Bacteria plate counts in discard milk can range from similar to whole milk to several hundred fold higher than that of whole milk. High bacteria counts may cause symptoms from mild digestive upset to more serious health concerns. In addition, producers now have diseases like Johne’s to consider.
Because of these issues, producers are beginning to look at pasteurization as a way to provide a safe healthy product to their young calves. Pasteurization does not sterilize the milk, but rather reduces pathogens to levels that eliminate risk of infections from feeding pasteurized milk to calves.
Pasteurizers come in two common types, batch and continuous flow. Batch pasteurizers heat the milk to 145 degrees F and hold it at that temperature from at least 30 min. These pasteurizers work well on herds of modest size. Larger herds typically use continuous flow, also known as High Temperature, Short Time (HTST) pasteurizers. In HTST pasteurizers, milk is rapidly heated to 161 F and held for 15 sec.
In all cases, pasteurizers need to have a good source of hot water, and need to be cleaned and maintained on a regular basis. Growers should take these operation and maintenance cost in to consideration when making a decision on purchasing a pasteurizer.
Collected milk should be pasteurized as soon as possible to avoid a rapid increase in bacteria numbers. If milk cannot be pasteurized immediately, milk should be cooled to slow growth in bacteria numbers.
After milk is pasteurized it should be fed as soon as possible to avoid recontamination by bacterial organisms. Milk should be stored in clean, closed containers to avoid contamination and all equipment (storage tank, buckets, bottles, nipples, etc) needs to be sanitized.
Finally producers should monitor quality of pasteurized milk by routinely culturing samples (Goal: <20,000 cfu/ml), testing for alkaline phosphatase (enzyme destroyed at pasteurization temps), and having milk samples tested for fat%, protein% and other solids to determine the amount of variation in nutrient content.