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New Esbilac® (2022) - Part 1. How has it changed?

Long term users of PetAg®'s Esbilac® have seen labels come and go. PetAg®'s Esbilac® has a new label featuring a Black and Tan puppy since early 2022. The label discloses a newly formulated list of ingredients. WildAgain had various lab tests conducted, as well as performed reconstitution tests. This article (Part 1) discusses those test results. Part 2 discusses and offers suggestions on what these changes mean (PDF).

Esbilac Labels History.jpg


It is understood that companies periodically change products to include improvements from new research, manufacturing methods and other factors (e.g., ingredient quality, shelf-life enhancements, etc.). Wildlife rehabilitators purchasing a new Esbilac® (2022) may be hesitant and wary after issues from previous PetAg® changes

Part 1. This analysis provides the chemical analysis of the new formulation and some of its primary formula preparation performance characteristics such as measurement and reconstitution. It does not assess how the new product will perform when fed to orphaned wildlife in rehabilitation, though some of the information certainly can be used with decisions and use. 

Part 2. An accompanying article (PDF) discusses some of these more significant changes and offers some suggestions that wildlife rehabilitators may consider when deciding what these product changes mean and how they may affect feeding young wild mammals.

The following list highlights some of the key findings prior to a more detailed presentation of test results and analysis. 

√ Ingredients. Many listed ingredients are the same, though likely in different concentrations or amounts. Dried corn syrup has been newly added, as has guar gum and powdered cellulose (fiber).

√ Proximate analysis. Protein has decreased 10% (within tolerance of Guaranteed Analysis-GA); has double the GA of crude fiber; and a 33% increase in calculated carbohydrates (NFE).

√ Ash. Chronically light on dietary minerals, the new formulation shows a further 7% decrease overall, as well as individual decreases in all mineral concentrations except for zinc. Calcium is barely above the generally accepted 1% concentration threshold.

√ Fatty Acids. The profile shows a 60% increase in polyunsaturated fats (a 57% increase in Linoleic acid (C18:1 Cis) alone), and a 25% decrease in overall saturated fats.

√ Rancidity. Esbilac® continues to demonstrate acceptable shelf-stability with the 2022 sample testing at a PV=2.4 at 7.5 months since manufacture, well within established guidelines for edible oils. Proper storage is still critical.


√ Physical characteristics. Powder is still loose, fluffy and sticky. Measuring powder by volume or parts rather than weighing continues to cause error rates of + / - 8 to 10% from the calculated average weight. The average weight of the powder is trending slightly heavier over the last six years (≈ +3% per year on average).


√ Reconstitution (wetting and sinking). Very good performance when correctly adding powder to warm water, with test samples fully submerged in <1 minute. 

√ Reconstitution (dispersal and dissolution). An 8-hour resting period from preparation (mixing) to final use (feeding) improves final reconstitution by 88%. Without the rest period and quickly prepared for an instant use/feeding, over 16% of powder remains dry and not fully reconstituted.

Ingredients (as listed on the package label)


The following table lists a side-by-side comparison of the ingredients of the pre-2022 and the new 2022 formulations. The notable 2022 change in the Primary Ingredients listing is the addition of dried corn syrup. All other ingredients are listed in the same order of prominence though concentrations or amounts may have changed. 

The list of Secondary Ingredients shows many small-quantity additives and supplements have changed in their presence/absence and likely concentrations. Guar gum and powdered cellulose are new ingredients presumably intended for prebiotic benefits that are essential for digestion, development, and the immune system. 

The fermentation products presumably intended for probiotic benefits have not changed. They are listed in the same order of prominence, though again, actual concentrations may have changed in the new formulation. 

Esbilac Ingredient Comparison.jpg

Proximate analysis

The following table shows the results of the proximate analysis performed by the lab as compared to the Guaranteed Analysis (max/mins). The red shaded values indicate where the lab analysis determined that the component concentrations failed to adhere to the maximum or minimum guarantees. Most of those outside guaranteed limits are minor and within lab testing tolerances, except for crude fiber which is almost twice the guarantee. 

