Rumen fermentation and microbial yield of high- or low-protein diets containing ground soybean seeds or homemade rapeseed expellers evaluated with RUSITEC

Abstract

This experiment aimed to compare diets containing two crude protein (CP) concentrations [147 or 109 g kg-1 in dry matter (DM)] and two protein sources containing ground soybean seed (GSS) or rapeseed expeller (RSE). Diets were compared in terms of digestibility, volatile fatty acids (VFA) and ammonia concentrations, and N flows, using rumen simulation fermenters (RUSITEC). Home-made RSE (CP=287 g kg-1 dry matter and ether extract=199 g kg-1 DM) was produced using equipment adopted by small farms. Reduction of dietary CP content did not affect digestibility, except for a reduction of N apparent digestibility (P<0.01), but increased efficiency of N utilization (P-0.001) without affecting microbial N production (P=0.82). Total VFA concentration was not (P=0.56) influenced by CP content. Compared with GSS, RSE exhibited a greater neutral detergent fibre digestibility (P<0.01), it did not influence total volatile fatty acids (VFA; P=0.10) but decreased the proportions of acetate and propionate on total VFA (P<0.001) and increased those of butyrate and branched-chain VFA (P<0.001). Microbial efficiency was comparable for GSS and RSE. Results suggest that reduction of dietary CP concentration in DM did not impair in vitro digestibility and microbial growth. The protein mixture containing homemade RSE showed in vitro fermentative properties and microbial growth comparable with those of GSS

Evaluation of the Associative Effects of Rice Straw with Timothy Hay and Corn Grain Using an In Vitro Ruminal Gas Production Technique

“…Nutrient deficiencies in the roughage may be detrimental to the growth of rumen microorganisms (e.g., nitrogen or sulfur) or the ruminant itself (e.g., phosphorus), but positive associative effects were commonly observed when other feed materials contained the needed nutrients. Some studies have suggested that the supplementation of forage with rapidly fermentable carbohydrate sources (i.e., corn grain) would improve microbial growth and feed degradability [43], even in suboptimal nitrogen conditions, because of adaptations in the microbial populations [44,45]. Niderkorn et al [46] studied the associative effects of temperate climate grass and legumes and found an influence on rumen protein degradation between the legume tannins and grass protein.…”