The objective was to evaluate effects of rumen-protected methionine （RP-Met） supplementation on rumen fermentation, lactation performance and plasma characteristics in dairy cows. Twenty-four multiparous （2.2 - 0.4...The objective was to evaluate effects of rumen-protected methionine （RP-Met） supplementation on rumen fermentation, lactation performance and plasma characteristics in dairy cows. Twenty-four multiparous （2.2 - 0.40 parity） Holstein dairy cows, averaged 620 ± 12.3 kg of BW, 68 ± 2.5 day in milk and daily milk production averaged 26.0 ±0.3 kg/cow were used in a replicated 4 × 4 Latin square experiment. The treatments were： control （without RP-Met）, LRP-Met, MRP-Met and HRP-Met with 20, 40 and 60 g RP-Met per cow per day, respectively. RP-Met was hand-mixed into the top one-third of the daily ration. Experimental periods were 30 days with 15 d of adaptation and 15 d of sampling. Dry matter （DM） intake and milk yields were not affected （P 〉 0.05） with increasing RP-Met supplementation. Yields of 4%FCM, ECM, milk fat and milk protein were higher （P 〈 0.03） for RP-Met supplementation than control and were quadratically （P 〈 0.05） changed due to the higher percentage of milk fat and protein for RP-Met supplementation than control （P 〈 0.03）. Ruminal pH tended to be lower （P = 0.071） for RP-Met supplementation than control, whereas total VFA concentration tended to be higher （P = 0.086） for RP-Met supplementation than control. Ratio of acetate to propionate decreased linearly （P = 0.001） from 4.01 to 3.57 as RP-Met supplementation increased due to the increase in propionate production. Digestibilities of DM, OM, CP, NDF and ADF in the total tract were higher （P 〈 0.05） for RP-Met supplementation than control and were quadratically （P 〈 0.05） increased with increasing RP-Met supplementation. Plasma concentrations of glucose not affected （P 〉 0.05） with RP-Met supplementation, Plasma concentrations of non-esterified fatty acids （NEFA） were significantly lower （P = 0.017） for RP-Met supplementation than control and were linearly （P = 0.011） changed. Plasma concentrations of beta-hydroxybutyrate tended to be lower （P = 0.068） for RP-Met supplementation than control and were linearly （P = 0.001） changed. The present results indicate that supplementation of diet with RP-Met improved the content of milk fat and protein, rumen fermentation and feed digestion, decreased plasma concentrations of NEFA. It was suggested that the RP-Met stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum RP-Met dose was about 25 g RP-Met per cow per day.展开更多
文摘The objective was to evaluate effects of rumen-protected methionine （RP-Met） supplementation on rumen fermentation, lactation performance and plasma characteristics in dairy cows. Twenty-four multiparous （2.2 - 0.40 parity） Holstein dairy cows, averaged 620 ± 12.3 kg of BW, 68 ± 2.5 day in milk and daily milk production averaged 26.0 ±0.3 kg/cow were used in a replicated 4 × 4 Latin square experiment. The treatments were： control （without RP-Met）, LRP-Met, MRP-Met and HRP-Met with 20, 40 and 60 g RP-Met per cow per day, respectively. RP-Met was hand-mixed into the top one-third of the daily ration. Experimental periods were 30 days with 15 d of adaptation and 15 d of sampling. Dry matter （DM） intake and milk yields were not affected （P 〉 0.05） with increasing RP-Met supplementation. Yields of 4%FCM, ECM, milk fat and milk protein were higher （P 〈 0.03） for RP-Met supplementation than control and were quadratically （P 〈 0.05） changed due to the higher percentage of milk fat and protein for RP-Met supplementation than control （P 〈 0.03）. Ruminal pH tended to be lower （P = 0.071） for RP-Met supplementation than control, whereas total VFA concentration tended to be higher （P = 0.086） for RP-Met supplementation than control. Ratio of acetate to propionate decreased linearly （P = 0.001） from 4.01 to 3.57 as RP-Met supplementation increased due to the increase in propionate production. Digestibilities of DM, OM, CP, NDF and ADF in the total tract were higher （P 〈 0.05） for RP-Met supplementation than control and were quadratically （P 〈 0.05） increased with increasing RP-Met supplementation. Plasma concentrations of glucose not affected （P 〉 0.05） with RP-Met supplementation, Plasma concentrations of non-esterified fatty acids （NEFA） were significantly lower （P = 0.017） for RP-Met supplementation than control and were linearly （P = 0.011） changed. Plasma concentrations of beta-hydroxybutyrate tended to be lower （P = 0.068） for RP-Met supplementation than control and were linearly （P = 0.001） changed. The present results indicate that supplementation of diet with RP-Met improved the content of milk fat and protein, rumen fermentation and feed digestion, decreased plasma concentrations of NEFA. It was suggested that the RP-Met stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum RP-Met dose was about 25 g RP-Met per cow per day.
