All dairy farms have a supply of milk that is not saleable, typically referred to as waste milk. Waste milk may consist of excess colostrum, non-saleable transition milk from the first six milkings, abnormal milk, mastitic milk and hospital milk including milk from antibiotic treated cows. Historically, raw waste milk has been fed to calves a means of economic efficiency and alleviating disposal challenges and associated environmental concerns. However, one major concern with this practice is that waste milk is often contaminated with potential pathogens. Bacterial counts in raw milk are variable and can be extremely high. The increased risk of transmission of infectious pathogens shed directly from the mammary gland can pose serious health issues with the animal. Bacteria load can proliferate due to post-milking contamination (e.g. manure) and milk that is not collected, stored or cooled properly. These concerns of bacterial contamination with Salmonella, Lysteria monocytogenes, E.coli, Mycobacterium paratuberculosis (the organism responsible for Johnes disease), etc. through feeding waste milk have led to a general recommendation not to feed waste milk to calves.
Pasteurization of waste milk for calves is one option to reduce the transmission of disease to calves. The heating of milk to a specific temperature for a specified time has been used to destroy pathogenic bacteria and reduce spoilage bacteria to negligible levels. While pasteurization destroys major pathogens, it does not sterilize milk and some spoilage bacteria may survive. Temperature and time should be carefully monitored during the pasteurization process. Standard written protocols should be set up for using and maintaining waste milk pasteurizers.
Feeding pasteurized waste milk has been demonstrated to improve calf health as compared to feeding raw waste milk. Waste milk is pasteurized to destroy pathogens and reduce the risk of disease transmission to calves. Research trials have shown that feeding calves pasteurized milk lessens the severity and duration of scours and pneumonia when compared to calves consuming non-treated milk. Also, average daily gains are significantly greater with pasteurized milk when compared to raw milk. Other related advantages include fewer sick days, lower mortality rates, lower health associated costs and higher weaning weights.
When Feeding Pasteurized Milk A pasteurized milk feeding program requires more intensive management than a milk replacer feeding program. Initial capital costs are significant and hot water capacity is critical. A separate designated hot water source to accommodate the pasteurizer may be required.
Success in a pasteurized milk feeding program is also related to the ability to control the milk before and after pasteurization. Time must be taken to clean the pasteurization equipment thoroughly and maintain the equipment for optimum operation efficiency. Poor cleaning procedures result in inefficient or ineffective pasteurization as milk protein, fat and inorganic films can buildup and interfere with heat transfer and may further inoculate milk with bacteria. Personnel capable of managing and monitoring the pasteurization system should be assigned the task of operating it.
The supply of non-saleable milk may not always be adequate to feed all calves. To be practically effective a dairy farm must have a stable supply of waste milk. Alternatively, dairy farm operators must have a strategy for periods when waste milk supplies are inadequate. Options may be using saleable milk, milk from higher somatic count cows or adding milk replacer solution to pasteurized milk.
Higher than required temperatures during the pasteurization process (the required time and temperature varies depending on whether the pasteurizing unit is batch or HTST continuous flow) actually makes the feeding value of the milk worse. When milk is overheated, the high temperatures can break down or denature milk proteins, rendering them indigestible to the calf. Indigestible proteins pass through the digestive tract and end up in the feces. Calves may actually become protein deficient, even though there was plenty of protein in the milk. Symptoms may be small, unthrifty calves with sunken eyes and rough hair coats. In batch pasteurizers, hot spots in milk can occur if agitation is not adequate or not functioning properly. Again, protein denaturing may arise.
Good management practices in the handling and storage of both pre-pasteurized and post-pasteurized milk should be adhered to. With pre-pasteurized milk, excessively high bacteria counts or inadequate cooling will cause milk to ferment and sour. Producers should not pasteurize soured milk because this can result in coagulation (curd formation).
Pasteurizers should be equipped to rapidly cool the milk after pasteurization is complete. Any remaining spoilage bacteria can double their numbers every 20 minutes at 38º Celcius. Post-pasteurized milk that is not being fed immediately should be chilled in a clean, covered container and later reheated to feeding temperature at feeding time.
