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)          


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Question 1 - Has the nutrient composition of Esbilac® changed? Answer: Yes.


As mentioned, WildAgain was aware of several rehabilitators who had arranged for independent laboratories to conduct TNA for samples of Esbilac® powder to determine if Guaranteed Minimums were met. Some early initial reports indicated that fat levels were below the minimums. However, it should be noted that the type of test performed may significantly affect results and produce inaccurate values. For example, while an ether extract test is applicable for the determination of crude fat in dried forages and mixed feeds, it is not applicable for feeds containing heated dairy products (Association of Official Analytical Chemists). So while laboratories commonly use the ether extract test for many food products, that test can understate the correct fat values for heated products.

Figure 1. Esbilac® powder - Adherence to Guaranteed Minimums for Protein and Fat (as-is basis).

WildAgain arranged for a proximate analysis and mineral analysis, and specified the acid hydrolysis test for fat, which is better suited for testing heated dairy products. WildAgain submitted three samples of the old Esbilac® powder and six samples of the new Esbilac® powder from different lot numbers to a certified independent laboratory (Midwest Laboratories in Omaha, NE). The results indicated general adherence to the Guaranteed Analysis for protein and fat as published by PetAg and shown on the product labels. The results are shown in Figure 1, with the specific test results included in Appendix A (below). Additionally, while most all minerals appeared to be within acceptable levels, the concentrations of Calcium and Phosphorus in a reconstituted formula (mixed 1:2) have dropped by one-third and one-half, respectively. However, the Ca:P ratio seems to have actually improved (see Appendix B below).

Text Box: Figure 1
These tests show that the nutrient composition of Esbilac® powder has changed. While Guaranteed Minimums are generally being met (Figure 1), the relative values of the protein and fat have changed very slightly. The old Esbilac® had an average P:F ratio of .82 (within a range of .80 to .83 in the three samples tested). The new Esbilac® has an average P:F ratio of .84 (within a wider range of .78 to .88). In order to compensate for individual lots that have a higher P:F ratio, additional fats may need to be added to reestablish the prior P:F ratio. Since some juvenile wild mammal species require a milk composition with a higher fat content than is in pet milk replacer formulas anyway, wildlife rehabilitators may need to slightly increase the amount of fats. Tests of the ‘new’ Esbilac® also showed significantly more variability in mineral levels between individual lots (Appendix A below).


Appendix A - Product Testing

Tests requested for most samples included the following:

Proximate Analysis plus Minerals

Figure A-1. Esbilac® powder - Test Results for Proximate Analysis and Minerals.

Moisture, Crude Protein, Acid Hydrolysis Fat, Ash, Acid Detergent Fiber (ADF)

Minerals (Sulfur, Sodium, Potassium, Iron, Calcium, Manganese, Phosphorus, Copper, Magnesium, and Zinc

Peroxide Test (for rancidity)


A copy of all test results referenced in this document are available at the following links and are presented as received from Midwest Labs. Click on the specific lot number listed below:

     Lot E0487E (pdf)
     Lot J1168E (pdf)
     Lot L2758E (pdf)
     Lot 0759E (pdf)
     Lot 0919E (pdf)
     Lot 0929E (pdf)
     Lot 1639E (pdf)
     Lot 1649E (pdf)
     Lot 2049E (pdf)


Consistency of powdered Esbilac® between lot samples

A summary of the proximate analysis and mineral values for the 9 powdered Esbilac® samples tested by Midwest Laboratories, Inc. are presented in Figure A-1.

The tests of the 9 samples indicate that there has been a general decline in most components contained in the product since PetAg has moved to the single-step spray-dry manufacturing process. Exceptions are in protein and sodium, up 3% and 4% respectively. Moisture is also up (12%) which is somewhat questionable in a dry milk replacement powder. The changes in the average values are shown in the right hand column, with increases shaded in green and decreases in red.

Upon close review of the individual lot test results, it becomes apparent that the ‘new’ Esbilac® appears to be a far less

Figure A-2. Esbilac® powder - Consistency of product between lots sampled (Variance % from average).

consistent product from lot to lot. This is especially apparent for the various macro and trace minerals, when examining the relative variances from the average values for each mineral. The variance ranges as high as +82% and -58%. This compares negatively to the ‘old’ Esbilac® powder that had average variances generally with +/- 20%, as shown in Figure A-2 in the gray shaded area.



Midwest Laboratories

Testing of all product samples referenced in this document was arranged through Midwest Laboratories in Omaha, NE. Midwest Labs has serving the agricultural, industrial, environmental, and sampling needs of the United States and Canada for over 30 years.  Government agencies, such as the USFDA and USDA and official laboratory inspection teams regularly audit them to verify accuracy and quality of their procedures.  An extensive list of their qualifications and certifications is provided on their website. Midwest’s staff consists of over 100 scientists, lab technicians, clerical assistants, and administrative officers, housed in over 80,000 square feet of laboratory and support area. 


Pet food testing

Rehabilitators who wish to have any food products tested may contact certified independent laboratories. While such facilities may be found on the internet, there are benefits from asking nutritionists, food scientists and others about specific facilities. Since services, certifications, qualifications, experience, and prices vary, it is worthwhile to consider all of these factors rather than just selecting a lab that is nearby or less expensive.

Those interested in having tests conducted by Midwest Laboratories should call Sue Ann Seitz (Client Service Representative) at 402-334-7770 or email her at sueann@midwestlabs.com to establish an account. A sample of about 2 cups is required for powdered milk replacer products. Midwest will provide reduced cost UPS labels upon request for shipping. Once received, testing generally takes about 3-5 days with results provided quickly via email and later by U.S. mail. A variety of ingredient and microbiology testing is available, as listed on their website at www.midwestlabs.com. Contact Midwest for current pricing.

Figure B-1. Esbilac® powder - Calcium and Phosphorus concentrations (%) when reconstituted at 1:2.


Appendix B - Calcium and Phosphorus – Concentrations and Ratio

It is critical to understand the levels of calcium and phosphorus that are being fed to wild animals. Based on the proximate and mineral analysis performed by Midwest Laboratories, it appears that the concentrations of calcium and phosphorus (when Esbilac® is reconstituted 1:2 with water) have declined on average 33% and 48%, respectively, as compared to the prior multi-step dry Esbilac®. However, as shown in Figure B-1, the two minerals remain in acceptable concentrations (as compared to national recommended standards for growth diets under normal conditions for non-lactating rats). Concentration requirements for other species would need to be evaluated.

Additionally, as shown in the chart in Figure B-2, it appears that although the two minerals are present in lower concentrations, their relative ratio is in an acceptable range and appears to have improved over time. The dotted lines in the chart indicate recommended ratios for growth under normal conditions for non-lactating rats (as a benchmark for rodents). The gray shaded area shown ranging from 1.0 to 2.0 represents the normally accepted range for Ca:P ratio for most species.

Figure B-2. Esbilac® powder - Calcium : Phosphorus ratio.




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