INFLUENCE OF PROTEIN-LEVELS AND NALOXONE ON RUMINAL FERMENTATION, SERUM HORMONES AND METABOLITES IN LAMBS FED OAT HAY OR BARLEY STRAW

Effects of increasing levels of supplemental protein and naloxone injections on ruminal fermentation, serum hormones and metabolites in lambs were studied in two trials. Supplement x naloxone and sampling time x treatment interactions (Trial 1) for all variables were not significant. Serum growth hormone (GH) decreased (P < 0.05) with supplemental protein (4.4 for supplemented lambs vs. 7.1 ng/ml for controls). Serum insulin (INS) was increased (P < 0.01) by supplementation, but naloxone did not affect GH or INS. Supplementation elevated (P < 0.01) serum urea N and reduced (P < 0.01) serum free fatty acid (FFA) concentrations but did not affect serum glucose. Naloxone injections did not affect (P > 0.10) concentrations of serum metabolites. Protein supplementation increased (P < 0.04) ruminal ammonia concentrations (Trial 2), but ruminal pH did not change as protein level increased. Ruminal proportions of propionate (P < 0.03) responded cubically to supplemental protein level. Serum GH changed quadratically (P < 0.01) with increasing protein, and serum INS rose linearly (P < 0.05) with protein level. Serum glucose and FFA were not affected by supplemental protein (Trial 2). Serum urea N increased (P < 0.04) with protein, especially when protein was fed at 125 and 150% of requirements. Supplemental protein has a positive effect on ruminal fermentation of low-quality roughage by sheep and alters metabolic hormone profiles in a manner reflecting an improved protein and energy status.