ASSOCIATIONS BETWEEN MILK-PROTEIN PRODUCTION AND REPRODUCTION, HEALTH, AND CULLING

Associations between protein production and individual-cow reproductiv e performance, health, and culling were investigated in a 2-year obser vational study involving a convenience sample of 75 Ontario, 5 Alberta , and 3 Nova Scotia dairy farms. Protein production was defined by 305 -day lactation protein yields and by estimated breeding values for pro tein yield. After controlling for the level of milk production, herd, parity, breed, and season of calving, there were no significant associ ations between either measure of protein production and days open or d ays to first breeding. The only associations between protein productio n and disease were small positive associations between the estimated b reeding value for protein yield and cystic ovaries and mean lactation somatic cell count. The risk of culling, after controlling for the lev el of milk production, was negatively associated with previous-lactati on 305-day protein yield for parity three animals only. The estimated breeding value for protein yield had a small negative association with the overall risk of culling, although the associations were not signi ficant for individual lactations. (C) 1998 Elsevier Science B.V.