UTILIZATION OF SUPPLEMENTAL BYPASS PROTEIN IN SUPPLEMENTS CONTAINING BLOOD MEAL FED TO GESTATING AND GROWING CATTLE MAINTAINED ON MATURE NATIVE FORAGE

The utilization of bypass protein in supplements fed on winter range was investigated. An in situ study was conducted to evaluate the rate of ruminal crude protein (CP) degradation of; 44.5% CP soybean meal (SBM), 18.6% CP dehydrated alfalfa (DA), 29.7% CP brewers dried grains (BDG); 86.2% CP blood meal (BM) and 4.7% CP native winter forage (NF) collected via esophagael fistula. The rate of degradation of slowly degraded protein (percent per hour) and the equation that best fitted protein degradation (x = time) were: 13.9%/hr, y = 4.49 x (\u27-1.52); 5.4%/hr, y = 1.60 x (\u27=.67); 1.4%/hr, y = 1.64 x (\u27-.41); .4%/hr, ln y = 4.49 -.004; and .7%/hr, y = .81 x (\u27-.16), for SBM, DA, BDG, BM, and NF, respectively. Two metabolism studies were conducted to investigate nitrogen utilization in supplements when fed to steers consuming mature native forage. The nitrogen sources of the supplements were: 100% soybean meal (SMB), 10% corn-40%-50% area (SBM-U), 14% corn-36% blood meal-50% urea (BM-U) and 15% corn-85% urea (U). Steers feed SBM, BM-U or SBM-U had similar (P \u3e .05) rumen microbial protein production and non-ammonia nitrogen-flow. Nitrogen balance and dry matter digestibility were higher (P \u3c .05) for steers fed SBM and BM-U supplements than those fed SBM-U supplements. Bypass protein values were calculated to be 16.5 and 21.5% for soybean meal nitrogen in the soybean meal-urea and soybean meal supplements, respectively. The value for blood meal was 54.2%. Three trials were conducted to compare performance of cattle grazing native winter range fed crude protein supplements. Forty-five gestating crossbred cows (15 per supplement) were fed one of the supplements. Cows fed SBM lost less weight (P \u3c .017) than those consuming BM-U or SBM-U. In the second study 27 crossbred calves were fed one of three supplements. Steers fed SBM had a higher (P \u3c .016) average daily gain than those fed either BM-U or SBM-U. A third study was a 3 x 4 factorial arrangement (4 supplements and 3 age groups of gestating females). Three supplements were similar to those used the previous year and the fourth was composed of the following nitrogen sources: 4% corn - 14% dried whey - 32% soybean meal - 50% urea. Weight gains were not different (P \u3e .05) across supplement or age groups