Effects of passive immunity on growth and survival in the dairy heifer.

Effects of 24 to 48 h serum Ig concentration on growth and survival of 1000 Holstein heifer calves were evaluated. Average serum Ig for all calves was 25.71 (SD = 19.06) mg/ml with a range of .05 to 108.27. Serum Ig concentrations were below 12 mg/ml in 28% of the heifers. Both season and age of dam contributed significantly to the variation in 24 to 48 h concentrations of serum Ig. Concentration of serum Ig at 24 to 48 h was a significant source of variation affecting average daily gain through the first 180 d of life. Seasonal factors also were significant in influencing rate of gain from birth to 180 d. Age of dam was a significant source of variation in calf weight gains but only for the first 35 d. Mortality was 6.78% for heifers with less than 12 mg/ml serum Ig at 24 to 48 h as compared with 3.33% mortality for calves with greater than 12 mg/ml concentration.