Effects of increasing level of dietary rice straw on chewing activity, ruminal fermentation and fibrolytic enzyme activity in growing goats

Abstract

Effects of increasing dietary rice straw on chewing activity, ruminal fermentation,and fibrolytic enzyme activity in growing goats were investigated in a 4x4 Latin Square experiment. The goats were offered four diets with an increasing proportion of rice straw (i.e. 0.05, 0.10, 0.15 and 0.20, respectively, on dry matter basis). Increasing levelof rice straw increased (Plinear effect<0.05) the time spent on eating, ruminating, and chewing. The ruminal pH and acetate: propionate ratio were increased (P linear effect<0-05), while the NH3-N concentration was decreased (Plinear effect<0.01). Increasing level of rice straw in the diet increased (Plinear effect≤ molar proportion of acetate and isovalerate, and decreased (Plinear effect<0.01) molar proportion of propionate. The CMCase, xylanase and cellobiase activities in the rumen were decreased (Pun^ eff^O.05) with increasinglevel of dietary rice straw, whereas the avicelase activity was increased (Plineareffect<0.01) . In summary, increased level of rice straw elevated the dietaryneutral detergent fibre (NDF) content in the diet and had a great impact on chewing activityand ruminal fermentation.