EFFECTS OF DIETARY ENERGY-INTAKE AND PROTEIN-CONCENTRATION ON PERFORMANCE AND VISCERAL ORGAN MASS IN LAMBS

Eighty-eight early-weaned Hampshire x Targhee crossbred lambs (initial BW 23 +/- 3.9 kg) were used in a 2 x 2 factorial design experiment to determine the effects of DM and CP intake on lamb performance and wei ght and accretion rates of visceral organs during two periods of growt h, divided at 36 kg live weight. There were 10 lambs per replicate and two replicate pens per treatment. Dry matter intake was 100 or 85% of ad libitum, and protein intake was 100 (normal) or 125% (high) of the calculated NRC (1985) requirement. Over both periods, lambs allowed a d libitum access to feed had greater (P < .05) ADG, rumen/reticulum, l arge intestine, and liver weights and faster accretion rates than lamb s fed at 85% of ad libitum; however, there were no differences (P = .8 7) in feed efficiency. For the total trial, lambs fed high protein had greater (P < .01) DMI, ADG, liver and kidney weight and accretion rat es, and increased (P < .01) feed efficiency during period 1 compared w ith lambs fed normal protein concentrations. Diets containing high con centrations of dietary protein resulted in greater DMI and ADG through out the feeding period compared with diets formulated at NRC (1985) re commended concentrations, indicating that (1985) protein recommendatio ns may limit performance. Restricted feeding resulted in reduced visce ral organ mass compared with offering feed for ad libitum consumption. Restricted feeding increased efficiency of feed utilization for gain, in part, through reductions in visceral organ mass.