Powdered Milk Replacer Analysis - Summer 2021 Update

3) What do the test results reinforce and confirm what do we still not know?

 

Higher moisture content in Fox Valley products. With remarkably and consistently higher Moisture levels (and thus lower Total Solids levels) it remains unclear as to the cause and/or intent of such a marked change across all Fox Valley product lines in the recent round of tests.  

 

While considered unlikely, an increase in moisture in a milk powder could allow bacteria to grow more readily. WildAgain did not arrange for testing for bacteria since we did not anticipate an increase in moisture in the milk powders that exceeded the guarantee level to such a degree (>5%). Such tests could be conducted by the laboratory if future factors suggest possible bacterial contamination, concerns develop, and resources are available.

 

High levels of Protein. The level of proteins in Fox Valley and Esbilac® powders continue to test much higher than the GA. Milk proteins are composed of mostly casein and some whey which are separated when processed. Since most of the separated whey is preferred for human supplements, milk powders produced for animal consumption include more of the separated casein, including milk replacers for pets and wildlife. Casein is more difficult to reconstitute then whey. Might that have caused the sludge-like consistency that was reported? Rehydrating dried casein requires a more complete reconstitution process to make it easier to digest and utilize, especially for younger wild mammals with less developed GI systems. Since casein is harder to digest and doesn’t reconstitute as readily, could higher concentrations of casein cause or contribute to the reported digestive issues?

 

Unexpected results could occur when the protein in the formula exceeds the GA by an unexpected amount. The formula may appear thicker when mixed, especially if it is not fully reconstituted. Feeding a higher percentage of protein to an infant, than contained in the species milk, could strain the kidneys.  This also could add nitrogen in the liver, making it work harder to process waste and toxins, and more. A neonate animal could have difficulty digesting extra protein if a milk powder is inadequately reconstituted.  This could cause them to possibly develop GI disorders and have a slower growth rate if unable to adequately digest and use the protein. It must be noted that such health conditions may be caused by other factors as well. 

 

Increasing levels of Fat closer to the GA value (plus GME rancidity issues). With overall fat content increasing as discussed above, formula recipes may need some fine-tuning versus what was successful in the past, especially with Fox Valley products. This will certainly have to be examined at the individual product level. 

 

Rancidity is an ever-present concern with products that contain high fat levels. Those that contain vegetable oils that have high levels of polyunsaturated fatty acids are most prone to oxidation and development of rancidity, such as with soybean oil (61%). Since GME lists soybean oil as its third most predominant ingredient, that could be a contributing factor to the rapid onset of rancidity in that milk replacer. Most of the other products list ‘vegetable oil’ as the primary source for fats. Unfortunately, with such a non-descript and generic term to describe the source and relative mix of the oils, it is impossible for the user to determine which specific plant-based oil is contained in the product and if it may have a high susceptibility to oxidation and rancidity (USDA database indicates 41+% of polyunsaturated fatty acids in vegetable oil – NFS (not further specified). Proper storage practices are necessary to mitigate the onset of rancidity.

 

Carbohydrate levels are declining. Formula recipes need to be re-evaluated to insure appropriate carb intake due to the decline in relative carb concentrations (again, WildAgain’s Calculator incorporates these variations). Most of the mothers’ milk studies indicate a carbohydrate level of .5 to 5.0% in the form of lactose (a disaccharide made up of glucose and galactose). Glucose is the only form of energy used by the brain. An inadequate amount of glucose in the blood and carb stores (in muscles and the liver) can lead to muscle fatigue and lack of concentration. Carbs are important for hormonal regulation. Lastly, as the primary energy source for the body, a lack of adequate carbs in the diet may likely compromise or restrict muscle, tissue, and skeletal development in young, growing animals.

 

Fiber Content. It bears repeating that powdered milk, like all foods derived from animals, does not contain fiber. As shown in the charts above, the fiber content is now averaging just under 2% for all products tested, with about 40% less in the PetAg products. While its presence is still unclear (GA at 0%), it has dropped significantly from prior years and appears to be stabilizing at current levels.

 

Ash Content. There has been little change from prior years. If one or more of the products have been used in formula recipes in the past, there is little reason to believe that any digestive or growth issues are attributable to the quantity of minerals in the products. That said, quality issues have arisen lately, such as the dicalcium phosphate (DCP) issue in Esbilac®, which PetAg disclosed and corrected. If there is concern over the quality of the minerals, outreach to the manufacturer to provide feedback is warranted and advisable.

 

Calcium, Phosphorus and the Ca:P ratio. These primary dietary minerals and their ratio all appear to be within the accepted reference range, except for GME, which continues to test at low concentrations of both calcium and phosphorus. It also appears from recent testing that concentrations are increasing slightly in the long-term trend.

 

A few more product specifics.

 

- Fox Valley 38/47. Tested at 34/44. Lower than the GA on Protein (-9.4%) and Fat (-6.8) and higher on Moisture GA by 27%. 

 

- Fox Valley 40/25 ‘Brown Specks.’ Visible as shown above and appear to be larger particles relative to the rest of the product. Clearly gets trapped by a 500µm sieve. (500µm = 1/2mm). Composition, origin and effects of using are unknown.

 

- Fox Valley 40/25. The purpose of the new ‘bubble gum’ and ‘banana’ scented flavorings is unknown. Apparently, there is an option to order the product without these additives if there is concern with any possible negative effects of feeding it.

 

- Fox Valley 40/25 and 32/40. The sludge at the bottom of a mixing container has not been observed previously and cause is unknown. Perhaps this is caused by a change in the type of dried casein contained in the product, which is typically the ingredient that is most difficult to reconstitute. Otherwise, the origin is unknown. 

 

 

4) Are there action steps that we should consider?

