牛粪再生垫料生产过程中物料特性及致病菌变化

不同垫料生产方式因工艺差异导致垫料存在生物安全隐患，不利于垫料技术的推广，滚筒发酵具有高温、快速等优势，探讨其垫料生产过程的致病菌变化特征，可为解决产业问题提供支持。该研究以滚筒好氧发酵生产牛粪再生垫料过程为研究对象，采用平板培养法对夏季和冬季垫料生产过程中滚筒不同位置处奶牛乳房炎主要致病菌（大肠杆菌、链球菌、金黄色葡萄球菌和克雷伯氏菌）数量进行检测，同时检测了物料的理化特性，并进一步探究了影响奶牛乳房炎致病菌变化的主要因素。结果表明，夏、冬季滚筒发酵生产牛粪再生垫料过程中筒仓内温度较稳定，滚筒内部温度可维持在65 ℃以上；成品垫料的含水率均低于45%；链球菌和克雷伯氏菌在垫料成品中均未检出，夏季垫料成品中的大肠杆菌和金黄色葡萄球菌检测数量高于冬季；Pearson相关性分析结果表明，在选取的理化指标中影响致病菌数量变化的最主要因素为滚筒温度，其次为总碳。该研究为滚筒发酵生产牛粪再生垫料的技术应用及推广提供支撑。

[32] Narula R. Pathogen Reduction and factors responsible for pathogen reduction in dairy farm operations treating dairy manure[J]. Biological Engineering, 2011, 4(3): 115-131.

Abstract: The use of recycled manure solids (RMS) as dairy bedding material has become a promising technology with the merits of sustainable manure management and cost saving for purchasing traditional bedding. However, cow dung contains certain amounts of pathogenic bacteria, thus the use of RMS would increase the risk of direct contact of pathogens with cows'' udder. Such serious problem has undermined the use of RMS as dairy bedding material. Drum fermentation for the bedding production has many advantages (i.e. high temperature, short time), thereby it is getting more and more attention. The objective of this study was to investigate the stability and biological safety of RMS production process using drum fermentation in different seasons, and to clarify the factors affecting the growth of pathogenic bacteria in the dairy cows''mastitis. The drum-type RMS producing system employed was composed of a two-stage solid-liquid separator, a horizontal-rotation drum fermentation tank, as well as feeding and discharging components. The automatic control system monitored equipment operation and temperature changes in real time. The drum temperature was obtained by the temperature sensors installed on the inner wall of the drum including inlet, center, and outlet. Samplings were performed from the inlet, 1/3, 2/3, and outlet of the drum. The plate culture method was used to detect the main mastitis pathogenic bacteria (i.e., Eschrichia coli, Staphylococcus aureus, Streptococcus, and Klebsiella) at different positions within the drum during the summer and winter. At the same time, the physical and chemical properties (water content, pH, total carbon, total nitrogen, ash, particle size distribution, roller temperature) of RMS were also tested. Additionally, the main factors affecting the growth of mastitis pathogens was investigated via Pearson correlation analysis.The results indicated that the fermentation temperature during the production process was stable and maintained above 65 oC both in summer and winter, and the final moisture content at the drum outlet was less than 45%. In both seasons, the particle size distribution at different positions of the roller was mainly concentrated at 0.5 mm to 2.0 mm. With the fermentation process, the large particle size gradually converted to small and medium particle size. The number of mastitis pathogens in summer and winter was highest at the drum inlet, and gradually decreased at higher fermentation temperature. At 1/3 of the drum, the number of major mastitis pathogens was significantly reduced. Streptococcus. and Klebsiella. were not detected at the drum outlet in both seasons. However, the number of Eschrichia coli and Staphylococcus aureus at the outlet of the drum in summer was about 3 lgcfu/g higher than that in winter. It may be related to the moisture content of the cow dung at the inlet of the drum. Therefore, the moisture content of the inlet of the drum should be strictly controlled between 50% and 65%. Using the Pearson correlation analysis, it was found that the major factor affecting main mastitis pathogen was drum temperature, followed by total carbon. From the security point of view, RMS should be used immediately after production to avoid environmental impacts. The results found in this study can provide deep insight for the application of drum fermentation technology to produce safer RMS.