甜高粱与苜蓿混合青贮过程pH和主要微生物变化规律的研究

Study on the Change of pH and Main Microorganisms during the Process of Mixed Silages Made of Sweet Sorghum and Alfalfa

本研究旨在探讨甜高粱与苜蓿混合青贮发酵过程中pH和主要微生物数量的变化趋势。本研究以甜高粱和苜蓿按照5种不同比例(甜高粱占比为0%、25%、50%、75%、100%)进行混合制作青贮,在混合青贮后的不同时间进行取样,测定混合青贮样品的pH及乳酸菌、酵母菌、霉菌、大肠杆菌、好氧菌主要微生物的含量。结果表明,随着青贮时间的延长,5种比例混合青贮pH在青贮初期下降较快,到45 d下降到了4. 2左右,后期趋于正常水平。25%的青贮饲料中乳酸菌数量在第11 d达到最高峰,为109数量级,而后缓慢下降,最后逐渐稳定。酵母菌的数量整体呈逐渐下降趋势,在青贮第11 d出现短暂高峰,最后逐渐稳定。霉菌数量在一定的时间内短暂上升,之后逐渐减少,75%和100%的青贮饲料在第30 d检测不到霉菌的存在。大肠杆菌数量在青贮初期数量较多,之后迅速下降直至检测不出。好氧菌在青贮的初期呈上升趋势,之后则迅速下降。综上所述,甜高粱与苜蓿混合青贮发酵过程中几种主要微生物均发生了明显变化,对甜高粱与苜蓿混合青贮有一定的指导意义。

The aim of this study was to investigate the changing trend of pH and main microbial quantity during the fermentation of mixed silages made of sweet sorghum and alfalfa.In the experiment,silage was mixed with sweet sorghum and alfalfa in five different proportions(sweet sorghum0%,25%,50%,75%,100%),and sampled at different times after the mixed silage.The pH of the mixed silage sample and the contents of lactic acid bacteria,yeasts,fungi,coliform and aerobic bacteria were determined.The results showed that with the prolongation of silage time,the pH of five kinds of hybrid silage decreased rapidly in the early stage of silage,and to 45 d basically decreased to 4.2,reaching the normal level in the later stage.The amount of lactic acid bacteria in 25% proportion silage reached the peak at 11th day,which was 109 orders of magnitude,then slowly decreased,and finally became stable.The number of yeasts declined gradually,peaked briefly on the11th day of silage,and finally stabilized.The number of molds briefly increased for a certain period of time,then gradually decreased until the 30th day it could not be detected in the 75% and 100%silage.The number of Escherichia coli was higher in the initial stage of silage,and then decreased rapidly until it could not be detected.Aerobic bacteria showed an upward trend in the early stage of silage and then declined rapidly.In summary,several main microorganisms in the fermentation process of sweet sorghum and alfalfa mixed Silage have significantly changed,which has a certain guiding significance for the mixed Silage of sweet sorghum and alfalfa.