Environment, dam, management: Factors influencing passive transfer of immunoglobulins to neonatal calves

continued on page 2 Manuel Chamorro, DVM Clinical Instructor College of Veterinary Medicine The bovine fetus has a type of placentation that does not permit contact between maternal and fetal blood and therefore does not permit passive transfer of immunoglobulins (Ig) from the mother to her fetus. The bovine calf is born agammaglobulinemic and depends on the intake of an adequate amount of maternal colostrum to provide antibodies and other immune factors that confer protective immunity against environmental pathogens from the early postnatal period until the third or fourth month of life. Many factors related to the calf, the environment, the dam and management can influence the passive transfer of Ig to neonatal calves (5, 9, 24, 46). Inadequate intake of colostrum immediately after birth, whether in quantity or quality, results in partial or complete failure of passive transfer (FPT) of Ig, which has been considered the most important risk factor for morbidity and mortality in neonatal beef and dairy calves (5, 9, 14, 16, 22, 30, 36, 46, 47). Various methods used to diagnose FPT have been reviewed by others (24, 30). The level of IgG in serum has been considered the most accurate method to diagnose FPT in calves. The range of values considered for failure are < 8 g/L for total failure, >8 but <10 g/L for partial failure, and >10 g/L for adequate transfer of IgG (30). Some authors consider only > 10 g/L for adequate transfer and <10 g/L for inadequate transfer of IgG (5, 9, 14, 15, 18, 22, 46). Various studies have shown that the prevalence of FPT in dairy calves may be around 10-35% (24, 30, 46). One study from USDA reported that more than 40% of dairy heifer calves have < 10 g/L in serum in the first day of life (51). In beef cattle, around 11-31% of calves reportedly achieved < 8 g/L during the first day of life (16, 29, 36). There are direct associations between FPT and presentation of disease (septicemia, diarrhea, pneumonia) and mortality in calves during the pre-weaning period. Some studies have shown that calves with FPT (< 8 g/L) are between 1.6 and 9.5 times more likely to become ill, and between 2.7 and 5.4 times more likely to die than calves with adequate passive transfer during the first months of life (16, 36, 37, 40). At the same time the performance of calves that had FPT is decreased compared to calves with adequate transfer of Ig. The average weight at weaning for calves with adequate Ig transfer can be 6-34 lb more than calves with FPT (14, 16, 17, 36, 40). All of this leads to economic losses due to reduced growth, suboptimal reproductive performance, treatment costs and death losses. An adequate colostrum management program and the early detection and treatment of calves suspected of FPT is required to improve the pre-weaning health and performance of the young stock in dairy and beef herds. The following will discuss in depth the factors that influence the Ig absorption process and different management and product alternatives that producers have to prevent FPT in calves.