Effects of different proportions of dietary structural and nonstructural carbohydrates on ruminal fermentation and microbial growth efficiency in sheep

摘要

Four sheep were used in a 4×4 Latin square design to study the effect of different dietary proportions of structural carbohydrate (SC) and nonstructural carbohydrate (NSC) (SC:NSC ratio: 0.55, 1.12, 2.25 and 5.24) on rumen fermentation and microbial growth efficiency. As the dietary SC: NSC ratio increased, ruminal pH and ammonia concentration increased (P＜0.001), but total rumen VFA concentration decreased (P＜0.001). When dietary SC:NSC ratio increased from 0.55 to 1.12, the molar percentage of acetate increased (P＜0.001) and the molar proportion of propionate decreased (P＜0.001). However, when the ratio increased from 1.12 to 5.24, there were no changed molar percentages of acetate and of propionate. Both daily microbial nitrogen production and microbial efficiency decreased with increasing dietary SC:NSC ratio.