Getting enough high quality colostrum into a new born calf is the number one priority for the dairy farmer seeking to minimize calf death loss, improve calf health and positively affect future milk production. Colostrum is the first “milk” produced after calving and contains maternal antibodies, called immunoglobulins, often referred to as IgG’s. In addition, colostrum has a high content of protein, energy and vitamins. Calves are born with an immature or non-active immune system because antibodies are not transferred across the placenta in cattle pregnancies. At and immediately after birth, the calf’s gastrointestinal tract has the ability to absorb immunoglobulins contained in colostrum, from the small intestine. This passive immunity transfer will protect the newborn calf for at least the first 2 to 4 months of life until its own immune system begins to mature.
Timing is critical because IgG absorption across the gut is most efficient in the first 4 hours of life. Some literature says that on average by 6 hours after birth, there is a 33% decline in the ability of the gut wall to absorb IgG’s. By 24 hours after birth, the gut is closed and no longer capable of absorbing the IgG molecules. The sooner after birth that a calf is able to ingest colostrum, the better chance it has of successfully getting this transfer of immunity. I have seen publications that say get colostrum into calves within an hour of birth, but the general recommendation is a first feeding of colostrum within 3 hours of birth, followed by another smaller feeding within 12 hours after birth.
Successful transfer of immunity depends not only on timing but also on the quantity of IgG ingested. According to an Iowa State University Extension publication, calves should consume 10-12% of their birthweight as colostrum within 8 hours after birth. The common recommendation today is to give 4 quarts of colostrum within the first 4 hours, remembering that sooner is better, and then follow up with another 2 quarts 6-8 hours after birth but no later than 12 hours. In a lighter birthweight breed like Jersey, some publications recommend 3 quarts of colostrum within the first 3-4 hours and another 2-3 quarts by 6-8 hours after birth. The goal is to provide between 100 to 150 grams (454 grams per pound) of IgG as soon as possible.
Not just quantity but quality is important when it comes to colostrum. Colostrum quality can differ between cows. Factors that affect the amount of IgG’s in colostrum include the immune status of the dam with regards to the pathogens she has been exposed to, her vaccination level, the length of the dry period and the nutrition received during that dry period, the age of the cow, the season of the year and the breed of cow. In addition, bacteria from dirty teat ends or udders or milking equipment not properly cleaned can contaminate colostrum and lower the quality. Colostrum quality is determined by the amount of milligrams (mg) of IgG per milliliter (ml) and bacterial counts. High quality colostrum is defined as 50 mg/ml or greater of IgG and should have a total bacteria count of less than 100,000 cfu/ml and less than 10,000 cfu/ml total coliform count. The most reliable methods for measuring colostrum quality on the farm are the use of a colostrometer or a brix refractometer.
The colostrometer is a thermometer like glass tube that measures specific gravity and uses a color-coded scale calibrated in milligrams per milliliter. To use, place it in a cylinder of colostrum and allow it to float. The color of the scale floating above the colostrum indicates general colostrum quality. Typically a green test results indicates IgG levels above 50 mg/ml, yellow indicates 20-50 and red indicates low quality colostrum below 20 mg/ml. Readings are most accurate at a room temperature of 72 degrees F. Within the past several years, the brix refractometer has become more popular to measure colostrum quality. The brix refractometer measures the amount of sucrose in a solution and there is a good correlation between the brix reading and the IgG level in colostrum. Generally, a brix value of 22% corresponds to an IgG level of 50 mg/ml. Therefore brix readings of 22% and higher indicate a high quality colostrum. The brix refractometer is easy to use, less fragile than the colostrometer and not dependent upon temperature.
Storing high quality surplus colostrum is a good management practice. Do not let colostrum sit at room temperature; even half an hour at room temperatures during the summer may allow bacterial populations to double. Refrigerate colostrum at less than 40 degrees F for no more than 24 hours. Even at refrigerator temperatures, bacterial growth reaches unacceptable levels by 24 hours. Freezing is the best alternative for longer-term colostrum storage. Colostrum may be frozen (at -5°F) for up to a year without significant decomposition of antibodies.