On-Farm Pasteurized Milk Fed To Dairy Calves - Association Of Bacteria Counts Following Pasteurization With Season, Temperature And Time Until Feeding
David J. Wilson*, Gregory M. Goodell and Tessa Kelly
Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT 84341 (Wilson), and the Dairy Authority, Greeley, CO 80634, USA
- *Corresponding Author:
- David J. Wilson
Department of Animal
Dairy and Veterinary Sciences, Utah State University
Utah Veterinary Diagnostic Laboratory
950 East 1400 North, Logan, UT 84341, USA
E-mail: [email protected]
Received date: August 03, 2012; Accepted date: October 20, 2012; Published date: October 22, 2012
Citation: Wilson DJ, Goodell GM, Kelly T (2012) On-Farm Pasteurized Milk Fed to Dairy Calves – Association of Bacteria Counts Following Pasteurization with Season, Temperature and Time until Feeding. J Vet Sci Technol 3:124. doi:10.4172/2157-7579.1000124
Copyright: © 2012 Wilson DJ, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
On-farm pasteurization of waste milk fed to calves has become increasingly common over the last 15 years. This study investigated bacteria counts in milk before pasteurization and for 24 h following pasteurization at varying storage temperatures associated with seasons. Standard plate counts on Aerobic Count Plate PetrifilmTM to enumerate bacterial colony concentration were measured on raw and post-pasteurized milk after pasteurization at 63°C (145°F) for 30 min using commercial pasteurizers on 3 different commercial dairy farms. Each farm was sampled in each of 4 seasons of the year. All 12 batches of milk were divided into 2 aliquots. One aliquot was incubated at controlled temperature to mimic the season (refrigerated, room temperature, or incubated at 37 °C) and the other was incubated at ambient outdoor temperatures. The SPC was determined at pre-pasteurization, 0 (immediately post-pasteurization), 1, 2, 3, 4, 5, 6, 7, 8, 10, 12 and 24 h post-pasteurization. The final general linear model testing for factors associated with LogSPC was highly explanatory (R2=0.71), and significant (P<0.0001). This final model for LogSPC included time since pasteurization, season, farm, the interaction of time and season, and the interaction of season and farm. The model showed that passage of time was associated with increased LogSPC, especially during summer. In a northern temperate climate under the conditions observed during this study, milk - could safely be fed-if defined as SPC<20,000 cfu/ml-for at least 8 h post-pasteurization during fall and spring, and for 24 h during winter, but only for 3 h if milk was stored outside during the summer. These results suggest that for milk kept outdoors during summer, any milk remaining after first feeding following pasteurization should not be fed to calves at subsequent feedings, but instead should be re-pasteurized or discarded.