Influence of dietary roughage level on reproductive rate in ewe lambs.

Crossbred ewe lambs initially weighing approximately 90 lb (41 kg) were fed rations varying in roughage level prior to breeding to examine the influence of level of dietary energy upon subsequent reproductive performance when bred as lambs. In the two trials conducted over a 2-year period 200 spring-born Iambs were placed in four lots of 25 lambs each year and received rations containing 12% crude protein and ground mixed hay at 10, 30, 50 or 70% of the diet. Average initial weights were 100.6 + 14.8 and 83.8 + 11.2 lb (45.7 + 6.7 and 38.1 + 5.1 kg), respectively. Average daily gains during the first trial of 56 days were .46, .31, .24 and .09 lb (.20, .14, .11 and .04 kg), respectively, for diets containing 10, 30, 50 and 70% roughage. During the second trial of 99 days average daily gains were .42, .40, .24 and .04 lb (.19, .18, .11 and .02 kg), respectively. At the end of each feeding period five lambs from each t reatment were slaughtered and carcass measurements collected. Weight and fat parameters were found to decrease (P<.05) with increasing dietary roughage level. The remaining ewes were pooled, exposed to rams for 40 days, and checked for pregnancy using echo analysis during the first 50 days of pregnancy. Pregnancy detection was accurate 75% of the time. Reproductive performance did