decreasing incidences. The first step to
reducing the impact of scours or any form of infectious disease
in the dairy industry is prevention.
Getting Dairy Calves Off to a Good Start – The
SIP Principle with Colostrum
By: Maurice L. Eastridge, The Ohio State University
As soon as the dairy calf exits the uterus of the cow, the
maternal nutrition and protection from disease by blood
transfer of nutrients and immune cells directly to the fetus
ceases. This nutrition and immunity now shifts to absorption of
nutrients and immune cells found within colostrum to further
protect the newborn and get it off to a good start. It has been
well documented for years that consumption of colostrum, the
first mammary gland secretion from the dam, is essential for low
calf morbidity and mortality. It’s that simple, but not exactly.
This process, called S I P, involves the:
Supply of colostrum,
Immunoglobulin (Ig) concentration, and
Pathogens of low presence in colostrum
Supply of Colostrum
Many farms struggle today with having an adequate supply of
high-quality colostrum for feeding calves; thus, most farms will
have some frozen as a back-up plan. It has been perplexing for
years as to what factors affect the yield of colostrum. In a recent
study conducted with Holstein cows at the University of Bern in
Switzerland, first-lactation cows produced about 10 lb of
colostrum (range = 4 to 24 lb), and cows with two or more
lactations averaged 43 lb (3 to 46 lb). Although the average yield
would provide a sufficient supply, some cows within the study
yielded very low amounts of colostrum. Cows obviously calve at
different times of the day, which results in different time
intervals to milking time, but in this study, time from calving to
milking did not affect colostrum yield. In addition, the colostrum
yield was poorly correlated to milk yield for the entire lactation.
Risk factors suggested for potentially reducing colostrum yield
have included a shortened dry period, low protein and energy
intakes during the dry period, and heat stress, but limited
scientific evidence is available to directly identify the major risk
factors for reducing colostrum yield. Among several studies,
nutrition of the dry cow has generally resulted in minimal effects
on colostrum yield. In a recent study conducted at Ohio State
University (unpublished), dry cows were overstocked at the
feedbunk (0.88 headlocks per cow) or understocked (1.17
headlocks per cow) in the far-off period or close-up period.
Holstein cows that were overstocked during the far-off period
tended to produce less colostrum than cows understocked for
the entire dry period (12.6 versus 19.3 lb, respectively).
However, given that the risk for an inadequate supply of
colostrum from every cow exists on every dairy farm, frozen,
high-quality colostrum should be available or a stocked supply of
colostrum replacer be on hand, preferably formulated with
bovine immunoglobulins (Ig).
Immunoglobulin Concentration
For years, research has
focused on the quality
of colostrum (i.e.,
concentration of
immunoglobulins) as
the primary factor
affecting the level of
immunity in the calf
because it was
assumed that you
always feed the same
amount of colostrum,
generally about 4 quarts or 4 liters within the first 6 hours of
birth. The sooner colostrum is fed, the more Ig are absorbed
because gut closure increases with age and exposure to
bacteria; however, timing of feeding colostrum varies. Some of
this variation in timing relates to when the cow calves, how
frequent the calving pen is checked, when she gets milked (with
herd or bucket milker), and the actual lag that occurs from the
time the colostrum is harvested until the calf is fed.
In addition, we used to check the quality of colostrum by
primarily using a colostrometer, but today we encourage the use
of a Brix refractometer (greater than a 22 percent reading on a
Brix refractometer recommended, which is equivalent to greater
than 50 g/L of IgG). A colostrometer is easy to break and then
you have a mercury issue, and temperature of the milk can
affect the readings (room temperature preferred, 72°F). A Brix
refractometer also can be used to check the serum protein, an
indicator of passive transfer of immunity from the colostrum
(greater than 5 g/100 ml of serum protein or 10 g/L of serum IgG
is suggested, which is equivalent to a greater than 8 percent Brix
reading).
