Influence of dietary intake and lasalocid on serum hormones and metabolites and visceral organ growth and morphology in wether lambs

Twenty-four black face, crossbred wether lambs (32.4 +/- 6.1 kg) were assig ned to one of four treatments arranged in a 2 x 2 factorial. Individually p enned wethers were fed a pelleted total mixed diet at low intake (LI; 60% o f ad libitum) or high intake (HI; 95% of ad libitum); diets contained eithe r low lasalocid (LL; 0 mg per lamb daily) or high lasalocid (HL; 40 mg per lamb daily). Measurements of serum hormones and metabolites were taken duri ng two S-day collection periods following a 14-day adjustment to treatments . After 42-45 day on treatments, wethers were slaughtered and weight (wt) o f liver and intestinal segments were recorded and tissues subsampled. Serum insulin and glucose concentrations were increased (p < 0.10) in lambs on H I compared with those on LI. Total ruminal VFA concentration (millimolar) w as increased (p < 0.10) with greater for HI vs LI. Compared with LI, HI had greater (p < 0.10) final BW, eviscerated BW (EBW), and total visceral wt; colon fresh, dry, and dry fat-free wt; cecum dry wt; liver fresh wt, dry wt and dry fat-free wt, liver RNA : DNA ratio, RNA content, and protein conte nt; and duodenum RNA content. Liver DNA concentration was decreased (p < 0. 10) in HI vs LI. Neither labeling index nor morphology of intestinal segmen ts were influenced (p > 0.10) by intake or lasalocid. Lasalocid had little influence on metabolic hormones or growth and development of visceral organ s. These data indicate that high intake increased serum insulin and glucose concentrations, liver wt and cell size. (C) 2000 Elsevier Science B.V. All rights reserved.