Growth and carcass characteristics of beef steers fed silage and different levels of energy with or without protein supplementation.

Fifty-six large-framed crossbred steers averaging 227 kg were used in an experiment including a growing period (24 wk) and a finishing period ending when the steers had approximately 4 to 10 mm of fat thickness (Canadian grade A1). Steers were individually fed and assigned to a completely randomized design with seven treatments for the growing period. From the end of the growing period until slaughter, all steers received the same basal diet. Half of the steers from each treatment used in the growing period received a supplement containing protein and the other half a supplement containing protein and fat. Treatments during the growing phase consisted of 1) timothy silage alone or mixed (on a DM basis) with 2) 7.5% molasses, 3) 15% molasses, 4) 7.5% canola meal, 5) 5.5% canola meal and 7.5% molasses, 6) 3.6% canola meal and 15% molasses, or 7) 15% canola meal. The total N intake from supplements 2, 5, or 6 was similar. Compared with silage fed alone, canola meal supplementation increased (P < .05) ADG, whereas molasses had no effect. Combining molasses and canola meal did not improve ADG compared with feeding only canola meal on an isonitrogenous basis. Canola meal supplementation compared with feeding only silage during the growing phase reduced (P < .05) days on feed, and molasses tended (P = .059) to reduce it. Carcass data were generally similar among treatments.(ABSTRACT TRUNCATED AT 250 WORDS)