With the expansion of the size of individual dairy farms feeding waste milk from treated cows to bottle calves has become more common. Waste milk has the potential to have approximately 30% fat and 25-27% protein on a dry matter basis and therefore has the potential to provide a higher plane of nutrition than traditional 20% protein, 20% fat milk replacers. However, in contrast to milk replacers, waste milk may contain pathogens such as Salmonella, MAP (Johnes), and Mycoplasma that are detrimental to calf health. To overcome this concern, pasteurizers have been utilized to decrease the pathogen load fed to the bottle calves in the waste milk. Pasteurizer technology continues to improve, they must still be managed properly to produce the benefits for which they are purchased and installed. The following paper will summarize the benefits, concerns, and management issues that arise with the use of pasteurizers on our client dairies.
There are several general concepts that must be understood to maximize the benefit of a waste milk pasteurizer.
1. Pasteurization does not mean sterilization. We must continue to make this point to our clients. If the waste milk has a high degree of contamination, is improperly stored at high temperatures prior to pasteurization, or improperly stored from the time of pasteurization until feeding pathogen loads will be produced that even a properly functioning pasteurizer can't overcome.
In summary, pasteurizers allow for increased peace of mind when using waste milk to feed bottle calves. They can be of great value, but can also be the source of problems in a dairy farm's calf program. As with many areas of our client dairies, successful use of a piece of equipment or the implementation of a management program depends on how well they are managed. Once again, pasteurizers offer dairy veterinarians another area to get involved with on our client dairies. We can utilize our knowledge to help monitor for proper function and develop protocols that will maximize the value of pasteurizers to our dairy farmers and provide a valuable service to our producers.
2. Pasteurizers must be treated as if they are part of the milking system. Proper cleaning and disinfecting is a must if a pasteurizer is expected to provide its potential benefits.
3. Pasteurizers obviously do not alter antibiotic residues – this should be considered in the framework of what happens to calves when the leave the dairy.
4. Waste milk can be highly variable. This is true for milk components, milk quality, and availability. Strategies need to be in place to deal with these fluctuations. This could include solids testing combined with supplemental milk replacer to both make up for shortages in volume and for waste milk that is low in total solids.
5. Pasteurizers are available as both batch pasteurizers and HTST units. Batch pasteurizers may have "dead" spots if not properly agitated and may have difficulties incorporating automated cleaning, depending on size. A common recommendation for a batch a pasteurizer is to heat the batch to 145°F for 30 minutes. HTST have the positives of rapid heating and cooling and can be easily automated, but need adequate supplies of hot water. Additionally, the plates may become clogged. Common pasteurizer times for HTST units include 161°F for 15 seconds. The manufacturer should be consulted with on proper settings for optimal pasteurization.
6. Goals for the waste milk after pasteurization include standard plate counts of <20,000 cfu/ml and alkaline phosphatase activity of < 500 mU/ml
7. In addition to monitoring SPC and alkaline phosphatase activity, periodic cultures should be done to monitor the effectiveness of the pasteurizer to reduce or eliminate pathogens of concern on a specific dairy. An example of such a pathogen would be Mycoplasma.
8. The economics of pasteurizers can be very positive, although this depends highly on the value that is placed on waste milk.
9. New UV units show promise, but the sample size is still relatively small