不同品种和刈割时间对苜蓿青贮发酵品质及蛋白质降解的影响

Effect of Different Varieties and Cutting Time on Fermentation Quality and Protein Degradation of Alfalfa Silage

为探究不同品种以及同日内不同刈割时间对苜蓿青贮发酵品质及蛋白质降解的影响,采用4个苜蓿品种,分别于同日6∶00、12∶00、18∶00刈割,室温发酵56d后开封,分析发酵品质、微生物组成和蛋白组分。结果表明,不同品种苜蓿的粗蛋白、中性洗涤纤维、酸性洗涤纤维和可溶性糖(WSC)含量以及附着微生物的数量存在显著性差异(P<0.05);推迟刈割时间,苜蓿原料的干物质,WSC含量以及附着微生物数量显著增加(P<0.05)。品种A与C的发酵品质显著优于品种B与D(P<0.05),其乳酸含量较高而pH值、乙酸与氨态氮含量较低(P<0.05)。随着刈割时间的推迟,所有苜蓿青贮的乳酸含量及乳乙比显著增加(P<0.05),pH值、乙酸、丁酸、非蛋白氮与氨态氮含量显著降低(P<0.05),显著抑制蛋白降解。综上所述,不同品种的原料特性显著影响苜蓿青贮发酵品质,推迟刈割时间可以有效改善青贮发酵品质,减少蛋白质的降解。

To investigate the effect of different varieties and cutting time on fermentation quality and protein degradation of alfalfa silage,four varieties were mowed at 6[KG-*4]∶[KG-*4]00,12[KG-*4]∶[KG-*4]00,18[KG-*4]∶[KG-*4]00 on the same day and fermented at the room temperature.After 56 days of ensiling,fermentation quality,microbial and protein composition were analyzed.The results showed that there were significant differences in contents of crude protein,neutral detergent fiber,acid detergent fiber,water soluble carbohydrate(WSC)and microbial counts among different varieties(P<0.05).Contents of dry matter,WSC and epidemic microorganisms of alfalfa materials were significantly increased with postponing the cutting time(P<0.05).The fermentation quality of variety A and C was significantly superior than that of variety B and D(P<0.05),which were characterized by higher lactic acid content and lower pH value,acetic acid and ammonia nitrogen contents(P<0.05).With postponing the cutting time,lactic acid content and lactic to acetic acid ratio were significantly increased(P<0.05),while pH value,contents of acetic acid,butyric acid,nonprotein nitrogen and ammonia nitrogen were dramatically decreased(P<0.05),which indicated that protein degradation was inhibited effectively.In conclusion,characteristics of alfalfa materials significantly affected fermentation qualities.Meanwhile,postponing the cutting time can improve fermentation qualities and inhibit the protein degradation effectively.