863
Relationship between birth weight and calving ease with passive transfer of immunoglobulins in neonatal beef calves
The absorption of immunoglobulins (Ig) found in the colostrum is a passive transfer of immunity that neonatal calves will receive from their dams. Calves that do not receive adequate levels of Ig from their dams can experience increased morbidity and mortality. Primiparous commercial crossbred beef heifers (n = 53) were used to evaluate the relationship of Ig absorption from colostrum and passive transfer of immunity on various neonatal traits. Heifers calved in March and April. Females were kept in a dry lot and fed a total mixed ration meeting 100% of NRC requirements through parturition. Onset of the third stage of labor, time to birth, time to stand, and time of first nursing were recorded. Calving ease (CE; 1 = no assistance, 5 = caesarian section), calf vigor (CV), birth weight, and 24 h blood samples for serum Ig were taken from each calf via jugular venipuncture. Mothering score, colostrum samples for colostral Ig, weight, body condition score, udder suspension (1 = broken floor, 9 = very tight), and teat size (1 = very large, 9 = very small) were recorded from the dams. All statistical analyses were conducted using Proc Reg and Proc Corr in SAS. There was a negative correlation between serum IgG and CE (P = 0.01), positive correlations between birth weight and CE (P < 0.001), and udder suspension and teat size (P = 0.001). A tendency for a negative correlation was found between serum IgG and birth weight (P = 0.11) and a positive correlation between serum IgG and teat size (P = 0.10). After correlations were found, stepwise regression calculations were completed on all significant correlative variables. A linear regression was found between CE and serum IgG (P = 0.01), and quadratic regression between birth weight and serum IgG (P = 0.04). Difficulties during third stage labor increased as calf birth weight increased. The increases in CE scores were associated with decreased serum IgG found in the calf after 24 h. This depression of serum IgG due to calving difficulty may impair the ability of calves to adequately defend against pathogen exposure and may influence subsequent growth and performance.
Keywords:
beef, immunoglobulins, neonate