The effect of forage source and particle size on finishing yearling steer performance and ruminal metabolism

Two finishing trials and a metabolism trial were conducted to evaluate the effect of forage source and particle size in dry-rolled corn finishing diet s. In Exp. 1, 224 crossbred yearling steers (BW = 342 +/- 11 kg) were used in a randomized complete block design consisting of seven treatments. Treat ments were an all-concentrate diet or diets containing equal NDF levels pro vided by alfalfa hay or wheat straw (three treatments each) with each forag e source ground to pass through a .95-, 7.6-, or 12.7-cm screen. Steers fed diets containing forage had greater (P < .05) DMI than steers fed an all-c oncentrate diet. Steers fed alfalfa diets gained faster (P < .05) with a gr eater (P < .05) concentrate efficiency than steers fed either all-concentra te or straw diets. In Exp. 2, 120 crossbred yearling steers (BW = 307 +/- 2 kg) were used in a completely randomized design and fed dry-rolled corn di ets containing 10% alfalfa ground to pass through either a .95- or 7.6-cm s creen. Alfalfa particle size had no effect on performance or carcass measur ements. In Exp. 3, six ruminally fistulated steers (BW = 508 +/- 34 kg) wer e used ina 6 x 6 Latin square design and fedan all-concentrate diet or diet s containing equal NDF levels provided by alfalfa hay, wheat straw, or grou nd corncobs with alfalfa and straw ground to pass through, either a 2.54- o r 12.7-cm screen. Steers fed straw diets spent more time (P < .10) chewing than those receiving the other diets. In conclusion, forage particle size h ad no effect on finishing cattle performance or ruminal metabolism data. Ho wever, cattle consuming different forage sources in dry-rolled corn finishi ng diets may not respond similarly in animal performance.