Effects of restricted feeding on growth performance and carcass composition of lambs

Fifty-eight crossbred lambs (26 kg BW) with moderate growth potential were used in a completely randomized design experiment to determine the effects of restricted feeding of all-concentrate diets on performance and carcass composition. Feeding levels studied were 100, 85, and 70% of ad libitum intake. Diets that were restricted-fed were formulated to have increased nutrient concentrations to provide equal daily intakes of protein, vitamins, and minerals among DM intake levels. Lambs were fed to a final weight that would yield carcasses of equal weight (24 kg). Average daily gain was reduced linearly (P < .02) and days on feed were increased linearly (P < .02) because of restricted feeding. Feed efficiency, however, was not affected by intake level. The quantity of separable lean tissue within carcass sides was increased (P < .05) with restricted feeding. Total separable fat within the side was reduced (P < .05) in an amount equal to the increase in lean tissue accretion. Chemical analysis of the carcass side showed a decrease (P < .05) in fat percentage and a corresponding increase (P < .05) in water percentage because of restricted feeding. Daily accretion rates of lean and bone tissue were not affected by restricted feeding; however, fat accretion was decreased linearly with decreasing feeding levels. Separable lean tissue within the primal cuts was generally increased with decreasing intakes, which led to a corresponding decrease in separable fat. Restricted feeding strategies can lead to the production of leaner carcasses. Reductions in fat content occur in the subcutaneous, seam, and mesenteric depot sites, but intramuscular fat content of consumable product also is reduced.