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0706 PD: Developing quality dairy replacement heifers

John K. Bernard Published on 07 August 2006

A lot of work and care is required to develop newborn calves into productive, lactating cows. When managed properly, replacement heifers should grow at a rate that allows them to calve at 24 months of age or less. However, a recent report indicated the average age of Holsteins at first calving was 26.9 months, so there are opportunities for improvement. Also, the mortality rate on many farms is higher than desired, reducing the number of potential replacement heifers.

Much of the success, or failure, of the replacement heifer program is related to care provided during the first two months of life. Dr. Sandra Godden of the University of Minnesota states, “31 percent of all dairy heifer mortality during the first 21 days could be prevented with improved colostrum management.”

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Providing a clean calving environment and timely feeding of good colostrum is essential for getting calves off to a good start. After weaning, providing balanced diets (along with adoption of good preventive health programs) will ensure that calves are ready to breed by 13 months of age so they can calve at 24 months of age or less and produce up to their potential.

Calving environment
Successful heifer replacement programs begin with providing the cow a clean environment to calve in. The calving area should be easy to monitor so assistance can be provided when needed. Ideally, each dairy would have calving pens that provide easy access, are easy to clean and provide a means of providing any assistance required to the cow and calf. After birth and the calf is breathing normally, the naval should be dipped with a 7 percent tincture of iodine and immediately removed from the dam to minimize exposure to pathogens that may be present.

A large number of disease organisms are transmitted through fecal contamination and direct contact with the dam or other cows in the calving area. Removing the calf from the calving area into a clean environment reduces exposure to these pathogens and reduces the potential for sickness. After the calf has been removed to a clean area, high quality colostrum should be fed as quickly as possible.

Colostrum feeding and management
Calves are born without any natural immunity to disease and depend on colostrum intake to provide immunoglobulins (IgG) for protection against diseases and nutrients in support of life. Absorption of IgG in the small intestine decreases approximately 5 percent per hour, so that essentially no absorption occurs after 24 hours of birth. In addition to providing IgG, colostrum also binds pathogens, preventing them from colonizing in the small intestine and causing sickness.

To achieve successful passive transfer of immunity, it is recommended calves be fed 2 to 4 quarts of high-quality colostrum within two hours of birth and another 2 quarts 12 hours later to provide the calf adequate immunity and nutrients to get it off to a good start.

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According to the 2002 National Animal Health Monitoring (NAHM) survey, 56.1 percent of calves were removed from the cow immediately and fed colostrum, but the remaining calves had the opportunity to nurse the dam. The mortality rate of calves left with their dam for 12 to 24 hours was twice that of calves removed from their dam within four hours of birth. The reason for the higher mortality rate is related to increased exposure to disease pathogens and failure of passive transfer of immunity (FPT).

Calves left with their dam do not always consume adequate amounts of colostrum, or colostrum quality is low or poor. Field data from a wet calf grower in Florida indicated approximately 30 percent of calves with FPT died. Those that did not die required more antibiotic treatments, increasing rearing cost. Calves that are sick early in life and recover do not grow as well or produce as much milk as calves that do not get sick.

Colostrum quality
Not all colostrum provides adequate amounts of IgG to ensure successful passive transfer of immunity. The IgG quality is affected by vaccination status, nutrition, stress, age, breed and other factors. A good preventive health program is the first step in stimulating the production of high IgG concentrations in the colostrum. Choice of vaccine, time administered and route of administration all affect the effectiveness of a vaccine to stimulate an effective immune response.

Diets should be balanced to provide adequate protein, energy, macrominerals, trace minerals and vitamins using palatable ingredients that are readily consumed and free of mycotoxins. During times of heat stress, supplemental cooling should be provided to minimize heat stress and maintain intake. Even when all steps are taken to provide each cow with the opportunity to produce high-quality colostrum, some do not.

The quality of colostrum should be measured, and only high-quality colostrum from cows tested free of Johne’s, BLV and BVD should be fed. Colostrum quality can be measured quickly on the farm using a colostrometer. The colostrometer works on the specific gravity of the colostrum, so the higher it floats, the better the colostrum quality. The colostrometer is marked with green, yellow and red indicators. Green indicates high concentrations of IgG; yellow, intermediate; and red, poor IgG concentrations. Colostrum that measures green can be fed without any problems.

