EFFECT OF THE USE OF BOVINE SOMATOTROPIN ON CULLING PRACTICES IN 32 DAIRY HERDS IN INDIANA, MICHIGAN, AND OHIO

Data from 5468 Holstein dairy cows in 32 herds were used to determine the effect of the use of bovine somatotropin (bST) on culling practice s over a 13-mo period. After an initial herd inventory, monthly inform ation regarding cow entry and exit from the herds was obtained by seve n participating veterinarians. Culling was coded by farmers for the fo llowing reasons: low production, reproduction, somatic cell count, mas titis, sickness, dairy purposes, lameness, death, and other. In the co ntrol herds, cows were not treated with bST during the trial. Adopter herds were defined as herds that utilized supplemental bST for greater than or equal to 25% of the cow-days during the trial. Mean herd use of bST in adopter herds was 38.6%. No difference in the number of cows culled per cow-day at risk was detected between control and adopter h erds (0.09 and 0.11%, respectively). Amount of in-herd use of bST was unrelated to culling. No significant differences were determined betwe en adopter and control herds in the percentage of cows that were culle d for any of the nine possible culling reasons. The results of this st udy suggest that culling patterns in herds that use bST are unaffected for at least the first year after adoption.