Factors Affecting Aerobic Plate Count And Relationship Between Aerobic Plate Count And Endotoxin In The Milk Of Chinese Holstein At Intensive Farms In South China

With the increase of living standards and health awareness, the quality and safety issues of raw milk arise great concern. The bacteria in raw milk propagate fast when the condition is suitable, which could greatly reduce the nutritional value of milk and increase the risk of food safety. Even Pasteurized milk may still contain toxins. These issues become worries when people consume milk and milk products. In2010, the new national standard on raw milk has aroused hot discussion about RM standard, especially focusing on new requirements of raw milk APC. This study investigated aerobic plate count and total number of Coliform group in the milk of lactating Chinese Holstein from intensive farms in South China using different bacteriological methods. The causative factors of aerobic plate count and total number of Coliform group were also explored. Additionally, its relationship with endotoxin and content of endotoxin in the cow milk was explored through immunological LAL gel method. The study included the following experiments:1. Tracking milk samples collected from2012to2013in the Yangzhou region from433lactating dairy cows concentrately and in accordance with the national standard method, we measured Aerobic plate count and Total number of Coliform Group and made records for further statistical analyzing. The results showed that:the logarithmic average of Aerobic plate count (within2million CFU/mL) is4.832with a standard deviation of0.869. Milk production(P<0.01) and stage of lactation(P<0.01) exerted highly significant impact on Aerobic plate count; Body condition score, milk production, stage of lactation, parity and udder had no significant effect (P>0.01) on total number of coliform number; Aerobic plate count and Total number of Coliform Group reached a valley value with a body condition at3.25; Aerobic plate count and Total number of Coliform Group were ideal in Mid-lactation cows; When parity increased, Aerobic plate count and Total number of Coliform Group followed an upward trend; Lower Aerobic plate count and Total number of Coliform Group occurred in Medium-yield cows; the front of the breast area had higher values in Aerobic plate count than the rear; the left mammary udder had higher Total number of Coliform Group but lower coliform number than the right.2.347Samples across four seasons were collected from107milking cows of a Yangzhou Dairy farm, with the sampling under the same lactating period as possible. In accordance with the national standard method, we measured enviromental bacterial number, total number of Aerobic plate count and Coliform Group in milk, and explored the enviromental impact on total number of Aerobic plate count and Coliform Group in milk. The results showed that:season and feeding mode affected extremely significantly on Aerobic plate count (P<0.01); season, enviromental bacteria number and feeding mode affected extremely significantly on total number of Coliform Group (P<0.01). The enviromental bacteria number, Aerobic plate count and total number of Coliform Group in milk in the loose housing system were lower than in the tethered system.3.434milk samples were collected from a total number of107dairy cows in a dairy farm in Yangzhou across four seasons for BMT and bacteriological detection during2012and2013. The effects of mastitis situation on Aerobic plate count and Total number of Coliform were then analyzed. The results showed that:85of the434udders (19.59%) were infected mastitis, with an incidence of22.13%of forward-left udders,17.97%of forward-right,14.29%of hind-left and23.0%of hind-right. The incidences of spring, summer, autumn and winter were15.46%,16.33%,24.82%and14.7%, respectively. The highest incidence appeared in fall with the lowest incidence in spring. With the increase of mastitis degree, Aerobic plate count and total number of Coliform Group in milk increased, with a significant difference in Aerobic plate count for different degree of mastitis (P<0.01)4. The relationship of the content of endotoxin with Aerobic plate count in raw milk and pasteurized milk was explored using immunological LAL gel method. The results showed that, Aerobic plate counts of most of the samples were below two million CFU/mL, with a surpass rate of3.92%, with a universal existence of endotoxin in raw milk. After the pasteurization at a medium temperature for a long time, the content of endotoxin in milk increased significantly, demonstrating that the endotoxin level correlated positively with the Aerobic plate count in raw...