IN SITU DRY MATTER AND PROTEIN DEGRADATION OF VARIOUS PROTEIN SOURCES IN DAIRY CATTLE

Abstract

In situ dry matter and protein degradation of various protein sources in the rumen of Holstein steers and cows were studied. The effective degradability of each feed protein was estimated from nonlinear parameters and an assumed constant outflow rate of solids. Protein sources tested were soybean meal (SBM), canola meal (CM) and dehydrated alfalfa meal (Dehy), in exp. 1, and fish meal (FM), CM, CM treated with formalin (FCM) and whole pig blood (BCM) in exp. 2. Nitrogen disappearance, estimated from nylon bags suspended in the rumen, of SBM was less than that of CM; disappearance of Dehy was less than that observed for both oil seed meals. The disappearance of FM was significantly less than all other feed proteins. Formalin treatment of CM was very effective in reducing both dry matter and nitrogen disappearance from the bags, but blood treatment was not effective. Protein degradability estimated from disappearance data was 53.6, 65.8, 41.4, 28.9, 65.5, 22.2, 71.2 and 70.8% for SBM, CM, Dehy, FM, CM, FCM, 30% BCM and 50% BCM, respectively. Key words: In situ, dry matter degradation, nylon bags, rumen, protein degradation, cattle