Effects of wheat dried distillers' grains with solubles and cinnamaldehyde on in vitro fermentation and protein degradation using the Rusitec technique

This study was conducted to evaluate the effect of wheat dried distillers' grains with solubles (DDGS) and cinnamaldehyde (CIN) on in vitro fermentation and microbial profiles using the rumen simulation technique. The control substrate (10% barley silage, 85% barley grain and 5% supplement, on dry matter basis) and the wheat DDGS substrate (30% wheat DDGS replaced an equal portion of barley grain) were combined with 0 and 300 mg CIN/l of culture fluid. The inclusion of DDGS increased (p0.05) the concentration of volatile fatty acids (VFA) and the molar proportion of acetate and propionate. Dry matter disappearance (p = 0.03) and production of bacterial protein (p0.01) were greater, whereas the disappearances of crude protein (CP) and neutral detergent fibre were less (p0.01) for the DDGS than for the control substrate. With addition of CIN, concentration of total VFA decreased and fermentation pattern changed to greater acetate and less propionate proportions (p0.01). The CIN reduced (p0.01) methane production and CP degradability. The copy numbers of Fibrobacter, Prevotella and Archaea were not affected by DDGS but were reduced (p0.05) by CIN. The results indicate that replacing barley grain by DDGS increased nutrient fermentability and potentially increase protein flows to the intestine. Supplementation of high-grain substrates with CIN reduced methane production and potentially increased the true protein reaching the small intestine; however, overall reduction of feed fermentation may lower the feeding value of a high-grain diet.