Effects of grain level on lamb performance, ruminal metabolism and leptin mRNA expression in perirenal adipose tissue

The effects of four different grain composition diets of finishing lambs on lamb performance, dry matter (DM) digestibility, rumen fermentation and leptin mRNA expression were evaluated. Thirty-two Pelibuey lambs (25.35 ± 4.73 kg bodyweight) were used in a completely randomised experiment in which lambs were fed diets that contained 30%, 45%, 60% or 75% grain (DM basis). The results indicated that increasing the grain level improved the average daily weight gain, hot carcass weight, DM digestibility and feed conversion linearly (P < 0.01); however, feed intake was not affected. Ruminal pH decreased linearly as the grain content was increased (P < 0.01). Ruminal propionate concentration increased and acetate concentration declined with increased grain content (P < 0.01). Leptin mRNA expression in perirenal adipose tissue increased linearly (P < 0.05) as grain content increased. Based on these results, we conclude that increasing grain level in the diets of finishing feedlot lambs improved weight gain and feed efficiency; however, because weight gain and feed efficiency were similar at the higher grain levels, our data suggest including 60% grain in lamb finishing rations.