长江下游地区中国荷斯坦奶牛生乳中菌落总数的影响因素分析

Factors affecting aerobic plate count in the milk of Chinese Holstein cows in the lower reaches of the Yangtze River

摘要:

【背景】随着人们生活水平和健康意识的提高，作为部分乳制品的原料，生乳的质量安全问题显得尤为重要。【目的】检测长江下游地区某集约化牧场中国荷斯坦奶牛生乳中菌落总数、总大肠菌群数的真实水平，同时对影响其变化的生理因素和环境因素进行探讨。【方法】以中国荷斯坦奶牛生乳为研究对象，用乳房炎快速诊断剂检测乳房炎感染情况，菌落总数、总大肠菌群数和环境细菌数的检测方法参照国家标准。对采集的生乳样本进行细菌常规分离鉴定，同时收集乳成分变化数据。【结果】多因素方差分析结果表明，不同泌乳阶段和不同产奶量对荷斯坦奶牛生乳中菌落总数的影响显著(P<0.05)和极显著(P<0.01)；体况、泌乳阶段、胎次、产奶量及乳区对大肠菌群数均无显著影响(P>0.05)。夏季生乳的菌落总数、大肠菌群数均极显著地高于其他季节(P<0.01)；场区内各牛舍的不同卫生环境及细菌数对菌落总数、大肠菌群数的影响均在显著以上(P<0.05)。不同乳房炎的感染程度对菌落总数影响极显著(P<0.01)。细菌鉴定结果是葡萄球菌属和杆菌属感染居多，链球菌属感染几乎没有。菌落总数的变化对乳蛋白率影响不显著(P>0.05)，对乳脂率的影响极显著(P<0.01)。【结论】随机采样泌乳牛群的不同生理和病理状况、外界不同饲养条件及卫生环境对生乳中菌落总数和大肠菌群数有不同程度的影响，生乳的乳脂率与细菌总数变化负相关。

Abstract:

[Background] With the increase of living standards and health awareness, quality and safety of milk are acquiring great concern. [Objective] To investigate aerobic plate count (APC) and total number of Coliform Group (TCG) in the milk of lactating Chinese Holstein cows from an intensive farm located in the lower reaches of the Yangtze River, China, by using different bacteriological methods. The causative factors of APC and TCG were also explored. [Methods] Taking the milk of Chinese Holstein cows as the research object, mastitis detection using mastitis rapid diagnostic agents, APC, TCG and the number of bacteria in the environment detection method with reference to national standards. The collected raw milk samples were subjected to routine isolation and identification of the bacteria, and the milk composition change data was collected. [Results] The results of multivariate analysis of variance showed that different lactation stages and different milk yields had significant (P<0.05) and significant (P<0.01) effects on the total number of colonies in Holstein cows? raw milk. Body condition score, milk yield, stage of lactation, parity and udder quarters had no significant effect (P>0.05) on TCG; APC and TCG measured in summer were significantly (P<0.01) higher than other seasons. Effect of the number of bacteria in different environment on APC and TCG were significant (P<0.05) above. With the increase of mastitis degree, APC and TCG in milk increased, with a significant difference in aerobic plate count for different degree of mastitis (P<0.01). Bacterial identification results in the majority of Staphylococcus and Bacillus infections and almost no Streptococcus infection. The change of the total number of colonies had no significant effect on the rate of milk protein (P>0.05), but had a significant effect on milk fat percentage (P<0.01). [Conclusion] Different physiological and pathological conditions of the randomly sampled lactating cows and the external feeding conditions and hygiene environment had different effects on APC and TCG in the raw milk. The milk fat percentage of raw milk was negatively correlated with the change in total number of bacteria.