Quantitative analysis of microbial fermentation under normal or high ruminal temperature in continuous cultures

摘要: A dual-flow, continuous-culture system was used to investigate effects of ruminal temperature and forage-to-concentrate ratio in lactation dairy diets on in vitro fermentation characteristics. The experiment was performed in a 2 × 2 factorial design (n = 4). Diets were formulated to maintain different forage-to-concentrate ratios (60:40 or 40:60, DM basis) in the high-forage (HF) or the low-forage (LF) diet, respectively. Four treatments were tested: HF under normal ruminal temperature (NRT; 39°C), LF under NRT, HF under high ruminal temperature (HRT; 41°C), and LF under HRT. Each independent run lasted 11 d (8 d of treatment adaptation and 3 d of data and sample collection). The temperature of the HRT treatment was chosen to mimic ruminal fermentative environment when cows are under heat stress. The HRT increased (P < 0.01) culture pH from 5.73 to 5.82 on average. Total VFA concentration decreased (P …