Dietary protein intake during the oestrous cycle does not alter the ovulation rate in gilts

The effect of protein intake on ovulation rate was investigated in cross-bred gilts. On Day 14 of the third oestrous cycle, luteolysis was induced by injection of an analogue of prostaglandin F(2alpha). The ovulation rate was recorded when gilts were killed on Day 27. In the first experiment, nutritional treatment was applied from Day 14 to Day 27. Gilts were fed diets providing the same amount of digestible energy, but containing either a low, medium or high amount of dietary protein. Protein restriction linearly decreased plasma concentrations of urea (P < 0.001) and had no effect on plasma concentrations of insulin-like growth factor-I and leptin measured at Day 27 (P > 0.1). Protein restriction did not influence ovulation rate (mean (+/- s.e.m.) 17.0 +/- 0.4; P > 0.1). In the second experiment, the nutritional treatment was applied from Day 5 until Day 27. Gilts received the same amount of digestible energy and either a low or a high amount of protein, as in Experiment 1. A third group of gilts received the high amount of protein and also more digestible energy. The ovulation rate did not differ between the three groups of gilts. These data indicate no effect of short-term dietary protein restriction on ovulation rate in cyclic gilts.