The influence of pre- and post-mating protein supplementation on reproductive performance in ewes maintained on rangeland

The effect of short-term changes in level of protein supplementation during pre- and post-mating on non-return rate, lambing rate and litter size was investigated in ewes grazing on rangeland during early autumn. Groups of ewes were fed diets providing either 58 g (low, L) or 113 g (high, H) crude protein per day per ewe grazing on rangeland. Diets were calculated on a dry matter bases to provide 0.7 and 1.3 times protein requirements for maintenance. Following the first detected estrus, a total of 130 adult ewes were allocated into either L (n = 67) or H (n = 63) treatment until next estrous (pre-mating). At the second estrus, the ewes were mated, and again randomly allocated to either the L or H allowance until day 15 (post-mating; mating = day 0). Hence, there were four nutrition treatments; LL (n = 35), LH (n = 32), HL (n = 32) and HH (n = 31). Non-return rate, lambing rate tended to be higher in ewes fed the LH diet (0.88 and 81.3%) than the HL diet (0.69; P < 0.07 and 59.4%; P < 0.06). A similar effect of the LH diet (81.3%) was observed for lambing rate compared to the LL diet (60.0%; P < 0.06). The mean litter size and fecundity were higher in the LH (1.31 and 1.06) compared to the LL (1.09 and 0.66; P < 0.05). The mean litter size of ewes in HL (1.32) and HH (1.42) diets was higher than those in the LL (1.09; P < 0.05) diet. It was concluded that short-term (15–17 days) changes in level of protein supplementation especially post-mating can have a beneficial effect on non-return rate and lambing rate to first estrus and litter size in ewes grazed on rangeland. © 2005 Elsevier B.V. All rights reserved.