Colostrum that measures green can be frozen for later use when high-quality colostrum is not available. When colostrum has a lower quality (yellow), a colostrum supplement or replacement should be mixed with the colostrum to provide adequate IgG. Poor quality colostrum (red) should only be fed after the first day of life, as it will result in FPT.

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The colostrometer readings are sensitive to the temperature of colostrum. Cooler temperatures overestimate IgG concentrations, whereas warmer temperatures underestimate IgG concentrations. Colostrum should be cooled (or warmed when feeding frozen colostrum) to approximately 68º to 74ºF before testing.

Pooled colostrum
The NAHM survey indicated many producers (70.6 percent) feed pooled colostrum. Many producers feed pooled colostrum to reduce the risk of FPT, but feeding pooled colostrum spreads diseases such as Johne’s, BLV or BVD to a large number of calves. These diseases reduce milk yield and reproductive performance and increase culling and mortality rates. For successful control of diseases such as Johne’s, pooled colostrum should not be fed.

Another problem associated with feeding pooled colostrum is bacterial contamination. If a strict sanitation protocol is not used to keep containers clean, pooled colostrum is quickly contaminated with bacteria that can cause a severe disease outbreak, resulting in high death losses. Calves fed contaminated colostrum frequently die within one to three days after birth.

If pooled colostrum is used, a sample should be collected routinely for analysis of bacterial concentrations to monitor sanitation. A strict sanitation protocol must be used for cleaning containers used for handling colostrum (individual or pooled).

Amount of colostrum fed
As indicated earlier, most recommend feeding at least 4 quarts of colostrum within two hours of birth plus an additional 2 quarts 12 hours later. A recent report suggests there are long-term benefits of feeding 4 quarts of high-quality colostrum immediately after birth. The researchers fed either 2 or 4 quarts of good colostrum immediately after birth, plus an additional 2 quarts 12 hours later. Calves were fed whole milk until weaning.

Calves fed 4 quarts of colostrum at birth had fewer health disorders and lower veterinary cost, which is consistent with previous research. Because calves have fewer health disorders and possibly because of positive effects on nutrient absorption, these calves also had a higher estimated average daily gain (ADG) and were bred at an earlier age.

The authors suggested there was possibly a positive effect on mammary development because 305-d mature equivalent (ME) lactation records for both first and second lactation were approximately 2,000 to 3,000 pounds higher than for calves fed only 2 quarts of colostrum at birth. The number of animals culled before completing the second lactation was almost twice as high for the group fed 2 quarts of colostrum compared with that of the group fed 4 quarts of colostrum at birth.

Although these data represent the results of only one trial, they do suggest good colostrum management not only reduces health disorders in calves but may improve nutrient digestion and metabolism in the young calf, allowing it to grow more efficiently.

There is additional research supporting these observations, suggesting the positive nutrient balance positively influences endocrine function related to mammary development. These improvements may also promote other positive changes that support improved milk production and improve the odds of the animal staying in the herd longer.

Colostrum supplements and replacements
There are numerous colostrum supplements and replacers on the market that are regulated by the USDA Center for Veterinary Biologics. These products were developed to provide a means of supplying IgG to the newborn calf when high-quality colostrum is not available or to provide an alternative to disease control.

Colostrum supplements are produced from bovine colostrum or other milk products or bovine serum and are designed to be mixed with lower quality colostrum to increase IgG intake. Colostrum supplements contain less than 100 grams of IgG per dose and cannot be used to effectively replace good colostrum. These products are intended to be used as a supplement to lower quality colostrum to increase IgG intake and prevent FPT.

However, IgG absorption is low for most of these products, resulting in higher-than-desired rates of FPT. Egg-based supplements are poorly absorbed, whereas products based on colostrum or whey have variable IgG absorption efficiencies. Colostrum replacements are produced from bovine serum-based products and provide 100 grams or more of IgG per dose. These products also contain fat, protein, vitamins and minerals, and they can be fed in place of colostrum. Research indicates the IgG in colostrum replacements is absorbed as effectively as IgG provided by colostrum to support successful passive transfer, when fed in adequate amounts. The success rate of colostrum replacements is related to feeding adequate amounts to ensure successful passive transfer of immunity.

The amount of IgG that must be fed to provide 100 grams of IgG, which is considered the minimum for successful passive transfer, varies with absorption efficiency. Data indicate at least 150 to 200 grams of IgG must be fed to prevent FPT. Producers should check products to see they will provide adequate amounts of IgG when fed according to directions and that the product is based on bovine serum.

