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Abstract
Two finishing trials and a metabolism trial were conducted to evaluate level of ruminally degradable N in finishing diets on animal performance, carcass characteristics and ruminal metabolism. Supplementing steers with either.88, 1.34, or 1.96% urea resulted in no difference in dry matter intake, daily gain, or feed efficiency. Steers fed diets supplemented with urea were 5.4% more efficient and gained 6.6% faster than steers receiving no supplemental urea. Metabolizable protein supplied in all diets exceeded the steer's requirements. However, diets containing no urea were deficient in ruminally degradable N. In the metabolism trial, N intake and ruminal ammonia N concentration increased linearly with level of urea supplementation. Diets containing no urea were deficient in ruminal ammonia N. Results from this study indicate dry-rolled corn finishing diets are deficient in ruminally degradable N. Supplementing these diets with an inexpensive source of ruminally degradable N improved animal performance. However, supplementation with urea above.88% was not beneficial. In addition, two finishing trials and a metabolism trial were conducted to evaluate the effect of forage source and forage particle size in finishing diets on animal performance, carcass characteristics and ruminal metabolism. In finishing Trial 1, steers fed diets containing forage had greater DMI than steers fed all-concentrate diets. Steers fed alfalfa diets gained faster with a greater concentrate efficiency (ingredients minus forage) compared with steers fed either all-concentrate diets or diets containing wheat straw. In finishing Trial 2, altering alfalfa particle size had no effect on any performance or carcass measurement. In the metabolism trial, steers fed straw diets spent more time chewing and tended to have higher ruminal pH, lower total VFA concentration, and higher acetate to propionate ratios compared with other treatments. In conclusion, altering alfalfa hay or wheat straw particle size had no effect on finishing cattle performance or ruminal metabolism. However, daily gain and feed efficiency in steers fed diets containing either alfalfa hay or wheat straw was not similar.
