不同中性洗涤纤维与淀粉比例饲粮对体外瘤胃发酵的影响

Effects of Different Neutral Detergent Fiber to Starch Raito Diets on Rumen Fermentation in Vitro

本试验旨在探讨不同中性洗涤纤维与淀粉比例（NDF/starch）饲粮对体外瘤胃发酵的影响。选用玉米青贮、燕麦干草和玉米调整饲粮NDF/starch,配制0.86（Ⅰ）、1.13（Ⅱ）、1.56（Ⅲ）和2.38（Ⅳ）4种NDF/starch的全混合日粮,采用3头体况良好且装有永久性瘤胃瘘管的荷斯坦奶牛作为瘤胃液的供体动物,利用体外发酵试验结合动态产气实时记录技术,测定累积产气量（2、6、12、24、36、48 h）、产气动力学参数和瘤胃发酵特性指标。结果表明：1）随着饲粮NDF/starch的提高,发酵48 h体外干物质降解率逐渐下降,I、Ⅱ组均显著高于Ⅲ、Ⅳ组（P〈0.05）;48h累积产气量和理论最大产气量呈下降趋势,Ⅳ组显著低于其他各组（P〈0.05）;组间达1/2理论最大产气量的时间、最大产气速率无显著差异（P〉0.05）。2）NDF/starch对发酵液氨态氮和微生物蛋白浓度影响不显著（P〉0.05）。3）随着饲粮NDF/starch的增加,p H、乙酸/丙酸、乙酸/总挥发性脂肪酸呈显著或极显著增加（P〈0.05或P〈0.01）,总挥发性脂肪酸、丙酸、丁酸浓度及丙酸/总挥发性脂肪酸呈显著或极显著下降（P〈0.05或P〈0.01）。4）不同NDF/starch饲粮营养水平与体外发酵参数相关性分析表明,48 h累积产气量、理论最大产气量与淀粉含量、中性洗涤可溶物（NDS）含量、中性洗涤可溶物/粗蛋白质（NDS/CP）、非纤维性碳水化合物（NFC）含量呈极显著正相关关系（P〈0.01）,而与中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）含量呈极显著负相关关系（P〈0.01）。综合而言,本试验条件下,体外产气法测定饲粮NDF/starch在0.86~1.13之间对体外瘤胃发酵较好。

This experiment was conducted to examine the effects of different neutral detergent fiber to starch ratio（NDF/starch） diets on rumen fermentation in vitro.Corn silage,dried oat hay and corn were used to adjust the NDF/starch of total mixed rations,and NDF/starch was 0.86（Ⅰ）,1.13（Ⅱ）,1.56（Ⅲ） and 2.38（Ⅳ）,respectively.Three healthy Holstein cows fitted with permanent ruminal cannulas were used as the donor of rumen fluid.Accumulative gas production in 2,6,12,24,36 and 72 h,gas production kinetic parameters and rumen fermentation parameters of the diets were determined by combining the method of in vitro rumen fermentation and the technique of real-time recording of gas production.The results showed as follows： 1） with the increase of dietary NDF/starch,in vitro dry matter degradation rate after 48 h fermentation was decreased,and groups Ⅰ and Ⅱ were significantly higher than groups Ⅲ and Ⅳ（P〈0.05）; accumulative gas production in 48 h and theoretical maximum gas production ranked in descending order,and group Ⅳ was significantly higher than the other groups（P〈0.05）.No significant differences in the time of reaching 1/2 theoretical maximum gas production and the maximum gas production rate among all groups were observed（P〈0.05）.2） The concentrations of ammonia nitrogen（NH3-N） and microbial protein in fermentation fluid were not affected by dietary NDF/starch（P〈0.05）.3） With the increase of dietary NDF/starch,p H,acetate/propionate and acetate/total volatile fatty acid（TVFA） were significantly increased（P〈0.05 or P〈0.01）,but TVFA,propionate,butyrate and propionate/TVFA were significantly decreased（P〈0.05 or P〈0.01）.4） Correlation between nutrient levels of different NDF/starch diets and fermentation parameters in vitro showed that the accumulative gas production in 48 h and theoretical maximum gas production were significantly positive related to the contents of starch,neutral detergent soluble（NDS） and non-fiber carbohydrate（NFC）,as well as NDS/CP（P〈0.01）,and also were significantly negative related to neutral detergent fiber（NDF） and acid detergent fiber（ADF）contents（P〈0.01）.In conclusion,the results of in vitro gas production method indicate that dietary NDF/starch between 0.86 and 1.13 can promote rumen fermentation under the present experimental conditions.