紫花苜蓿与甜高粱混合比例对发酵全混合日粮营养品质及有氧稳定性的影响

Effects of Mixing Ratio of Alfalfa and Sweet Sorghum on Nutritional Quality and Aerobic Stability of Total Mixed Ration Silage

本试验旨在探究紫花苜蓿与甜高粱混合比例对发酵全混合日粮(TMR)营养品质及有氧稳定性的影响,进而确定发酵TMR中紫花苜蓿与甜高粱的适宜混合比例。紫花苜蓿与甜高粱按照10∶0(T1组)、7∶3(T2组)、5∶5(T3组)、3∶7(T4组)和0∶10(T5组)混合后,再分别与精料以6∶4混合,制成5种TMR。TMR青贮60 d后开封测定其营养成分含量、发酵品质及有氧暴露0(开封时)、3、6、9、12 d后主要微生物的动态变化。结果显示:1)随着甜高粱比例的增加,发酵TMR中干物质含量逐渐降低,粗蛋白质含量相对增加,其中T2组粗蛋白质含量最高(19.59%),除与T3组差异不显著(P>0.05)外,显著高于其余各组(P<0.05);粗脂肪含量以T5组最低(2.12%);各组中性洗涤纤维含量差异不显著(P>0.05)。2)随着甜高粱比例的增加,发酵TMR中乳酸含量逐渐增加;各组发酵TMR pH均低于4.2,氨氮/全氮均小于10%,均检测到少量的丙酸,未检测到丁酸。3)有氧暴露后,各组发酵TMR中乳酸菌数量随着有氧暴露时间的延长逐渐降低,好氧细菌和酵母菌数量逐渐增加。4)随着甜高粱比例的增加,发酵TMR的能值逐渐降低,T1、T2组发酵TMR提供的能量较其他组高。综合各组TMR青贮后的营养成分含量、发酵品质、有氧稳定性及提供的能量,在贵州地区肉牛育肥生产中推荐发酵TMR中紫花苜蓿与甜高粱的混合比例为7∶3。

The study aims to investigate the effects of mixing ratio of alfalfa and sweet sorghum on nutritional quality and aerobic stability of total mixed ration(TMR)silage,and then to determine the appropriate mixing ratio of those two forages.The mixing ratio of alfalfa and sweet sorghum were 10∶0,7∶3,5∶5,3∶7 and 0∶10,which were recorded as T1,T2,T3,T4 and T5 groups,respectively,and then mixed with concentrate at 6∶4 to formulate 6 TMR.After 60 days of silage,the nutritional component contents,fermentation quality and the dynamic changes of main microorganisms after 0(the moment of opening),3,6,9 and 12 days of aerobic exposure were measured.The results showed as follows:1)the dry matter content in TMR silage gradually de creased with the increasing of the proportion of sweet sorghum,while the crude protein content increased rela tively.The crude protein content in T2 group was the highest(19.59%),which was significantly higher than that in other groups(P<0.05)except T3 group.The ether extract content in T5 group was the lowest(2.12%).There was no significant difference in neutral detergent fiber content among groups(P>0.05).2)With the increasing of the proportion of sweet sorghum,the content of lactic acid increased gradually.The pH of TMR silage in each group was lower than 4.2,the ammonia nitrogen/total nitrogen was less than 10%,and a small amount of propionic acid was detected,while no butyric acid was detected.3)After aerobic exposure,the amount of lactic acid bacteria of TMR silage in each group decreased gradually with the prolongation of aer obic exposure time,while the amounts of aerobic bacteria and yeasts increased gradually.4)The energy values of TMR silage decreased gradually with the increasing of the proportion of sweet sorghum,and the energy pro vided by TMR silage in T1 and T2 groups were higher than other groups.Considering the nutritional compo nent contents,fermentation quality,aerobic stability and energy provided by TMR silage,it is recommended that the mixing ratio of alfalfa and sweet sorghum in TMR silage is 7∶3,which TMR silage can be used in beef production of Guizhou area.