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