Abstract: The objective of this study was to evaluate the effects of replacing alfalfa(Medicago sativa L.) with different proportions of king grass ‘Reyan No.4’(Pennisetum purpureum×P.americana ‘Reyan No.4’) on the fermentation quality,nutritional composition and aerobic stability of the total mixed ration(TMR) silage. The replacement ratios of king grass ‘Reyan No.4’ were set as 0% (H₀,alfalfa control group),18%(H₁₈),30%(H₃₀) and 42%(H₄₂),respectively. The silages were opened at 60 days ensiling and the fermentation quality and nutrient composition were analyzed,the aerobic stability was evaluated after 0,3,6,9,12 days of aerobic exposure. The results showed that with the increase of the replace ratio of king grass Reyan No.4,the lactic acid contents,the pH value and the ammonia nitrogen/total nitrogen in FTMR gradually decreased. The ammonia nitrogen/total nitrogen of all treatments were less than 100 g·kg^-1TN while butyric acid were not detected. After 60 days fermentation,water soluble carbohydrates contents of H₄₂ treatments were significantly higher than that of H₀and H₁₈(P<0.05). Compared with raw material,dray matter and crud protein decreased in all treatments. The decrease of dry matter content and crude protein content was the least in H₄₂. During aerobic exposure,the amount of aerobic bacteria,yeast and molds gradually increased with the extension of aerobic exposure time,and the amount of lactic acid bacteria gradually decreased with the extension time. The pH value did not exceed 4.2 in the H₄₂ group,which indicated the best aerobic stability. According to the economic benefit analysis,the feed cost of H₄₂ is the lowest. It was most appropriate to select the H₄₂ group as the suitable choice for TMR fermentation.

Key words: King grass ‘Reyan No.4’, Alfalfa, Fermented total mixed ration, Fermentation quality, Aerobic stability

摘要： 本试验旨在探讨不同比例‘热研4号’王草（Pennisetum purpureum×P.americana ‘Reyan No.4’）替代紫花苜蓿（Medicago sativa L.）对全混合日粮发酵品质及有氧稳定性的影响。试验设‘热研4号’王草替代比例为0%（H₀，紫花苜蓿对照组），18%（H₁₈），30%（H₃₀），42%（H₄₂）4个处理，青贮60 d后开袋取样，分析其发酵品质和营养成分，并分别在有氧暴露的第0，3，6，9，12 d取样评定其有氧稳定性。结果表明：随着热研4号王草替代比例的增加，发酵全混合日粮中乳酸含量、pH及氨态氮/总氮逐渐减小，各组氨态氮/总氮小于100 g·kg^-1TN且均未检测到丁酸；发酵60d后，H₄₂组水溶性碳水化合物含量显著高于H₀，H₁₈组（P<0.05），与发酵前相比，各组干物质和粗蛋白含量有所下降，H₄₂组干物质和粗蛋白含量下降最小；有氧暴露期间，好氧细菌、酵母菌和霉菌的数量逐渐增加，乳酸菌的数量逐渐降低，H₄₂组pH在12 d内未超过4.2，有氧稳定性最好。由经济效益分析可知，H₄₂组饲料成本最低。综上所述，选用H₄₂组进行全混合日粮发酵最为适宜。

关键词: 热研4号王草, 紫花苜蓿, 发酵全混合日粮, 发酵品质, 有氧稳定性