WildAgain Wildlife Rehabilitation, Inc.

(Excerpted from: Manufacturing Changes for Esbilac® Powder Affect Wildlife Rehabilitators. 2010.
 Allan M. Casey, III and Shirley J. Casey, WildAgain Wildlife Rehabilitation, Inc., Evergreen, CO)


Manufacturing Changes for Esbilac® Powder Affect Wildlife Rehabilitators - Questions and Test Results

Allan M. Casey, III and Shirley J. Casey


This new report sheds light on problems experienced by wildlife rehabilitators who fed formula made with Esbilac® powder last year, as well offering suggestions about how they may be able to use it with better results. The research, by Allan and Shirley Casey of Colorado, suggests a decrease in solubility, among other issues, may have caused gastrointestinal and growth problems seen in squirrels, opossums and other wildlife species.

Esbilac® powder, a milk replacer designed for puppies, is manufactured by PetAg of Hampshire, IL. The powder is commonly used as a base for milk-replacer formulas fed to orphaned wild mammals in rehabilitation, sanctuaries, and zoos. The problems surfaced after the company changed their drying process in December 2008. As a result of the new process, the powder no longer dissolved as easily when mixed with warm water and used immediately.

More on Mammal Nutrition

More resources are available for viewing or downloading. Click here for an easy-to-use listing of the various web pages and reports. Many include photos, charts and resource lists.

A dozen other powdered milk replacers are currently being tested for ingredients and solubility, including KMR®, GME®, Zoologic® 33/40, Fox Valley®, 21st Century®, and Farnam's Just Born®  This report is available here.

The authors found that mixing the powder with very hot water, adding fats and probiotics and letting it sit in the refrigerator for at least four hours before using appears seems to help solve many of the GI problems that resulted in sickly wild mammals last summer. The fats were added to make the formula more closely resemble mother’s milk from squirrels, raccoons and rabbits. The probiotics helped break down milk proteins, making them easier to digest, as well as improve overall digestion and GI health. 

Photos in the report show that the formula mixed with warm water and a quick stir, as directed on the label, separated after 20 minutes. The top layer had not dissolved as consumers expected. Photos of the microscopic examination of the formula confirmed solubility changes. Young animals that eat an inadequately dissolved formula are consuming less nutrition and can develop diarrhea and grow more slowly. The inadequately dissolved and undigested milk products in an animal’s GI tract are a great place for bacteria to grow – and infections to develop.

Other differences with the ‘new’ Esbilac® powder that can influence nutrients and calories are also described, such as compaction in the can and less weight than previous powder. This report focuses on the impact of the changes in Esbilac® powder on wild mammals, not puppies. PetAg says problems have not been reported for puppies.

Begin reading the report below or click the following links to download a short or full version.


Click here for the shorter version of this report (PDF 1.5 MB)

Click here for the complete, longer version (PDF 2.7 MB)

Sections of the Report

1.) Background (see below)

2.) Questions and Test Results

- Question #1 - Does the 'new' Esbilac® powder consistently meet the Guaranteed Analysis minimums for protein and fat? Have the minerals changed?

- Questions # 2 & 3 - Has the weight of the product changed? Does the product have uniform density, or is it subject to compaction that can affect measurement?

- Question #4Is the product still a quick mix? Are changes needed to rehydrate into a formula?

- Question #5 - Is rancidity an issue?

3.) Implications and Suggestions: What does this mean for wildlife rehabilitators?

4.) Considerations for preparing formula with milk replacer powders for wild mammals

5.) References and Resources


Background - Unexplained problems emerge during 2009

A few wildlife rehabilitators began reporting unexplained health problems with young wild mammals in the spring of 2009. Those cases and reports increased as the year progressed. After eliminating other more common causes such as overfeeding and endoparasites, they realized a common element was that these juvenile wild mammals were all being fed formula made with PetAg’s powdered Esbilac® puppy milk replacer.

Medical conditions in some juvenile wild mammals after being fed formula made with the 'new' Esbilac® powder:

Early conditions (more common)
- Bloat,
- Soft stool and diarrhea,
- Slow growth, dehydration
Later conditions (fewer animals)
- Urinary tract infections
- Gastroenteritis and intestinal scarring
- Liver and/or kidney damage
- Pneumonia
- Metabolic Bone Disease
- Emaciation 
Examples of diarrhea that developed in  juvenile squirrels after they were fed formula made with the 'new' Esbilac® powder in autumn 2009.

