Pasteurization of Waste Milk:
Calf Health and Production
Doug Hammon, D.V.M. Ph.D.
USU Extension Veterinarian
According to the 2002 NAHM's Dairy Survey, 87.2% of dairy operations in the United States feed waste milk to their heifer calves. While only 1% of all dairy operations pasteurized waste milk before feeding, 11% of large (> 500 head) heifer rearing operations feed pasteurized waste milk. Although feeding unpasteurized waste milk and colostrum is common, this practice may increase sickness and death loss in calves due to ingestion of disease causing organisms such as Salmonella spp., Mycoplasma spp., and Mycobacterium avium paratuberculosis (the bacteria that causes Johne�s disease). Dairy producers and calf growers are likely to continue to adopt pasteurization of the waste milk in the future, which in turn should reduce the risk of infection and death loss in calves. When weighing the benefits of waste milk pasteurization, producers often consider calf health and production, the economics of feeding milk replacers compared to feeding waste milk, and the cost of pasteurization. Several studies conducted over the past several years have focused on the effectiveness of waste milk pasteurization in destroying infectious agents and on the health and performance of calves fed pasteurized waste milk compared to raw waste milk and milk replacer.
Types of �on farm� pasteurizers
There are two types of commercially available �on farm� pasteurizers: batch pasteurizers and high temperature-short time (HTST) continuous flow pasteurizers.
Batch pasteurizers heat milk slowly to 145� F, hold it at 145� for 30 minutes, then rapidly cool the milk to feeding or storage temperature. Batch pasteurizers are generally easier to clean than HTST-continuous flow units. They should be equipped with an agitator to allow for even heating. The maximum volume of milk that can be effectively pasteurized is limited to about 150 to 200 gallons with on farm batch pasteurizers. Larger volumes require the use of HTST-continuous flow pasteurizers.
Commercial HTST - continuous flow pasteurizers. Milk is circulated through a network of heated coils, rapidly heated to 161� F, and held there for 15 seconds. Continuous flow systems should also be equipped to automatically cool the milk quickly to feeding or storage temperature. Continuous flow systems are generally more difficult to clean, requiring a cleaning procedure similar to that used in milking systems.
Effectiveness of Pasteurization in Destroying Infectious Agents
Laboratory studies have shown that pasteurization is effective in destroying bacteria that threaten calves. A University of Minnesota study included batches of saleable raw bulk tank milk and colostrum inoculated with E. coli 0157:H7, Salmonella sp., Listeria monocytogenes, and Staphylococcus aureus, which were pasteurized using two commercial on-farm pasteurizers; a batch model (Dairytech Inc., Windsor, Colorado) and a HTST model (Bettermilk Inc., Winona, Minnesota). Pasteurization with the batch unit destroyed all four organisms in both milk and colostrum. Pasteurization with the HTST unit either effectively destroyed or significantly reduced each of the four organisms in milk and colostrum. A recent study conducted at the USDA National Animal Disease Center showed that pasteurization of waste milk using a commercial on-farm HTST pasteurizer (continuous flow type pasteurizer) was effective in destroying 3 isolates of M. paratuberculosis, 3 serovars of Salmonella (derby, dublin, typhimurium); and 4 species of Mycoplasma (bovis, californicum, canadense, serogroup 7) at 2 different levels of experimental inoculation. HTST pasteurization was also effective in destroying M. paratuberculosis in experimentally inoculated colostrum. The results of this study suggest that HTST pasteurization is effective in generating a safer product to feed to young calves.
Calf Health and Performance
A study conducted in the mid 1990�s at the University of California-Davis estimated the contribution of pasteurization of waste milk and colostrum to gross marginal profit per calf at weaning and estimated the minimum number of cattle on a dairy farm for pasteurization to be profitable. This study indicated that calves fed pasteurized colostrum and waste milk were worth an extra $8.13 in gross margin/calf, compared with calves fed non-pasteurized colostrum and waste milk. This study concluded that an economic benefit was associated with feeding pasteurized colostrum and waste milk and that additional benefits may accrue, including higher average weight gain, lower death loss of calves, and fewer days in which calves are affected with diarrhea and pneumonia.
A recent field study conducted by University of Minnesota researchers compared two feeding programs: calves fed pasteurized waste milk and calves fed traditional 20:20 milk replacer. Waste milk from fresh cows (transition milk) and antibiotic-treated cows was pasteurized before each feeding using a commercial batch pasteurizer (Dairytech Inc., Windsor, Colorado). Calves fed pasteurized waste milk gained significantly more weight and were heavier at weaning (58.8 lbs gain; 147.3 lbs at weaning) than calves fed milk replacer (44.3 lbs gain; 134.0 lbs at weaning). Average daily gain was significantly greater in calves fed pasteurized waste milk (1.04 lbs/day) vs. calves fed milk replacer (0.76 lbs/day). Preweaning death loss rates were significantly lower for calves fed pasteurized waste milk (2.3%) than for calves fed milk replacer (11.6%). These researchers concluded that preweaning health and performance was significantly better in calves fed pasteurized waste milk as compared to calves fed a traditional 20:20 milk replacer feeding program.
Feeding waste milk is common in US dairy operations and is an economical practice for calf growers. However, feeding unpasteurized waste milk increases the risk of disease and death loss in calves due to ingestion of disease causing organisms. On-farm commercial pasteurization of waste milk offers a method for reducing this risk of infectious disease in calves.
On Farm Pasteurizers
Better Milk, Inc.
Goodnature Products, Inc.