There does not appear to be a high correlation of nutrition of
the dam during the dry period, photoperiod, or the yield of
colostrum on the Ig concentration in colostrum. Also, in an
Israeli study with Holstein cows, Ig concentration in colostrum
was not affected by a 60- versus 40-day dry period. Thus, the
specific causative factors of low concentration of Ig in colostrum
are not defined.
Based on the concentrations of Ig in the colostrum, we can ad-
just the amount of colostrum fed to provide adequate intake of
Ig. Colostrum should have greater than 50 g/L of IgG. Thus, a
calf fed 4 L of colostrum with 60 g/L of IgG would consume 240
g of IgG. So if the Ig in colostrum is marginal and higher-quality
colostrum is not available, the amount of colostrum can be in-
creased by 1 or 2 qt (L) as needed. For example, if the colos-
trum contains 48 g/L of IgG, then 5 L of colostrum would need
to be fed to provide the 240 g intake of IgG.
The amount of Ig consumed is more important than the actual
concentration of Ig in the colostrum. Intake of IgG is of primary
importance, but there are other Ig and potential immune stimu-
lators in colostrum. In a recent study at Virginia Tech University,
it was observed that maternal immune cells in colostrum were
important in enhancing neonatal immunity during the first
month of life. Of course, colostrum is rich in nutrients and other
growth factors and hormones to enhance the neonate's start in
life and possibly production later in life.
Reducing Pathogen Load
High bacterial counts in colostrum enhance gut closure to ab-
sorption of Ig and increase the risk for failure of passive transfer
and diarrhea. Colostrum at feeding time should contain less
than 100,000 cfu of bacteria using the standard plate count.
Some calf care specialists suggest that low bacteria count in the
colostrum is as important, possibly even more important, than
the Ig concentration in providing for adequate passive transfer
of immunity. Keeping the bacteria count low begins with the
equipment used for milking the dam and then continues into
how the colostrum is stored if it is not fed immediately, and of
course, the utensils used in feeding the colostrum to the calf.
Colostrum should be fed immediately after it is harvested, or
chilled for delayed feeding and then warmed to 100° to 105°F
at feeding. If colostrum is not fed within about 48 hours after
harvest, it should be frozen.
High-quality colostrum relative to Ig concentration can sudden-
ly become poor quality because of dirty equipment used to
harvest and feed the colostrum. Oftentimes, the equipment
looks clean, but it may be a simple gasket or valve that is con-
taminating the entire supply of colostrum. So proper cleaning
of equipment, including valves and other potential crevices,
after each contact with milk is very important. Then the equip-
ment must be kept dry and stored in a low-dust environment.
Colostrum can be pasteurized without denaturing the Ig, but
the temperature should be held at 140°F for 60 minutes (versus
30 minutes at 145°F for whole milk) and then the colostrum
should be cooled rapidly. Also, some manufacturers of pasteur-
izers have developed special bags for use in their equipment to
provide for uniform heating and to ease storage of colostrum
after pasteurization.
The other important step in reducing pathogen load to the
newborn is providing a clean, dry calving environment. So,
cleanliness of the maternity pen is important for reducing the
intake of pathogens when the calf’s mouth touches the envi-
ronment. Then clean, dry bedding in the housing area is im-
portant in reducing bacterial growth in the calf’s environment.
Summary
An adequate Supply of colostrum of high Ig concentration and
with low Pathogen load is critical for the calf to get off to a
good start. The management factors that specifically cause low
yield and quality of colostrum are unclear. However, extreme
variations in yield and quality of colostrum occur on dairy
farms, and thus proper measurement of colostrum Ig concen-
tration is essential. With this information, the amount of colos-
trum fed can be adjusted, an alternative source can be used, or
a colostrum replacer can be used. Whichever is used to provide
the Ig to the calf, a low bacteria count is essential for adequate
absorption of the Ig to occur. Colostrum consumed by the calf is
a nutrient- and Ig-dense food with a low bacterial count if har-
vested, handled, and fed properly.
Getting Dairy Calves Off to a Good Start – The
SIP Principle with Colostrum...continued