Effect of Thyroprotein Feeding on Dairy Cows

Abstract

Sixty-three cows fed no thyroprotein averaged 7,265kg milk (308-day, mature equivalent compared to 7,237kg averaged by 63 cows fed 10g thyroprotein daily after 50 days postpartum. The maximum increase in milk production from thyroprotein feeding occurred during the first two weeks of feeding and amounted to a 7.0% increase over the control cows. From the 22nd to 42nd weeks of lactation milk production of thyroprotein-fed cows was less than that of controls. Milk fat tests were raised 0.41% (P<.10) for two weeks. Differences in lactation milk yield, fat test, and milk protein were not statistically significant. Fifteen cows fed thyroprotein from parturition averaged 6,516kg milk (308-day, mature equivalent) compared to 6,703kg for 18 control cows. Both control and thyroprotein-fed cows increased mature equivalent lactation yields for two or three successive years.Thyroprotein feeding resulted in marked reductions in body weight, barrel circumference, and body condition and marked increases in heart rates, respiration rates, and rectal temperatures. Cows and first-calf heifers receiving thyroprotein required more services per conception (P<0.05) and had longer calving intervals (P<0.01) than control cows. No significant differences were noted in other health related data between the thyroprotein-fed and control animals.