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Fox Valley 40/25 - Part 1. Updated lab tests and performance data.

Fox Valley Nutrition manufactures and sells a wide array of milk replacer products for livestock, domestic pets and wildlife in rehabilitation. The 40/25 formulation is a widely used product by many rehabilitators around North America. While the product does not seem to have changed in the past 10 years, a new round of testing has been conducted since this product is used in many wildlife rehabilitator's formula recipes. This article (Part 1) discusses those test results and provides a side-by-side comparison between a 2023 lot and the average of the last 16 lots tested from 2018-2022. Part 2 discusses and offers suggestions on the recent tests, highlighting any major changes (PDF).

FV 40_25 label copy.jpg


In conjunction with WildAgain's recent round of in-depth testing of other powdered milk replacers used by wildlife rehabilitators, Fox Valley 40/25 was also tested, as it is widely used by small mammal rehabilitators in North America. Very little appears to have changed in the product in at least 10 years in terms of ingredients and formulation.

Part 1. This analysis provides the chemical analysis of a 2023 sample of Fox Valley 40/25 and some of its primary formula preparation performance characteristics such as measurement. 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. As a reference point, many of the chemical and physical characteristics are compared to the last 16 lots tested from 2018-2022.

Part 2. An accompanying article discusses some of these test results and offers some suggestions that wildlife rehabilitators may consider when using Fox Valley 40/25.

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

√ Ingredients. No change in the list of ingredients in at least 10 years. Protein is cow milk based, primarily from casein. No pre- or probiotics, or preservatives, are listed.

√ Proximate analysis. There have been changes in protein, fat and carb concentrations, all of which adhere to the Guaranteed Analysis. These changes suggest prior recipes should be reviewed and recalculated for updated nutritional values and to check for acceptable match to the species milk.

√ Ash. As for dietary minerals, very little change. This sample did not contain dietary copper, a key mineral, which has been notably absent in previous test samples. 

√ Fatty Acids. The profile shows a remarkably high concentration of saturated fats (≈70%) and a corresponding low amount of monounsaturated fats. MCT values are lower than found in Fox Valley 32/40 which would be of concern for cottontail rabbit formulas.

√ Rancidity. The 2023 sample tested at non-detected for Peroxide Value,  well below established guidelines for edible oils. Previous PV tests for several Fox Valley products have all tested <5 indicating excellent shelf-stability in terms of very low onset of rancidity in a high-fat content milk powder.


√ Physical characteristics. Powder finely textured, granular, and non-sticky.  Measuring powder by volume or parts rather than weighing continues to cause error rates of + / - 3 to 5% from the calculated average weight of the product. Interestingly, the average weight of the powder, previously very consistent over the last 10+ years, is now 7% lighter than the prior trend. this should prompt review and recalculation of previously used formula recipes. 


√ Reconstitution (wetting and sinking, dispersal and dissolution). The standard WildAgain tests have not yet been performed. Because of the high casein content of the powder, following the complete set of steps in the Mixing Guide is suggested.​

Ingredients (as listed on the package label)


The following table lists the ingredients in Fox Valley 40/25. It seems to have not changed in the last 10 years. As to Primary Ingredients, all fat is provided exclusively from vegetable oil. It is cow milk based for proteins, especially caseins, which is predicted to show poor wetting and sinking during reconstitution. Carbs are provided through the corn syrup solids (glucose), though some lactose is likely supplied through the dried skim milk.

The list of Secondary Ingredients shows many small-quantity additives and supplements for minerals, vitamins, amino acids, and flavorings. 

No fermentation products are included which differentiates Fox Valley from several of the other milk replacers that have begun to add probiotics as well as some prebiotics.

Fox Valley 4025 Ingredients.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. 

The table compares the 2022 sample to an average of the last 16 samples tested (from 2022 back to 2018). There are several notable differences. There is an 8% increase in fat to 25.5% that now adheres to the Guaranteed Analysis. Protein is only slightly lower by 1% by still within the GA. Crude fiber has increased 70% to 1.7%, though the source is unknown from the list of ingredients. These changes collectively cause the total carbohydrates to decrease 10%.  Metabolizable energy content (ME Kcals) has increased slightly, now at 4.67 kcal/gram of powder, likely due to the increase in fat content.


The 2023 values are now included in the Wildlife Formula Calculator. With the changes in the components noted above, it is advisable to review any existing formula recipes based on the latest information.

FoxValley 4025 Proximate Analysis.jpg

Ash - dietary minerals

The following table shows the results of the dietary mineral analysis performed by the lab. The table reflects very little change in concentrations of Calcium and Phosphorus. All other dietary macro minerals showed only slight differences. The micro minerals did show some differences, but in such minute concentrations, these could be partly attributed to standard lab testing measurement tolerances. The one exception is dietary copper which tested as 'non detected' (n.d.) which indicates extremely low or absent, which has been a chronic deficiency in Fox Valley products for years.

Fox Valley 4025 Minerals Analysis.jpg

Fatty acid profile

The fatty acid profile is shown in the following table, which indicates the amount and type of vegetable oil contained in the product. It is notable that the Fox Valley 40/25 has a remarkably high concentration of saturated fat relative to other milk replacers. The total saturated fats represent over 70% of the total fat in the product. The product has a notably lower concentration of the medium-chain triglycerides of caprylic and capric acids as compared to Fox Valley 32/40. This would be of significant concern for formula recipes intended for a species such as the Eastern cottontail that has a dietary need of a higher concentration of medium chain triglycerides (MCT C:8 - C:12).  

Fox Valley 4025 Fatty acid profile.jpg

Peroxide Value (PV) test results

The sample was tested for rancidity, returning a PV (Peroxide Value) of n.d. at 252 days after manufacture. This is well within the max Peroxide Value (PV) of <10 for edible oils. Prior samples of 40/25 and other Fox Valley products have consistently tested <5 for PV. Subsequent testing is also needed to determine if Fox Valley 40/25 continues to demonstrate acceptable shelf stability during the quoted 24-month product life span.

Physical characteristics and measurement error [tests performed by WildAgain]

Fox Valley 40/25 continues to demonstrate the characteristic very fine, granular and non-sticky consistency similar to other Fox Valley powdered milk replacers. This is likely a result of absence of a spray-drying manufacturing process. 

Fox Valley 4025 Texture.jpg

Physical characteristics and measurement error [tests performed by WildAgain]

The very fine texture of the powder continues to minimize measurement error challenges when measuring a given amount of powder to include in a formula recipe. However, mixing by parts using a scoop or other volume measure results in measurement error ranging from +4.8% to -3.2%, a slight improvement from prior samples tested. Weighing the powder eliminates this unnecessary user induced error, provides for a uniform formula at each mixing and preparation using the (Mixing Guide), and helps insure consistent nutrition in the formula.

Also of note is the tendency for the product to have 'gained weight' over the years very slightly, with a notable departure in the 2023 sample, to a lighter weight product by >7%.

FoxValley 4025 Weight Comparison copy.jpg
FoxValley 4025 Weight History copy.jpg

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

WildAgain has not yet performed the suite of reconstitution performance testing on a Fox Valley 40/25 sample. It is predicted that it would perform less well when compared to Fox Valley 32/40 due to the higher protein concentration which is primarily casein. For best results reconstituting this product, the full methodology outlined in the Mixing Guide should be followed.

"What's it all mean?"


See Part 2 for analysis, discussion and impressions of this new round of testing of Fox Valley 40/25.





Fox Valley 40/25 is manufactured and sold as a substitute powered milk replacer product for use with wildlife.

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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