Influence of yucca extract on ruminal metabolism in cows3

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Abstract
Two trials were conducted to determine the influence of yucca extract on ruminai digestion, fermentation, and ammonia patterns using ruminally and duodenally cannulated dairy cows. In Trial 1, urea at 0 or 1% of the diet and yucca extract at 0 or 4 g/d formed four dietary treatments in a 2 × 2 factorial arrangement. The experimental design was a 4×4 Latin square with 15-d periods. Duodenal digesta were sampled every 6 h during the last 4 d of each period to determine OM and ADF digestibilities and bacterial protein synthesis in the rumen using Cr2O3 and 15N markers. Ruminai digestibilities were (percentage): OM 46.3 vs 43.0%, and ADF 35.9 vs 41.4%, with or without Deodorase®. Microbial protein entering the duodenum averaged 2.7 vs 3.1 kg/d for the respective treatments. Ruminai measurements were not affected by treatment (P >.10). In Trial 2, five cows were used in a 5 × 5 Latin square with 7-d periods. Treatments were 0, 2, 4, 6, and 8 g/d of yucca extract administered via ruminai cannulas. Ruminai fluid was sampled 0, 1, 2, 4, 7, 11, 16, and 22 h after feeding during the last 2 d of each period. Average ruminai NH3 N ranged from 31.4 to 35.4 mg/ dL, pH 5.99 to 6.18, and total VFA from 120 to 129 mM, and all did not differ among treatments (P >.10). Yucca extract administered at 4 g/d did not significantly affect ruminai digestibilities of OM and ADF, and up to 8 g/d did not affect ruminai NH3, pH, or VFA.

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