Moisture still exceeds the maximum guarantee of 5%, though has improved, down 9% overall from the pre-2022 sample. This results in a higher percent of overall total solids in the new formulation. Also notable is the 3.5 percentage point drop in protein concentration, accounting for most of the 3.9 percentage point increase in carbohydrates. Due to the slightly higher fat content of the new formulation, the metabolizable energy content (ME Kcals) equals 5.64 per gram of dry powder. That is a slight 1.6% increase over the 2021 sample of 5.55 Kcals/gr. These changes in the proximate values may require adjustments to previously used formula recipes, which can be easily calculated with the Wildlife Formula Calculator

Esbilac Guaranteed Anaylsis to Actual.jpg

Ash (dietary minerals)

The following table shows the results of the dietary mineral analysis performed by the lab. Over the last 15 years, PetAg® powdered milk replacers have tested lower in overall ash than Fox Valley Nutrition milk replacers, averaging 25% less in Calcium and 15% less in Phosphorus. This trend continues with the new Esbilac® formulation, down 7% from the pre-2022 sample in overall ash level. Calcium tested at 1.04% (just above the generally accepted minimum concentration of 1% for milk) and 0.67% for Phosphorus. [This is another example where, in this case, the Ca:P ratio of 1.55 can be misleading. While a ratio of 1.55 is very acceptable in milk, in this case it is calculated from Calcium and Phosphorus concentrations that are remarkably low. It is always advisable to look at the individual mineral concentrations as well as the ratio.] As for the other minerals, all concentrations tested at 10-50% lower concentrations, except for Zinc.

Dietary Minerals Table.jpg

Fatty acid profile

The fatty acid profile of the new formulation is shown in the following table. It shows an 8-percentage point drop in total saturated fat when compared to the pre-2022 formulation, with a corresponding 9 percentage point increase in polyunsaturated fats. This is likely a change in the mix of vegetable oils being used, with a 60% increase in linoleic fatty acid, which could suggest an increased mix of sunflower, safflower, soybean, corn, and/or canola oil - which are all primary sources of linoleic acid. [The decrease in total saturated fats would be problematic for species that have dietary needs of a higher concentration of medium chain triglycerides (MCT C:8 - C:12) such as Eastern cottontails and may require very minute MCT supplementation to formula recipes.]

Esbilac Fatty Acid Profile.jpg

Peroxide Value (PV) test results

The 2022 Esbilac® sample was only 7.5 months post manufacturing when tested for rancidity, with a test result of 2.4. This result is well within the max Peroxide Value(PV) of 10. Four pre-2022 samples had been previously tested (2017-2019) with a mean test PV of 6.6 (ranging from 2.5 to 12.4). Esbilac® has generally shown test results of greater shelf stability (lower PVs) than the other PetAg® products of GME® and KMR®. Subsequent testing is needed to determine if the new formulation continues to demonstrate acceptable shelf stability during the quoted 24-month product life span.  

Esbilac PV tests.jpg

Physical characteristics and measurement error [tests performed by WildAgain]

The new Esbilac® formulation continues to have the characteristic very loose, fluffy and sticky consistency as in prior formulations, and similar to other PetAg® powdered milk replacers. This is likely a result of the spray-drying manufacturing process. This physical property continues to provide challenges when measuring a given amount of powder to include in a formula recipe. Mixing by parts using the provided scoop or some other volume measure results in measurement error ranging from +9.5% to -8.1. This is an approximately 10% increase in the error range from a 2021 lot manufactured just 6 months prior. Weighing the powder eliminates this unnecessary user induced error, provides for a uniform formula at each mixing and preparation (Mixing Guide), and helps insure consistent nutrition in the formula.

Another benefit of weighing (versus volume scooping) is the notable trend of Esbilac® 'gaining weight' over the past several years. Averaging 6.2 grams per tablespoon in 2016, the 2022 sample now averages a weight of 7.4 grams, a 20% gain in the weight of the powder. 

Esbilac weights 22 v 21.jpg
Esbilac weight history.jpg

Reconstitution tests - wetting and sinking [tests performed by WildAgain]

The 2022 Esbilac® sample demonstrated very good wetting and sinking of the dry powder, being completely submerged in the warm water within 1 minute (shown in the first image below that is a side by side of normal lighting (left) and a copy with enhanced contrast (right) to show the submerged but undispersed powder). This is a significant improvement over the pre-2022 formulation (shown in the two samples in the second image), where those samples had significant amounts of unwetted powder yet to break the surface tension of the water after a full 5 minutes. However, even with the improved performance of the 2022 sample, much of the wetted powder had not fully dispersed in the water after 5 minutes. This demonstrates that mechanical mixing would be required to achieve more complete reconstitution.

