刈割期和添加剂对苜蓿青贮发酵品质和 CNCPS蛋白组分的影响

Effect of mowing period and additives on fermentation quality and CNCPS protein components of alfalfa silage

为研究刈割时期及添加剂对苜蓿(Medicago sativa)青贮品质的影响,本试验选择2个茬次,现蕾、初花、盛花3个时期刈割,并以无添加(CK)、丙酸钠(SP,0.5%)、乳酸菌(LD,106 cfu·g^(-1))3种处理进行苜蓿青贮制作,在贮存45d后取样,分析其发酵品质及营养价值。结果发现,随着收获时期的延迟,青贮苜蓿pH值呈下降的趋势;丙酸钠及乳酸菌添加剂的添加对苜蓿青贮饲料的发酵品质有显著的改善作用;随着同一茬次生育期的延长,青贮苜蓿中的粗蛋白(CP)含量显著降低(P<0.05);刈割时期可显著降低苜蓿青贮饲料的pH值并明显提高乳酸含量(P<0.05),对乙酸及丙酸含量影响不显著(P>0.05)。而添加剂可显著增加乙酸含量(P<0.05),两者存在显著互作效应(P<0.05)。添加乳酸菌的现蕾期苜蓿青贮品质最佳。应用康奈尔净碳水化合物-蛋白质体系(CNCPS)提出的方法测定表明,第1茬盛花期的苜蓿青贮饲料的非蛋白氮(PA)含量较高,苜蓿青贮饲料各处理中的中速降解蛋白质(PB2)含量均是占可降解蛋白质(PB)含量的最大比例。

The study was designed to evaluate the effects of mowing period and additives on the fermentation quality ofalfalfa. Alfalfa was mowed at two harvesting time points, in three periods（budding, early flowering, and full flowering）, with no additives （CK）, and withthe addition of sodium propionate （0.5%） and lactic acid bacteria （106 cfu · g-1）. After 45 days of storage, fermentation quality and nutritive value were analyzed, pH decreased with delay in harvest. The addition of sodium propionate and lactic acid bacteria had significant effects on the fermentation quality of alfalfa silage. CP content of alfalfa silage was significantly decreased with the growth period extension of the same cropping period. The pH of alfalfa silage decreased significantly,and lactic acid content increased （P〈0.05） significantly; the effects of acetic acid and propionic acid were not significant （P〈0.05）, and the interaction effect was significant （P〈0.05）. The quality of the budding stage alfalfa silage inoculated with lactic acid bacteria was the best. The content of non-protein nitrogen （PA） in the first crop at full-bloom stage was higher, and PB2 content in alfalfa silage was the highest relative to PB content.