Measuring IgG status
Failure of passive transfer is generally defined as blood IgG concentrations less than 10 milligrams per milliliter at 24 to 48 hours of age. The success or failure of passive transfer can be determined using commercial IgG test kits or by measuring blood protein concentrations. Many of the IgG test kits are more complicated to run, so most producers use a refractometer to measure blood or serum protein concentrations. Total serum protein concentrations are directly related to IgG concentrations in the blood and are easier to measure.

The procedure consists of collecting a whole blood sample from a calf anytime between 24 and 48 hours after birth. The sample is allowed to clot or is spun in a centrifuge to separate the serum. The serum is collected and placed on a refractometer, which directly measures the total protein. Total serum protein concentrations greater than 5.5 milligrams per deciliter (about 0.1 quart) are considered to indicate successful passive transfer. Concentrations of 5.0 to 5.4 milligrams per deciliter indicate moderately successful passive transfer, and concentrations less than 5.0 indicate a failure of passive transfer. This simple method can be helpful in troubleshooting health problems related to colostrum management.

Whole milk or milk replacer
Calves can be successfully raised on either whole milk or milk replacers. Whole milk provides more nutrients, which should support faster gains, but feeding raw whole milk can transmit diseases such as Johne’s or BLV, spread mastitis-causing organisms to young calves and can result in antibiotic residues if a young calf were sold for meat.

If whole milk is fed to replacement heifers, it should pasteurized. Feeding properly pasteurized milk improves growth rates and reduces the number of days calves have diarrhea or pneumonia. It is essential pasteurization be done consistently from day to day and that the equipment be thoroughly cleaned to prevent bacterial contamination.

Milk that is batch-pasteurized should be heated to 145ºF for 30 minutes, whereas milk that is flash-pasteurized should be heated to 162ºF for 15 seconds. All employees should be trained on the importance of following operating procedures for pasteurization and sanitation. Producers should keep a daily log that records who pasteurized milk, pasteurization temperatures and times and cleaning routines.

Traditionally, producers have had good results feeding all-milk replacers containing 20 percent protein and 20 percent fat. Although milk replacers can be made using plant proteins to reduce cost, calf performance is not as good.

More recently, higher protein milk replacers (28 percent protein and 15 to 20 percent fat) fed at rates of 2.5 pounds per day have been used. These products have been shown to increase growth rates and promote greater muscle and frame development but increase milk replacer and labor cost (although cost per pound of gain is equal or lower to traditional programs).

These programs are thought to enhance mammary development as well. However, these products may not be as effective when colostrum management is not adequate or if there is increased disease potential. A recent trial with calves that did not have adequate transfer of immunity and were challenged with coronavirus had greater mortality and incidence of scours, although they gained more weight throughout the trial.

Weaning
Age at weaning varies from farm to farm, with a range of 4 to 8 weeks old. Calves can be successfully weaned from milk or milk replacer when starter intake exceeds 2 pounds per day for two consecutive days. The amount of stress the calf is subjected to increases at weaning as diets change, when calves are moved out of hutches or individual pens into a group housing environment and as they are exposed to other calves. Intake often drops, reducing nutrients needed for growth and immune function which increases their susceptibility to respiratory disease. To minimize stress, calves should remain in the same environment for an additional week.

When moved to group housing, calves should be grouped by body size and kept in small groups (less than seven head). Adequate feedbunk space should be provided. Feed should be changed gradually. Other activities that increase stress (vaccinations, dehorning, etc.) should be spread out rather than done at weaning. Reducing stress will make the transition for the calf go more smoothly and keep them healthier.

Summary
Getting calves off to a good start in life will allow the calf the opportunity to grow into a productive cow. Colostrum management is critical for minimizing disease and optimizing growth. At least 1 gallon of high-quality colostrum should be fed within the first two hours of life, with an additional 2 quarts 12 hours later to provide successful passive immunity. When high-quality colostrum is not available or there is a question about the disease status of a cow, 150 to 200 grams of a colostrum replacer can be fed to provide successful passive transfer of immunity. Serum protein concentrations can be measured to determine the success (or failure) of passive transfer of immunity. PD

References omitted due to space but are available upon request.

—From 2006 Florida and Georgia Dairy Road Show Proceedings

John K. Bernard, Department of Animal and Dairy Science, University of Georgia

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