Reproductive development of male lambs born to undernourished mothers supplemented or not with concentrate during gestation

Abstract

Southern Patagonia offers harsh environmental and nutritional conditions for sheep pregnancy, which may compromise the fetal and postnatal development of lambs. The aim of the study was to compare the sexual behavior and attractiveness, and semen production and quality during the first year of life of ram lambs born to undernourished mothers grazing on natural pastures, supplemented or not with a concentrate. The study was performed under extensive Patagonian conditions, and a supplement was provided from day 44 of gestation until lambing. Twelve ram lambs born to supplemented ewes (group Sup) and 12 born to control underfed ewes (group Con) were used. Both groups of male lambs remained in a common paddock before and after weaning at 4 months-old. Sexual behavior and attractiveness, and semen production and quality of ram lambs were evaluated when they were 6 and 12 months-old. Sup lambs were heavier than Con at birth, and tended to maintain this difference when they were 4 mo-old; afterward, this difference disappeared. At 6 months-old, Con ram lambs displayed greater sexual activity when individually exposed to an estrous ewe, as well as a trend to a greater sperm concentration. Differences between groups in sexual behavior decreased at 12 months-old, and no differences were detected in seminal traits. In conclusion, supplementation of undernourished pregnant ewes with concentrate from mid-pregnancy until lambing slightly impacted the progeny reproductive performance when they were 6 months-old, an effect that was attenuated at 12 months-old. The effects of the nutritional status of pregnant ewes on the reproductive development of the offspring likely were compensated by a greater growth rate during early life before puberty.