EFFECT OF CRUDE PROTEIN ON REPRODUCTIVE EFFICIENCY, SERUM TOTAL PROTEIN, AND ALBUMIN IN THE HIGH-PRODUCING DAIRY COW

Forty-five high-producing dairy cows were assigned randomly in equal numbers and fed one of three isocaloric rations of 12.7, 16.3, or 19.3% crude protein starting at 4 days postpartum and continuing for 91 days. The 19.3% group had fewer days to first observed estrus (27 days) than the 16.3 and 12.7% groups (41 days). The 12.7 and 16.3% groups had fewer services per conception (1.67) than the 19.3% group (2.47). The 12.7% group had fewer days open than the 16.3 and 19.3% groups (69, 96, and 106 days). The relationship between days open, dietary protein intake, and services per conception was linear in the three groups combined. In the 19.3% group, days to first ovulation were correlated positively with average fat corrected milk (.62) while days to first ovulation were not correlated significantly in the other groups. Total protein and albumin in serum did not differ between groups. Albumin in serum increased quadratically over the 14 wk trial while total protein in serum increased linearly the 1st 4 wk and then plateaued. Increased crude protein (12.7 to 19.3%) had a negative influence on reproductive parameters. © 1979, American Dairy Science Association. All rights reserved.