Foodborne Pathogens Can Lurk Around the Farm Environment
Foodborne pathogens can be found throughout the farm environment in manure, bedding, and animal feed, including silage. The possible presence of these disease-causing microorganisms is a concern for all dairy producers, but farms with value-added dairy businesses should be extremely vigilant. With changes in consumer purchasing habits, uncertain milk markets, and an interest in viability and sustainability, some farms have turned to value-added enterprises. These ventures include direct milk sales in states where permitted, processing cheese on the farm, and agritourism. Farm entrepreneurs can feel more confident in the safety of their products by recognizing sources of pathogens and understanding how to minimize contamination risks.
Silage can be a potential source of pathogens harmful to humans and animals. However, implementing good silage management practices can minimize exposure. Examples include harvesting at the right time, properly functioning equipment, packing and covering the storage structure to exclude oxygen, possibly using inoculants and additives to aid in fermentation, and having employees follow safety protocols. Additionally, traffic control on the farm to prevent cross-contamination and restricting access to protected feed or calf areas can limit the spread of pathogens. Good hygienic practices especially when feeding and milking are encouraged.
A foodborne pathogenoften associated with silage is Listeria monocytogenes (Driehaus et al., 2018). This persistent pathogen is a nemesis of food processors. Humans and animals can experience serious health consequences, including death, due to this organism. L. monocytogenes has been isolated from various environmental sources, including soil, water, and manure. Forage crops ensiled by wrapping, bagging, or storing in bunker silos can potentially be contaminated. When conditions are favorable for L. monocytogenes, such as when silage has fermented poorly, bacteriamay multiply rapidly (Queiroze et al. 2018). Attention to the ensiling process to decrease pH and exclude oxygen will limit the resources available to bacteria for survival and growth. Anytime new material is added to a storage structure, it is an ideal time for harmful bacteria to multiply due to exposure to oxygen and elevated pH before fermentation. Most pathogenic microorganisms need specific conditions to grow, including a food source, the proper pH, moisture, time, and a specific temperature range. Some also need oxygen, while others do not or require only a limited amount. Pathogens can be reduced or eliminated by depriving them of the resources they need to survive. Pasteurization or other lethality treatments of milk and dairy products, such as acidification or drying, reduce or eliminate the risk due to pathogens.
Poor-quality silage has been reported as a factor in the contamination of raw milk, related to cow cleanliness and fecal bacteria (Sanaa et al., 1993). A thorough udder preparation routine prior to milking can reduce the possibility of milk contamination, as well as feeding good-quality silage. Value-added processors need to be aware ofL. monocytogenes's ability to survive refrigeration temperatures and potentially cause problems if post-processing contamination occurs. To prevent cross-contamination of the processing environment and food products, implement and reinforce good hygiene practices. Limit access to the processing facility to avoid carrying the pathogen into the environment on clothes or boots. Enforce a policy that restricts farm personnel from entering the processing facility after being around silage. Develop and implement a thorough sanitation program for the processing area, and conduct routine monitoring to ensure its effectiveness.
L. monocytogenes can be found throughout the farm environment. An association between poor ensiling practices and pathogenic bacteria has been demonstrated; be prepared for harvest and implement a plan to make good-quality silage. Minimizing the risk of illness from L. monocytogenes and providing a safe, high-quality product should be a goal for all dairies, including value-added enterprises.
References
Driehaus F, Wilkinson JM, Jiang Y, Ogunade I, and Adesogan, AT. 2018. Silage review: Animal and human health risks from silage. J Dairy Sci 101:4093-110.
Queiroz OCM, Ogunade IM, Weinberg Z, and Adesogan, AT. 2018. Silage review: Foodborne pathogens in silage and their mitigation by silage additives. J Dairy Sci 101:4132-42.
Sanaa M, Poutrel B, Menard JL, and Serieys, F. 1993. Risk factors associated with contamination of raw milk by Listeria monocytogenes in dairy farms. J Dairy Sci 76(10):2891-8.
