SUPPLEMENTAL CRACKED CORN OR WHEAT BRAN FOR STEERS GRAZING ENDOPHYTE-FREE FESCUE PASTURE - EFFECTS ON LIVE WEIGHT-GAIN, NUTRIENT QUALITY, FORAGE INTAKE, PARTICULATE AND FLUID KINETICS, RUMINAL FERMENTATION, AND DIGESTION

Two experiments were conducted with beef steers (Exp. 1, average BW of 580 kg; Exp. 2, average BW of 247 kg) to evaluate the use of no suppl ements (CON) or daily supplementation with (OM basis) .34% of BW of cr acked corn (CORN), .34% of BW of wheat bran (WBBW), or .48% of BW of w heat bran (WBISO; calculated to be isocaloric to CORN) on digestive re sponses (Exp. 1) and live weight gain (Exp. 2). In Exp. 1, type of sup plement did not affect (P > .10) the dietary fiber or N constituents, but in vitro OM disappearance of the forage differed (P < .10) with su pplementation and type of supplement fed. Supplemented steers consumed less (P < .05) forage and total OM. Particulate passage, fluid passag e, and ruminal pH were not affected (P > .10) by supplementation. Rumi nal NH3 N concentration showed (P < .05) a treatment x sampling time i nteraction and, in general, WBBW and WBISO steers had greater ruminal NH3 N than CORN and CON steers. Total VFA concentrations and molar pro portions of propionate were lower (P < .10) in CON steers than in supp lemented steers; no differences were noted (P > .10) among supplemente d steers. Molar proportions of acetate were lower (P .01) in supplemen ted steers than in CON steers and were greater (P = .03) in WBBW steer s than in WBISO steers. Butyrate molar proportions were lower (P < .05 ) in CON steers than in supplemented steers and differed (P < .10) wit h type and quantity of supplement supplied. In situ forage NDF disappe arance at 6, 9, and 24 h after feeding and rate of disappearance were greater (P < .05) in CON steers than in supplemented steers. In Exp. 2 , CON steers weighed less (P = .01) than supplemented steers, CORN ste ers weighed more (P = .08) than wheat bran-supplemented steers, and WB ISO steers weighed more (P = .02) than WBBW steers; ADG for 90 d follo wed a similar response. Results suggest that supplementation of wheat bran rather than corn did not seem to stop the reduction in forage int ake or OM digestion associated with corn supplementation.