Esbilac 2022 Wetting and Sinking.jpg
Esbilac Pre 2022 Wetting IMG_2260 copy.jpg

Reconstitution tests - dispersal [tests performed by WildAgain]

The formula was whisked by hand for 5 minutes (or longer) until all visible dry powder had been determined to be dispersed so no small clumps were visually present – and it appeared smooth, ‘milky’ – and presumed ‘ready to feed.’ The formula was then poured through the stack of sieves, with the largest mesh size on top (500µm). The image that follows shows the unwetted powder retained (trapped) by the 500µm sieve, even though visually it had appeared that the formula just prepared had been completely mixed and free of any dry powder clumps. The image on the left is the formula that was mixed and not allowed to rest, simulating an instant mix use/feed as directed on the product label instructions. The image on the right shows significant improvement (in terms of less unwanted, dry powder) after allowing the formula to simply rest a full 8 hours

Esbilac 2022 reconstitution 500um sieve.jpg

The instant mix (no rest sample) showed a surprising and disturbing outcome in the smaller mesh sieve. After removing the 500µm and 250µm sieves from the stack, the 125µm sieve was found to have retained enough unwetted, dry powder to actually obstruct flow of liquid through the sieve (left image below). A plastic scraper was then used to see if some of the liquid and powder could be forced to pass through the smallest mesh sieve. The image on the right shows that almost all the liquid could be forced through, but the undispersed powder remained in the form a thick wet sludge. Most would agree that this level of sludge would be difficult if not impossible for young, developing GI tracts to digest, absorb and utilize, and likely result in severe intestinal distress in very small, young wild mammals. The sample allowed to rest for 8 hours (not shown below) showed very minimal liquid flow obstruction and no noticeable wet sludge – and could be generally expected to be easier for young wild mammals to digest.

Esbilac 2022 reconstitution 125um sieve.jpg

Reconstitution tests - Observed results

Instant mix - no resting time. When compared to the 2021 formulation, the new Esbilac® shows a doubling in the amount of dry, unreconstituted powder retained/trapped in the stack of sieves when prepared for use as an instant mix. This represents significantly less complete dispersal and dissolution (reconstitution) of the powder. The chart below shows the sieves retained (trapped) over 16% of the dry powder after the sieves were drained and dried of all remaining moisture. Most of the dry powder material was retained in the 125µm sieve. (For reference, complete dissolution would achieve the normal range of milk particle size 10 to 100 times smaller and would easily pass through the last sieve.)

Resting time of 8 hours. When the prepared formula sample was allowed to rest for 8 hours, an 88% improvement in dissolution resulted, with very little dry material remaining. This is also a significant 25% improvement over the pre-2022 Esbilac® 8-hour rest sample. 

While the improvement in dispersal is encouraging, it should be noted that the dispersal efficiency of Esbilac® comes in at last place when compared to all other commonly used powdered milk replacers, even when given the time to rest for 8 hours. This is apparent in the second chart below. This suggests that the added resting time is a critical step to achieve a suitable liquid formula for feeding for Esbilac®, and any powdered milk replacer – and the health of young wild mammals to which it is fed.

Following the immediate two charts below is a visual presentation of how the two formulations of Esbilac® performed in the sieves. They are presented in order of the largest mesh sieve to the smallest.

Esbilac Reconstitution eff chart.jpg
All Powders Dispersal Compared.jpg
Esbilac 2022 500 sieve.jpg
Esbilac 500 composite.jpg
Esbilac 2022 250 sieve.jpg
Esbilac 250 composite.jpg
Esbilac 2022 125 sieve.jpg
Esbilac 125 composite.jpg


Esbilac® is manufactured and sold as a food supplement for dogs, and not intended to be a sole source food for developing puppies. Wildlife rehabilitation is considered an off-label use.

Product assays performed by the independent lab adhere to the Official Methods of Analysis of AOAC INTERNATIONAL (Association of Official Analytical Chemists) and the Official Methods and Recommended Practices of the AOCS (American Oil Chemists Society).

The authors have no conflicts of interest with the independent lab, or any of the products or manufacturers discussed in this article.

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