THE EFFECTS OF PASSIVE IMMUNITY ON GROWTH AND SURVIVAL IN THE DAIRY HEIFER (IMMUNOGLOBULINS, MORBIDITY, NEONATE, MORTALITY, COLOSTRUM).

One thousand Holstein-Friesian heifer calves were studied to evaluate the effects of colostrum-derived 24 to 48 h serum Ig concentrations on growth and survival. The rate of growth increased as 24 to 48 h serum Ig concentrations increased. Calves born to first-calf heifers had higher 24 to 48 h serum Ig concentrations and gained weight at a higher rate of gain than heifers born to 3-year-old and older cows. The concentration of serum Ig at 24 to 48 h in the dairy heifer is a significant source of variation affecting average daily gain through the first 180 d of life. Seasonal factors were also significant in influencing rate of gain from birth to 6 months. Age of dam was a significant source of variation in calf weight gains, but only for the first 35 d of life. Approximately 28% of the calves absorbed less than 12 mg/ml of maternally-derived antibody. Heifers in this category suffered a death loss of 6.78% compared to only a 2.59% loss for heifers absorbing greater than 40 mg/ml Ig. Both season and age of dam were significant in affecting the concentration of 24 to 48 h serum Ig acquired. Forty-nine percent of the variation in 35 d serum Ig can be attributed to the variation found at 24 to 48 h. The data presented here indicate that proper management of factors influencing the absorption of colostral immunoglobulins by the neonatal dairy heifer would enhance the replacement rearing program