Effects of Dietary Protein Source and Energy Level on In Situ Nitrogen Disappearance of Various Protein Sources

Abstract

Effects of dietary energy level and dietary protein source on in situ N disappearance of various protein sources were determined. In Exp. 1, effects of dietary corn treatment and energy level were determined for rumen pH and in situ N disappearance of casein (CN), soybean meal (SBM), blood meal (BM), meat and bone meal (MBM), pelleted dehydrated alfalfa (DA) and corn gluten meal (CGM). Three percent NaOH-treated corn (NaOH-C) or high moisture corn (HMC) was fed to four rumen fistulated cows at 20, 40, 60 and 80% of the diet. Mean rumen pH averaged over time and dietary energy level was greater (P<.01) for cows fed NaOH-C than for those fed HMC. Nitrogen disappearance of CN, SBM and DA tended to be affected more by corn treacment and level than did N disappearances of BM, MBM and CGM. The effect of dietary protein supplement (urea, SBM, BM, MBM and DA) on in situ N disappearance of SBM, BM, MBM and DA was measured in Exp. 2. A dietary protein supplement × incubated protein source interaction existed (P<.01) for in situ N disappearance at 12 h, suggesting that in situ N disappearance of protein sources may vary with dietary protein supplement.