Production responses of lactating dairy cows and heifers given thiabendazole at parturition.

A field trial was conducted to examine the effects on productivity of dairy cattle in 6 herds given thiabendazole at parturition. Criteria examined were milk and fat production, calving interval, services per conception, culling rate, and (in a subset of cows) hematologic response. Analysis of the data for all cows as a group did not indicate a significant effect. For first-calf heifers in 1 herd, a significant (P less than 0.01) and economically important increase in milk production was observed; why the effect was seen was not determined.