Wombaroo Rabbit Milk Replacer - Part 1. Product testing. 

Summary

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A critical challenge facing mammal wildlife rehabilitators is providing a suitable substitute milk replacer to feed orphaned, nursing wildlife. The task involves understanding the composition of the mother's milk; then using one or more commercially available milk replacers (generally in powdered form) to construct a recipe that matches the mother's milk; and then preparing the formula to achieve a properly reconstituted formula. While rehabilitators have been generally limited to milk replacers commercially available for domestic animals (companion and livestock), other products have been brought to market in recent years that are formulated for other species - and may provide a closer match to certain wildlife species milk or used to blend a composition that is a closer match to a species. Wombaroo is a company that has a line of products that targets the market beyond puppies, kittens and livestock. Assuming that Wombaroo's Rabbit Milk Replacer is actually formulated for various domestic species of rabbits (European, California, NZ-White, etc.), its applicability for wild lagomorph species found in North America is worth considering.

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Part 1. This analysis provides the chemical analysis of Wombaroo Rabbit Milk Replacer 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. 

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Part 2. An accompanying article discusses some of these test results and offers some suggestions that wildlife rehabilitators may consider when evaluating the product for use with wild rabbit species. 

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

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√ Ingredients. A primary differentiating characteristic of the product versus most of the other commercially available milk replacers is the use of human grade ingredients as was indicated in direct discussions with Wombarro. Proteins are sourced from a recombination of cow's milk fractions. Most of the fats originate from vegetable oil as well as some fish oil for the Omega-3 and Omega-6 fatty acids. The label also references "milk oil" fatty acids. The absence of added fermentation products or prebiotics is noted, as these supplements are becoming more routine with other US manufactured milk replacers (such as with PetAg®).

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√ Proximate analysis. The product adheres to the Typical Analysis (TA) concentrations provided on the label as a 37% protein and 42% fat formulation, but does exceed the TA moisture content. Overall ash is about 15% below the TA value of 6%.

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√ Ash. As for dietary minerals, calcium and phosphorus tested at .99% and .83% respectively. These concentrations are slightly lower than most cow's-milk based PetAg® products and noticeably lower than Fox Valley Nutrition products. However, the overall ash content at 5.12% seems very acceptable.  

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√ Fatty Acids. The relatively high concentrations of Caprylic (C:8) and Capric (C:10) acids are not surprising given the nutritional needs of young rabbits for these specific saturated fats. The product has one of the highest percentages of saturated fats of any of the other milk replacer tested by WidAgain. The corresponding and relatively low concentration of unsaturated fats should enhance shelf-stability.

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√ Rancidity. Though not indicated on the labeling, other websites suggest that certain Wombaroo powder products have a shelf life of 18 months (if unopened and stored properly). Assuming an 18-month life, the sample tested was from a newly purchased, unopened container and was ≈450 days post-manufacturing (≈ around 80% in to its shelf life). The peroxide value tested at 2.3 which is well within established guidelines for edible oils of <10. Although just a single sample, this does suggest that the product has very good shelf-stability.

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√ Physical characteristics. Powder is loose, fluffy and sticky. Measuring powder by volume or parts rather than weighing produced error rates of +6 to -12% from the calculated average 8.4 gram/Tbsp weight of the product. 

 

√ Reconstitution (wetting and sinking). When correctly adding powder to warm water, the product showed very good wetting performance, with the test sample 90% wetted in <5 minutes. However, sinking performance was relatively poor with much of the wetted product still floating and unable to break the surface tension of the water to fully sink to the bottom of the mixing container.   

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√ Reconstitution (dispersal and dissolution). Hand stirring/whisking for 5 minutes was required to completely submerge the wetted powder and produce a smooth, milky liquid that appeared free of any remaining dry powder. The reconstitution tests showed that when prepared for an immediate use, 3.5% of the powder remained trapped by the three sieves. While this is relatively good performance when compared to other milk replacers, an 8-hour resting period from preparation (mixing) to final use (feeding) improved final reconstitution by 75% with only less than 1% of the powder not fully reconstituted. This is outstanding performance compared to the other milk replacer products, especially those that are cow-milk based.