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|Dairy basics - Calf and Heifer Raising|
|Written by Jim Quigley|
|Thursday, 25 August 2011 13:57|
Pasteurizing whole milk has reduced the risk of infection in people and, doubtless, saved millions of lives all over the world. The word “pasteurizing” comes from the name of the inventor, Louis Pasteur, who invented the method of heating milk to kill pathogens and improve human health.
On the dairy and calf ranch, pasteurizers are becoming more popular to improve quality of waste milk for calves. These units are generally large enough to pasteurize all the waste milk fed to calves – often hundreds or thousands of liters.
More recently, commercial colostrum pasteurizers were introduced to the market. These units pasteurize smaller batches of colostrum with minimal risk to the colostrum or calves consuming it. This article will address some of the pros and cons of these pieces of equipment.
Recent developments with other forms of pasteurization, which include ultraviolet radiation (UV) and chemical “pasteurization” (e.g., treatment with formic acid), will not be addressed in this article.
Kinds of pasteurization
Often, the proteins in colostrum “cook” and, in turn, plug equipment and turn into a sticky mess that is difficult and aggravating to clean. Thus, HTST pasteurization is not used with colostrum. Rather, we turn to batch pasteurization.
Batch pasteurization of colostrum requires that the colostrum be heated to 60°C (145°F) for 60 minutes. Both parameters must be followed carefully. Colostrum appears to be both time and temperature sensitive.
Research conducted at the University of Minnesota suggests that holding colostrum at 60°C for 60 minutes effectively kills Mycobacterium avium subsp. paratuberculosis, the organism that causes Johne’s Disease.
Pros of pasteurization
• Bacteria reduction. The most obvious value to pasteurizing colostrum is to reduce bacterial counts. More and more research suggests that bacterial contamination in colostrum is a huge problem on dairies. This is particularly true for colostrum stored in the refrigerator or freezer.
The combination of suboptimal collection methods, poor sanitation of collection and feeding equipment and improper storage results in total plate counts (TPC) exceeding one million in many tested samples.
• Proper pasteurization dramatically reduces bacterial load in colostrum, which is important to minimize risk of infection with organisms such as E. coli, rotavirus and other pathogens. Note that these pathogens can remain a problem even when colostrum is pasteurized – these organisms can also infect the calf after the first 24 hours of life.
• Improved efficiency. Several recent research studies have shown that pasteurizers increase the apparent efficiency (AEA) of IgG absorption in newborn calves. The AEA in colostrum is the calf’s ability to absorb ingested IgG into the bloodstream. It is measured by sampling blood of a calf at 24 hours of age and comparing the total number of grams of IgG in the serum divided by total grams of IgG intake.
Typical AEA for maternal colostrum ranges from 20 to 35 percent. Pasteurizing colostrum appears to increase the AEA by 2 to 3 percent compared to non-pasteurized colostrum. Thus, calves fed pasteurized colostrum will have higher serum IgG concentration compared to calves fed unpasteurized colostrum with similar IgG.
Cons of pasteurization
• Garbage in, garbage out. Pasteurization is not sterilization! Pasteurizing colostrum will certainly reduce total bacterial counts, but it doesn’t eliminate bacteria completely. Colostrum highly contaminated will be improved, but if it’s garbage (loss of protein through bacterial fermentation, lower pH, loss of glucose, etc.,) it will still be garbage (albeit with fewer bacteria) after pasteurization.
Too many producers (and vets and nutritionists) consider pasteurization to be a panacea – it is not. Changes in colostrum composition caused by bacterial contamination are not undone by pasteurization.
• Pasteurizing kills leukocytes. Colostrum contains a huge number of immune cells called leukocytes. These immune cells are thought to contribute to the immune system of the calf when fresh colostrum is consumed. Some researchers have shown improved health and resistance to enteric infection when colostrum contains these viable leukocytes.
Colostral leukocytes are sensitive to heat and are killed when colostrum is pasteurized. However, freezing kills them too. Many calves are routinely fed frozen/thawed colostrum without apparent ill effects. Thus, these viable leukocytes may be valuable to the calf, but processing to reduce bacterial counts may outweigh that value.
• Unknown effects on other proteins. Heat kills colostral leukocytes. Some research suggests that pasteurizing colostrum may denature important proteins in colostrum. Current research here is scanty, particularly in cows. More research is needed to determine which proteins in colostrum make an important contribution to calf health and the effect of pasteurization on them.
• Maintenance of equipment. Like every piece of equipment on the farm, the pasteurizer must be regularly maintained. Manufacturers provide a maintenance schedule – it should be followed closely to ensure the equipment functions properly.
Also, calibrate! Regularly use an accurate thermometer to test the pasteurization temperature. It’s important to be sure there isn’t “drift” in the electronics of the machine.
• Initial cost. Pasteurizers cost money to purchase and maintain. Initial outlays are generally in the $5,000 to $15,000 range, depending on the size of the unit. This may not be a big investment in the scheme of dairy farms, but this is a very specialized piece of equipment that should be only for pasteurizing colostrum.
• Labor. Using a pasteurizer requires that the workers using the unit be properly trained on how to properly collect, pool, pasteurize and store pasteurized colostrum without causing the “garbage in, garbage out” scenario. While most units are simple to operate, the maintenance and management of unpasteurized and pasteurized colostrum can be complex and laborious.
• Does not fix low IgG. A major problem with colostrum quality – low IgG concentration – is not solved by using a pasteurizer. As we all know, some cows produce colostrum that contains too little IgG, and calves are at a real disadvantage when fed this product.
Pasteurizers, when used properly, have little effect on IgG. If temperatures used in the pasteurizer are too high, IgG concentrations in colostrum can be reduced, exacerbating the problems with low- IgG colostrum. In this situation, use of a colostrum supplement or colostrum replacer is essential to ensure the calf consumes a sufficient mass of IgG.
Pasteurizers can be a valuable adjunct to good colostrum management. But remember, buying a piece of equipment will not solve an underlying management or training issue. PD
Pasteurizing colostrum can improve calf management by reducing the risk of infection and improving apparent efficiency of the colostrum. Photo by PD staff.