 

√ Buy fresh and follow good storage practices. Before anything else, make sure that the powdered milk products to be used in formula recipes are purchased as soon after the manufacture date as possible. Ask the vender to provide lot numbers and dates to assess the date of manufacture. Then properly store in a cool, cold, or frozen condition, depending on timing of impending use. While GME has been shown to be the most susceptible to oxidation and rancidity formulation, all of the milk replacer products carry the small risk of rancidity if not stored properly. Storing unopened, and especially opened, milk powder containers at room temperature or higher increase that risk.

 

The reconstitution properties of dried casein decrease over time as a function of any storage temperature. Colder storage slows this decrease in reconstitution efficiency. If the higher casein products have been stored improperly, even the best reconstitution techniques will be hindered and could result in the ‘sludge-like’ condition described earlier. 

 

The higher moisture in the Fox Valley products could provide a nutrient-rich medium for bacteria growth. Though unlikely in unopened containers, such contamination could occur if containers are left open.  Consider switching to a different container of milk replacer and arranging for the powder to be tested if unexplained bacterial infections develop in multiple small wild mammals being fed the same product

 

√ Return or discard products with off-odors or unusual/strange particles. Start by checking for freshness/off-odors and inspect for things that are unusual or do not look normal. If something does not look or smell quite right, consider a quick call to the vendor or manufacturer prior to use. They should have high interest if a product has been sold that fails to meet their internal quality control standards. Ask other rehabilitators if they have had a similar experience. Return the product and ask for a replacement or refund, or discard if instructed to do so. If still unsatisfied, consider discontinuance of that product and consider alternatives. 

 

√ Consider using the WildAgain Formula Calculator for more current and precise lab-tested nutritional data than the required minimum/maximum GA values found on the label. As shown above, many of the milk replacer products are testing well above/below what the GA would ordinarily suggest. Several of the products have been at these higher/lower levels for many years. While some are still technically within guaranteed levels, perhaps using an “Expected Value” would yield more accurate calculations of the true amount of nutrients in a substitute milk formula. WildAgain’s Formula Calculator contains years of test data for most of the commonly used powdered milk products. Therefore, it makes the adjustment to a more actual Expected Value, rather than reliance on a GA, which tests have proven to be less accurate as to the contents in the container. The results of more recent lots of the products are being added from time to time, as in the case of the 30 lots added in June 2021.

 

√ Consider using multiple products to formulate a recipe. The old adage of “don’t put all your eggs in one basket” applies here and provides some common wisdom. If only a single powdered milk product is used in the formula recipe, the formula is totally dependent on that one single lot of that product. What if… that lot is an outlier in terms of nutrient composition vs the GA or Expected Value? Or it has not been stored properly and developed rancidity? Or it is deficient in a dietary mineral, such as Copper in many Fox Valley products? Or it has incorporated a lower quality of dried casein that is more difficult to reconstitute? 

 

A very simple and effective way to mitigate this ‘single product’ risk is to incorporate more than one milk replacer in the formula recipe. This approach also may provide a recipe that more closely matches the mother’s milk nutritional profile. Since each milk powder has its own relationship with water, reconstitute each powder separately and then combine when in final liquid form, in the appropriate amounts. 

 

√ Supplemental fats are probably still needed in some recipes. Some rehabilitators may wonder if supplemental fats are no longer required for some formulas to better match the species milk composition since the powders are currently testing higher than previous years. Others may be unsure of the effect on the recipe’s overall nutritional content from adding a certain fat additive in a specific amount. WildAgain’s Formula Calculator incorporates current test results for these higher fat levels for products that have been lab tested. The Formula Calculator provides a quick and easy way to evaluate previously successful recipes to determine if any changes are needed for continued supplementation options (types and amounts) to address fat deficiencies. 

 

√ Dietary mineral supplementation (esp. Ca) is probably unnecessary. The test results and the charts above show that concentration levels for Calcium and Phosphorus consistently fall within the acceptable range, except for GME. The same is true for the Ca:P ratio. If a concern exists that one product has either too much or too little of one of the minerals, a blending approach easily evens out any high or low values and produces a more consistent product over time. 

 

Though some have discussed supplementing Calcium, these minerals are present in such minute amounts that it is very easy to inadvertently exceed an appropriate Calcium level. Additionally, it can very quickly result in an unacceptable Ca:P ratio. 

 

√ Reconstitute carefully and completely. Rehabilitators try to use the best products, construct a substitute milk formula recipe appropriate for the species, and follow an appropriate feeding protocol (e.g., amount per feeding, number of feedings per day). However, if the formula is not well prepared, the animal will not get the complete intended nutritional content or the full benefit of the formula. Effective formula preparation is essential, yet it is often underestimated and overlooked as a vital and key critical success factor in an animal’s diet. WildAgain offers a Formula Mixing Guide that incorporates a series of preparation steps that can help improve the chances of producing a well reconstituted formula that contains the nutrients in the carefully constructed recipe. Some of the suggested steps may be new to rehabilitators and differ from the instructions on the powdered milk labels. For example, the Guide incorporates weighing ingredients rather than measuring by volume (which can introduce a +/- 10% error in the intended amount of an ingredient). Additionally, it specifies adding the powder to warm water (110° F - 130° F) and allowing for some time for the powder to ‘wet.’ Next, since many of the milk replacers have poor wetting properties, more mechanical mixing is required well beyond a simple stir or shake. Most importantly, these powders reconstitute much more completely if allowed to rest in the refrigerator for at least 8 hours prior to use. Once reconstituted, a final combination of ingredients can successfully occur by adding other liquid ingredients, such as heavy whipping cream or another fully reconstituted powdered milk replacer, when included in a blended formula.