INTAKE AND RUMINAL FERMENTATION BY BEEF STEERS CONSUMING PRAIRIE HAY WITH SUPPLEMENTS CONTAINING COMBINATIONS OF CORN, SOYBEAN HULLS, SOYBEAN-MEAL AND UREA

Twelve ruminally cannulated beef steers (408 +/- 17.2 and 418 +/- 15.4 hg initial and final body weight, respectively) fed prairie hay were used to evaluate the effects of substituting soybean hulls for one-hal f the corn in a urea-based protein supplement on forage intake and rum inal fermentation during two periods. Treatments (three steers treatme nt(-1)) were no supplement (CON),corn plus soybean meal (CS), CS plus urea (CU) and CU plus soybean hulls (SU). Urea provided approximately 35% of the total crude protein (CP) for the CU and SU supplements. Sup plements were fed at approximately 145% of maintenance CP requirements . Periods consisted of 14 d for adaptation to the supplement and 7 d f or intake measurements. On d 22 of each period, ruminal samples were c ollected at 0, 0.5, 1, 2 and 4 h after supplementation. Following the 4-h sample, ruminal contents were removed for determination. of dry ma tter (DM) fill and indigestible acid detergent fiber (IADF) passage an d fill. Forage and total DM intake did not differ (P>0.10) among treat ments. Passage rate of IADF was greater (P<0.10) for CS than for the a verage of CU and SU. Ruminal DM fill and IADF fill were greater (P<0.1 0) for the average of CU and SU than for CS. Ruminal pH was not affect ed (P>0.10) by treatments. At 0.5 h after supplementation (treatment x sampling time, P<0.10) acetate was increased (P<0.05) for CS vs. the average of Cv and SU. Across sampling times, propionate was increased and the acetate:propionate ratio was decreased (P<0.10) for the averag e of Cv and SU vs. CS. Ruminal ammonia concentration was increased (P< 0.10) by supplements compared with CON at all sampling times. Ammonia concentration was greater (P<0.01) for the average of Cv and SU than f or CS at 0.5, 1 and 2 h after supplementation, and increased (P<0.10) for Sv us. CU at 0.5 h. Results suggest that soybean hulls can replace corn in urea-based protein supplements without adversely affecting in take or ruminal fermentation, albeit no benefits were noted from the s ubstitution.