苜蓿干草和秸秆组合体外发酵营养特性及其利用研究

Study on in vitro fermentation characteristics of alfalfa hay mixed with straw and their combined utilization

应用体外发酵产气技术,评价了苜蓿Medicago sativa干草和玉米Zea mays、小麦Triticum aestivum秸秆分别以0∶100、25∶75、50∶50、75∶25和100∶0进行两两组合时的发酵特性。结果表明:不同比例组合产气量(GP)、理论最大产气量(A)、产气速率(b)及产气延滞时间(LAG)变化趋势不同;苜蓿干草与玉米秸秆按50∶50的比例或苜蓿干草与小麦秸秆按75∶25的比例组合时的效应明显好于其他组合。48 h产气量与粗蛋白(CP)(P<0.05)及中性洗涤可溶物(NDS)含量呈正相关关系,而与中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、半纤维(HC)含量及NDS/CP(P<0.01)呈负相关关系;理论最大产气量与CP、NDS的含量呈正相关关系,与NDF、ADF、HC和NDS/CP(P<0.01)呈负相关关系;产气速率与CP(P<0.01)、HC(P<0.01)、NDS(P<0.01)呈极显著正相关关系,分别与NDF(P<0.01)、ADF(P<0.01)、NDS/CP(P<0.05)呈负相关关系;产气延滞时间与饲草料的主要营养成分的相关关系不明显,只与NDS/CP(P<0.05)呈显著正相关关系。结论认为,饲草中非结构性碳水化合物与蛋白质比例决定了体外发酵产气的特性。生产实践中应针对低质粗饲料营养特性,适当添补易发酵或高蛋白牧草,提高粗饲料利用效率。

An experiment was conducted to investigate in vitro gas production characteristics of mixed forages. The mixed forages investigated in this experiment were alfalfa hay mixed with corns straw, alfalfa hay mixed with wheat straw, and corns straw mixed with wheat straw, all mixtures replicated at proportions of 0 ： 100, 25 ： 75, 50 ： 50, 75 ： 25, and 100 ： 0. The results show that the maximum theoretic gas production, rate of gas production and lag time of gas production present different changing patterns, respectively, with the variation of mixed proportion. The obvious positive associative effects are noted when the mixture of alfalfa hay was mixed with corn stalk with the proportion of 50 ： 50 or alfalfa hay was mixed with wheat straw with the proportion of 75 ： 25. Correlation analyses indicated that cumulative gas production at 48 h was positively related to the content of CP（P〈0.05） and NDS, and negatively related to the content of NDF, ADF, HC and the ratio of NDS to CP. The theoretical maximum gas production CP and NDS, and negatively related to the content of NDF, ADF, HC and the ratio of NDS to CP （P〈0.01）. The rate of gas production was the content of CP （P〈0.01）, HC（P〈0.01）, NDS（P〈0.01）, and negatively related to the content of NDF（P〈0.01）, ADF（P〈0.01） and the ratio of NDS to CP （P〈0.05）. The lag times were positively related to the ratio of NDS to CP （P〈0.05）, but had little correlation with the other major nutritional components of forage grass and feed. It is therefore suggested that the in vitro gas production characteristics depend upon the balance of non-structural carbohydrate and crude protein, rich in fermentable carbohydrate and/or digestible protein into low quality forage and adding pastures is essential and necessary to improve utilization efficiency of crude forage.