The Transfer of Passive Immunity to Neonatal Dairy Calves

Cathleen Williams  |  7/28/2005 12:58:27 AM

Gina E. Goodier, Graduate Assistant, Department of Dairy Science
Cathleen Williams, Assistant Professor, Department of Dairy Science

A healthy calf crop provides replacement animals for the future of the dairy operation. However, a busy work environment often causes the neonatal calf to become overlooked, leading to consequences that may be irreversible. It is important to understand that the neonate must consume sufficient colostrum as soon after birth as possible to achieve the needed passive immunity to survive the first few weeks of life.

Immunity refers to the body being able to distinguish "self" from "non-self." It does this by "remembering" individual foreign substances called antigens and mounting an attack directly using lymphocytes (white blood cells) or specific proteins called antibodies, to destroy the antigens or pathogens. Antibodies belong to a special class of proteins called immunoglobulins (Igs). These Igs are produced by B cells in the bone marrow and work to destroy the antigens. Igs are found in colostrum and blood and provide the calf with the immunity to protect itself against pathogens encountered during everyday life.

Bovine colostrum contains three types of Igs designated as IgG, IgM, and IgA. Each of these Igs plays a different role in identifying and protecting against pathogens. IgG is the smallest of the Igs but is present in the greatest concentration. It can move from the blood into the tissues where it seeks out and destroys invading pathogens. IgM is a larger molecule that remains in the blood where it protects against bacteria that may invade the body. IgM is considered as the first line of defense against septicemia. IgA attaches to the mucosal cells lining the intestine and protects against invading pathogens. Feeding colostrum for the first three days of life will provide IgA to protect the gut against pathogens.

Igs begin to move into the mammary secretions as colostrum starts forming prior to calving. Colostrum contains 3 to 5 times more protein than normal milk. Most of this increase in protein content is from accumulation of Igs, particularly IgG. The actual amount of Igs present can be influenced by many factors such as age, parity, nutritional status, breed, etc. Although colostrum quality can vary from cow to cow, it is important that the first colostrum a calf receives contains sufficient quantity of Igs. One way to determine colostrum quality is with a colostrometer. Good quality colostrum will have an Ig concentration greater that 50 mg/ml. Make sure to read the directions that come with the colostrometer, and let the colostrum cool to 72EF for the most accurate reading.

Calves must absorb the Igs in colostrum as whole protein molecules to obtain passive immunity. However, the cells of the small intestine mature rapidly and lose their ability to absorb these protein molecules. The efficiency of IgG absorption is highest immediately after birth and declines to nearly zero by 24 hours of age. After 24 hours, very little IgG consumed in colostrum or transition milk will be absorbed.

Another factor to consider is how should the colostrum be fed? Using a nipple bottle or esophageal feeder lets you know exactly how much colostrum the calf consumed. Do not rely on the calf to nurse from the dam. Most calves do not consume adequate amounts of colostrum when allowed to only nurse the dam. Studies have indicated that udder conformation of the dam can affect time to first suckling. Calves born to dams having udder floors 2 feet or less above the ground delayed first suckling by nearly 4 hours. The delay time increased as udders became more pendulous and moved closer to the ground.

Recommendation

Colostrum quality and feeding time are critical factors in determining if a calf receives adequate passive immunity. Calves should be fed at least 3 quarts of first milking colostrum by 1 hour of age and again 12 hours later. If you have determined that colostrum quality is adequate (greater than 50 mg/m), 2 quarts may be fed at the first feeding. With smaller Holstein or Jersey calves, 2 to 2 1/2 quarts may be sufficient. An esophageal feeder should be used if the calf will not consume sufficient colostrum. Continue feeding colostrum or transition milk for the first 3 days. It is highly nutritious and will provide some local protection in the gut from invading pathogens.

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