Microbiological Quality Of Raw Cow's Milk And Its Association Factors In China

Milk is highly nutritious,however,because of its nutritional properties,milk is also a good growth matrix for a variety of spoilage and potentially pathogenic microorganisms.Micoorganism in raw milk is a risk for human health.With the rapid development of our country's economy,the increasing demand for dairy products,milk safety problems become the focus of social attention.Therefore,it is important to research microb and pathogens and its risk factor in raw milk in China,in order to control the microbial contamination levels and milk safety risk in raw milk.Total bacteria count(TBC)and presence of pathogens in raw milk in China(Beijing,Inner Mongolia,Shandong and Guangdong)with the associated risk factor were be evaluated.A total of 560 raw milk samples were collected from 140 dairy herds in all seasons.TBC,S.aureus,E.coli,B.cereus,Salmonella,L.monocytogenes,and Campylobacter.were be detected.1.140 dairy herds were selected in different areas including small size(1-199), small-medium size(200-499),medium size(500-999)and lager size(>1000),and 560 raw milk were sampled in these herds in all seasons.TBC in raw milk and its risk factor were analyzed.The results showed that 91.25%raw milk samples with TBC<2×10~6 CFU/mL and 40%<1×10~5CFU/mL.Herd size,season and mastitis effect on TBC in raw milk(P<0.05).TBC in small-medium herds were higher than others herds significantly.TBC in summer were higher than other seasons significantly.TBC in herd with mastitis were higher than other herds significantly.2.The prevalence of S.aureus,E.coli and their risk factors in raw milk were evaluated.The prevalence of S.aureus and E.coli was 50.36%and 44.27%.The prevalence of S.aureus and E.coli in raw milk in small herds and small-medium herds were higher than others significantly(P<0.05).The prevalence of S.aureus and E.coli in raw milk in summer were higher than that in winter significantly(P<0.05).Milking frequency and disinfection frequency influenced the prevalence of S.aureus in raw milk(P<0.05).The higher frequence of milking and disinfection,the lower prevalence of E.coli in raw milk(P<0.05).The correlation between TBC and prevalence of S.aureus and E.coli is a significant(P<0.05).3.In total,160 raw milk samples collected from 2014 to 2015 and examined by culture methods to isolate B.cereus.Fifty-five samples(34.38%)were positive.The prevalence of B.cereus in raw milk was significantly(p<0.01)lower in winter(15%)than in summer(50%).The highest prevalence of B.cereus in raw milk was seen in samples collected from small-to-medium sized dairy herds in summer.There is no association between prevalence of B.cereus in raw milk and herd size,DHI and frequency of milking and disinfection.4.In total 560 raw milk samples,the prevalence of L.monocytogenes, Salmonella and Campylobacter was 1.96%,2.32%and 1.61%.The highest prevalence of L.monocytogenes was in Inner Mongolia.The prevalence of Salmonella in Beijing,Inner Mongolia and Shandong was higher than Guangdong.The highest prevalence of Campylobacter was in Inner Guangdong.The prevalence of Campylobacter in raw milk in summeri was higher than other seasons.5.Raw milk samples in China were analyzed based on high-throughput sequencing of the V3-V4 region of the 16S rDNA.The results of microbial diversity analysis showed that the Shanmon index and Simpson index in low TBC of raw milk were higher than that in high TBC of raw milk.At the genus level,Acinetobacter is dominant in low TBC of raw milk;Stenotrophomonas is the major bacterial in high TBC of raw milk.Contamination of raw milk with bacterial pathogens is low in China,most(91.25%)of raw milk samples met the TBC of the China national standard(<2×106 CFU/mL),suggesting that our conntry raw milk standards conform to current situation of the development of dairy industry in our country.However,the prevalence of pathogens detected in our study in raw milk cannot be avoided in China,there was low risk of pathogens in raw milk in China.The prevalence of S.aureus,E.coli and B.cereus in raw milk was much higher than that of Campylobacter,Salmonella and L.monocytogene.There were higher contamination of microbio in raw milk in Inner Mongolia and Shandong.The highest prevalence of pathogens in raw milk in small-medium herds in summer.Area,season,herd size,mastitis,bulk tank temperature,DHI implementation,milking frequency and disinfection frequency were also associated with microbiological quality in raw milk.Thus,it is essential for dairy farmers and producers to strengthen hygienic practices in summer.Suggestions to promote large-scale farming,strengthen the management practice and hygiene level,increase frequency of milking and the disinfection.Shanmon index and Simpson index in low TBC of raw milk were higher than that in high TBC of raw milk.At the genus level,Acinetobacter is dominant in low TBC of raw milk;Stenotrophomonas is the major bacterial in high TBC of raw milk.Our results could be of great value for the government to develop a risk assessment for this sort of product and better control food safety and hazards.