Using Rumen Degradation Model to Evaluate Microbial Protein Yield and Intestinal Digestion of Grains in Cattle

摘要

Ruminal degradation and kinetic parameters are usually obtained using the polyester (nylon) bag technique. Rumen degradation data were used to estimate yields of rumen microbial protein (RMP) and total protein digestion in the intestines (PDI). The content of organic matter (OM) and crude protein (CP) disappearing from nylon bags were expressed as a proportion of the original sample content and the results fitted to the exponential model, P = A + B(l - e~(-k)_(d~t)), total yield (g/kg of dry matter (DM)) of RMP was estimated as: RMP = (FOM/1000) x 150. The yield (g/kg DM) of RMP from fermentable CP (FCP) was estimated as: RMPCP = (FCP/1000) x 75.The yield (g/kg DM) of RMP from fermentable carbohydrate (FCHO) was estimated as: RMP-CHO = RMP -RMPCP.The yield (g/kg DM) of RMP digested in the intestines was estimated as: RMPI = RMP x 0.85, assuming that RMP is digested in the intestines with an efficiency of 85%. The OM and CP degradability constants (A, B, k_d and A + B) of two grains treated with the highest temperature (140 deg C) were the lowest, while full-fat soybean (FFS) was higher (P < 0.05) than that of sunflower seeds (SS).The effective degradability of OM and CP increased with increasing temperature. The yields of RMP from FCHO, FCP andtotal RMP of FFS were significantly higher (P < 0.05) than those of SS. Nevertheless, yields of RMP from grains decreased with increasing temperature. Estimated rumen undegradable protein (RUP) increased with increasing temperature of grains. However, PDI declined at high temperatures. At 140 deg C total PDI was the lowest. The estimated values from this study could be used to improve ration formulation, efficiency utilization of feeds and nutritive value of grains. Available supplements should be evaluated using ruminal protein degradation information, estimates of support for microbial protein synthesis and intestinal digestibility.