These rehabilitators contacted PetAg, the manufacturer of Esbilac® powder, to ask about any recent changes. PetAg revealed it had recently switched from using a multi-step drying process to a single-step spray-dry process. This change was described as the type of operational adjustment companies often make, and which is often unnoticeable to consumers. PetAg representatives assured rehabilitators that the Esbilac® powder was the same recipe, contained the same ingredients, and had no change in formulation. They said it still met the Guaranteed Analysis on the Esbilac® label.

PetAg did, however, acknowledge some difference in weight, texture and mixing. First, per any given unit of volumetric measure, the powder weighed slightly less than before. Second, because the powder showed a tendency to be more compact in the bottom of the can than at the top, PetAg suggested that customers turn the can over several times to aid in a more even distribution before measuring the powder prior to use.  Third, the company mentioned that the ‘new’ Esbilac® powder was no longer as quick to mix, and suggested that customers use hotter water and stir a little longer than previously. However, these instructions were not on the label, so unless customers called and spoke with the PetAg staff, they would not have known about those handling and mixing changes.


Rehabilitators report mixed results

Some wildlife rehabilitators continued to see positive results with Esbilac® powder, consistent with prior years. Others reported an increasing number of cases of gastrointestinal and other health problems, including some fatalities, when using the ‘new’ Esbilac® powder. Species affected included juvenile squirrels, chipmunks, opossums, cottontail rabbits and raccoons. The problems included soft stool, severe diarrhea (often green in color), slow or no growth, ravenous appetite, dehydration and emaciation.

Healthy Eastern gray squirrel fed formula made with  the 'old' Esbilac® powder. Photo provided by L. Ricketts, ME. This juvenile Fox squirrel developed severe diarrhea and secondary infections, and was unable to gain weight when fed formula made with 'new' Esbilac® powder in autumn 2009. Photo provided by T. Muzik, CA. Juvenile Western Gray squirrel developed severe bloat, diarrhea, and secondary infections with high fever when fed formula made with the 'new' Esbilac® in autumn 2009. Photo provided by T. Muzik, CA.

Medical tests and necropsies reported to WildAgain revealed massive infections due to abnormally and significantly elevated levels of Escherichia coli (E.coli) and Klebsiella pneumoniae (Klebsiella p.). Some animals also had Salmonella, Staph simulans, and Strep agalactiae. In addition, some tests showed the presence of the protozoan Cryptospodium. These infections could have been primary or secondary conditions. Bacterial culture and sensitivity results revealed that some of the infections were antibiotic resistant. Urinary tract infections, gastroenteritis, rectal prolapse, pneumonia, intestinal scarring, enlarged livers and kidney damage were also reported. While some of the animals recovered after medical treatment and changes in diet, others did not.


Research on the changes in the new Esbilac® powder

Even though PetAg indicated the Esbilac® formulation, ingredients and Guaranteed Analysis had not changed, some rehabilitators began to investigate whether and if so how changes in the Esbilac® powder might have caused the problems. Some of the independently performed Typical Nutrition Analyses (TNA) confirmed what PetAg had previously reported. Other research showed the ‘new’ Esbilac® powder produced with the single-step spray-dry process had physically changed (e.g., different texture) and performed differently (e.g., needed hotter water for mixing). The research began to offer insights as to why some rehabilitators had seen positive results, while others saw some juvenile wild mammals become ill and die when they used the Esbilac® powder made with the single-step spray-dry process.

PetAg had stated the product was free of contaminants or toxins such as melamine, which had been responsible for massive milk and pet food recalls in 2007. Further, PetAg certified that the Esbilac® powder was not rancid and did not contain bacteria when it left its manufacturing facilities. Several rehabilitators sent the ‘new’ Esbilac® powder to certified independent laboratories for a variety of tests, including bacteria and melamine. The results shared with WildAgain were negative for bacteria and contaminants, including melamine.

A few rehabilitators returned Esbilac® powder fed to animals that became ill to PetAg for additional testing in autumn 2009. In response to a WildAgain request, PetAg reported in January 2010 that those samples had tested negative for bacteria and rancidity.


Questions pursued by WildAgain

WildAgain has had many conversations with rehabilitators, veterinarians, food scientists and professional animal food nutritionists about the potential differences in the two Esbilac® powders. WildAgain has focused efforts to answer the following questions regarding the new single-step Esbilac® powder:

1.)     Nutrient composition – Does the ‘new’ Esbilac® powder consistently meet the Guaranteed Analysis minimums for protein and fat? Have the minerals changed?

2.)     Physical properties: weight – Has the weight changed and if so, by how much?

3.)     Physical properties: density – Does the new product have uniform density, or is it subject to more compaction than the prior multi-step dried product?

4.)     Solubility – If the product is no longer as quick a mix, what changes are needed to rehydrate and dissolve the ‘new’ Esbilac® powder?

5.)     Stability – Is rancidity an issue?


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