Protein digestibility of ruminant feeds by the three-step procedure

Abstract

The three-step procedure was used to evaluate ruminal degradable and undegradable protein of soybean meal (SM), sorghum grain (SG), cottonseed (CT), corn silage (CS) and tomato byproduct (TBP). Feeds were initially incubated in rumen of fistulated steers for 16 h. After that, 15mg of nitrogen were submitted to acid pepsin, for one hour, and alkaline pepsin for 24 h. The SM and CT showed 97 and 93% total protein digestibility, which is the major portion available in the rumen (94 and 92% respectively). The SG protein showed the lowest digestibility (73%) followed by TBP and CS that had 72 and 73% total protein digestibility. It was concluded that SM and CT showed high protein digestibility, however the most portion was degraded in the rumen and that besides the high lignin proportion, the TBP was the one which supplied more available intestinal protein.