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1529
Effect of live yeast fed to natural-program beef steers during the finishing phase
Growth performance, carcass characteristics, nutrient digestibility, and feeding behavior were evaluated in natural-program beef cattle fed steam-flaked corn-based finishing diets with 3 inclusion levels of live yeast (ABVista Inc., UK: 0, 25, and 50 g/steer daily). Steers (n = 144; 341 ± 20 kg) were blocked by BW and assigned to treatments in a randomized complete block experimental design. The natural program did not include the use of implants, ionophores, and antibiotics. Live yeast was included in a premix (cottonseed meal carrier) at 1% of the diet (DM basis). Data were analyzed using the GLIMMIX procedure of SAS with pen used as the experimental unit. Feed efficiency tended to be improved (quadratic, P = 0.08) between d 0 to 183, with steers fed 25 g/d of live yeast having a 4.3% greater G:F than the average of other treatments. Linear increases in premium Choice (P < 0.01) and Choice (P = 0.05) carcasses were observed as live yeast increased in the diet. Total tract nutrient digestibility increased (quadratic, P < 0.01) as live yeast increased, with steers fed 25 g/d having greater digestible DM (5.4 %), organic matter (4.8 %), NDF (22.1 %), ADF (19.9 %), hemicellulose (22.7 %), crude protein (6.2 %), and ether extract (2.5 %) than the average of steers in the other treatments. Rumination (11%), eating time (8%), and chewing activity (20%) were not affected by treatments (% of 24 h evaluation). Live yeast included at 25 g/d in the finishing diet of natural-program beef steers improved dietary nutrient digestibility (except starch), carcass quality grade, and tended to improve gain efficiency, without affecting feeding behavior.
Keywords: digestibility, live yeast, natural program