Pasteurization provides no protection against antibiotic residues in waste milk and calves fed pasteurized waste milk may be contaminated with antibiotic residue, therefore producers need to consider appropriate meat withholding times. Post-pasteurization contamination of milk negates the advantages of the whole process so careful attention to regular and thorough sanitization of all milk holding, transfer and feeding equipment is required.
Heat Treating Colostrum
Untreated colostrum can pose a risk of exposing dairy calves to pathogenic bacteria when they are most vulnerable. Pasteurizing colostrum at temperatures traditionally used for pasteurizing milk presents two significant challenges. First, regular pasteurization temperatures have shown to decrease the availability of immunoglobulin G (IgG) resulting in lower serum IgG levels in calves that were fed pasteurized colostrums. Secondly, colostrum tend to thicken with increased viscosity as it is heated resulting in handling problems. More recent research has shown that these challenges may be overcome by heat treating colostrum using a lower temperature, longer time approach (e.g. 60º Celcius for 60 minutes instead of 63º Celcius for 30 minutes in a batch pasteurization system). Heat treating colostrum at temperatures above 60º Celcius will result in denaturing of IgG. Feeding heat treated colostrum to calves increases IgG absorption and serum IgG concentration when compared to feeding raw colostrum.
Success in pasteurizing milk is related to the ability to control the milk before and after pasteurization. When managed correctly, pasteurized milk is a calf liquid feeding option for larger farms. The main advantages are utilization of non-saleable milk and reduced disease transmission resulting in improved calf health and growth rates compared to calves consuming raw waste milk. Disadvantages include initial capital cost, required detailed pasteurization management, inadequate non-saleable milk supply and possible antibiotic residue concerns. Heat treating colostrum using a lower temperature, long time approach can be successful to reduce or eliminate major pathogens while maintaining available immunoglobulins and retaining physical fluidity for easier handling.
When compared to feeding raw waste milk to calves, the advantages of feeding pasteurized milk are clear. However, the feeding of premium quality milk replacers also offer several benefits including day to day consistency, ease and flexibility of storage, mixing and feeding along with good calf performance. Research has shown when calves are raised solely on premium quality milk replacer formulated with optimal blends of essential fatty acids and amino acids growth rates are improved. Equipment, space, time and handling requirements should be considered in evaluating the milk feeding program to use on your farm.
Akey Replacement Report; Milk Replacer Research, Comparison of Feeding Pasteurized Milk to an Akey and NRC Formulated Milk Replacer, Akey Nutrition and Research Center, Lewisburg, Ohio.
Akey Replacement Report; Research Review, Pasteurized Waste Milk, Akey Nutrition and Research Center, Lewisburg, Ohio.
A Review of Issues Surrounding the Feeding of Pasteurized Non-Saleable Milk and Colostrum; S. Godden, DVM, DVSc, J. Fetrow, DVM, MBA, DACVPM, J. Feirtag, MS, PhD, S. Wells, DVM, PhD, DACVPM, L. Green, MS, Center for Animal Health and Food Safety, University of Minnesota, St. Paul, Minnesota 55108
Feeding Heat-Treated Colostrum to Neonatal Dairy Heifers: Effects on Growth Characteristics and Blood Parameters; J.A. Elizondo-Salazar and A.J. Heinrichs, Department of Dairy and Animal Science, The Pennsylvania State University, University Park 16802
Heat-Treatment of Bovine Colostrum. I: Effects of Temperature on Viscosity and Immunoglobulin G Level & II: Effects of Heating Duration on Pathogen Viability and Immunoglobulin G; S. Goyal, USDA,ARS, National Animal Diseases Center, Ames, Iowa 50010, S. Godden, S. McMartin, J. Feirtag, R. Bey, J. Stabel, L. Metzger, J. Fetrow, S. Wells, H. Chester-Jones, University of Minnesota, St. Paul 55108
Glenn Smith, Dairy Nutritionist