Effect of Monensin and Live Yeast Supplementation on Growth Performance, Nutrient Digestibility, Carcass Characteristics and Ruminal Fermentation Parameters in Lambs Fed Steam-Flaked Corn-Based Diets * (Report‪)‬

ABSTRACT : In performance, digestibility and slaughter trials, a total of forty five male weaned lambs were used to examine the effects of monensin and live yeast supplementations on growth performance, nutrient digestibility, carcass characteristics and ruminal fermentation parameters when the lambs were fed steam-flaked corn-based diets. Animals were allotted to one of three treatment diets in a completely randomized design. The three treatment diets were: (1) basal diet (CON) with steam-flaked corn as a sole grain source, (2) basal diet supplemented with monensin (MO), and (3) basal diet supplemented with live yeast (LY). Total average daily intake (ADI) was unaffected by MO and LY supplementations. LY supplementation increased (p0.05) average daily gain (ADG) by 13.1% compared with the CON diet. Both MO and LY supplementations resulted in a significant improvement (p0.05) of feed efficiency over the CON diet (4.47, 4.68 vs. 5.05). Hemicellulose digestibility was higher (p0.05) for lambs in the LY supplementation group (62.4%) as compared with the CON group (55.7%), but no differences were observed in digestibilities of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF). All carcass traits were not influenced by dietary supplementations. Ruminal pH in lambs fed the LY supplemental diet was more stable than that with the CON diet (6.57 vs. 6.17). Neither MO nor LY supplementation influenced the concentration of ruminal ammonia-N and total volatile fatty acid (VFA), and molar percentages of individual VFA. Plasma urea-N concentration was decreased (p0.05) by MO and LY supplementations, while plasma [beta]-hydroxybutyrate (BHBA), glucose and other blood parameters were unaffected. In conclusion, while both MO and LY supplementations had a positive impact on feed efficiency and LY supplementation stabilized ruminal pH and improved fiber utilization, none of the supplements had the capacity to significantly enhance the carcass characteristics. (Key Words : Weaned Lambs, Monensin, Live Yeast, Growth, Digestibility, Carcass Characteristics) INTRODUCTION