Effect of Crude Protein on Reproductive Efficiency, Serum Total Protein, and Albumin in the High-Producing Dairy Cow

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Abstract
High-producing dairy cows (45) were assigned randomly in equal numbers and fed 1 of 3 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 1st observed estrus (27 days) than the 16.3 and 12.7% groups (41 days). The 12.7 and 16.3% groups had fewer services/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/conception was linear in the 3 groups combined. In the 19.3% group, days to 1st ovulation were correlated positively with average fat corrected milk (0.62) while days to 1st 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 four wk and then plateaued. Increased crude protein (12.7-19.3%) had a negative influence on reproductive parameters.