Effects of dietary energy density on feed intake, body weight gain and carcass chemical composition of Omani growing lambs

Forty male Omani lambs were used in a feeding trial to study the effects of feeding diets containing various levels of metabolizable energy (ME) on growth and carcass composition. Ten lambs were selected randomly and slaughtered at the start of the trial to provide information on initial carcass composition. Thirty lambs were divided randomly into three groups and fed three diets varying in ME concentration (low, medium and high) from weaning (at average 76 days) until slaughter at the mean weight of 30 kg. Digestibility of dry matter (DM) was 66.9, 68.7 and 73.9% for low, medium and high energy diets, respectively. Apparent gross energy digestibility was 66.8, 67.2 and 73.3% corresponding to dietary concentrations of 12.2, 12.6 and 13.9 MJ of DE/kg for low, medium and high energy diets, respectively. Daily DM intake ranged between 3.12 and 3.73 % of body weight (BW) which was equivalent to 76.5–97.5 g/kg 0.75 or 0.738–1.142 MJ ME/kg 0.75. Daily BW gain increased ( P < 0.001) with increasing ME density with a maximum of 154 g/day observed in lambs on high energy diet during the last 4 weeks of the experiment. Feed conversion ratio (FCR), i.e., kg feed/kg BW, improved with increasing ME density ( P < 0.001). Sheep fed high energy diet had heavier BW ( P < 0.01), empty BW weight ( P < 0.001), carcass weight ( P < 0.01) higher dressing percentage ( P < 0.05) but lower gut content ( P < 0.001) than lambs fed medium and low energy diets. Sheep slaughtered at the end had lower water, protein but higher carcass and non-carcass chemical fat than sheep slaughtered at the start of the experiment. This study indicated that meat production from sheep in Oman will be improved in form of higher BW gains and better carcass composition by increasing energy levels in the diet.