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Milk Replacer Project 2021:

Some FAQs as Wild Mammal Baby Season Approaches


Many rehabilitators continue to discuss commercially available milk replacers used for wild mammal babies, especially due to the concerns of health problems in the animals fed formulas in 2019. They ask, “What’s happening with milk formulas?”, “What should I order?”, “What recipe should I use?”, and “How can I ensure I am feeding suitable formula to the wild mammal orphans and avoid causing problems?” 


Those are great, straightforward questions. The answers, however, are not short or easy. As much as we appreciate that rehabilitators want direct, decisive and simple answers, there are many considerations involved in formula decisions. Knowing that, listed below are some frequently asked questions (FAQs) posed to WildAgain during our continuing research – followed below with some responses drawn from our research and interviews and surveys with over 130 rehabilitators. More thorough information on product testing, formula preparation methods, factors that may have caused previous concerns, and possible ways to prevent them – as well as continuing research - will be updated as available.



1. What caused the nutritional problems in wild mammal babies in 2019?  


2. I need milk powder. What powdered milk replacer should I order?


3. How can I know I’m using the ‘right’ powdered milk replacer product(s) and recipe for a substitute milk formula?


4. How can I learn more about the mother’s milk of the mammals I rehab?


5. Back to powdered milk replacer products: how do I select the right one?


6. Is it okay to blend multiple powders together? What about adding other ingredients? See the new mixing guide. 


7. Some species appear to need more fats in the formula than the milk replacer powders provide, such as squirrels and cottontails. So which fats are effective options?


8. How can I create and evaluate formula recipes for the mammal babies?  


9. Now, can I finally just mix the formula ingredients and feed?


10. Many rehabilitators have made formula using powder, water, etc. by measuring ‘parts’ of each ingredient for years and it worked. Why would we now consider weighing instead?


11. After reported problems, PetAg® wrote they were going to change Esbilac® in fall, 2019. Did they change it? Is it now effective and safe?  


12. What about using Goat’s Milk Esbilac® (GME®)?


13. What did rehabilitators feed wild mammals in 2020 and with what results? What about in 2021?



How do I evaluate the results of my formula decisions?


14. What is ‘good health’ in animals? 


15. How do I know if I’m seeing appropriate growth and development rates?


16. How can I recognize early signs of nutritional problems?


17. How do I know how much and how often to feed the wild babies to make sure they are getting enough daily calories?  


18. Wrap-up



1. What caused the nutritional problems in wild mammal babies in 2019?  


Data collection and analysis in 2019-21 strongly suggests multiple factors contributed to concerns in recent years. First, while health problems developed in some wild mammal babies in 2019 that appeared to be directly related to nutrition, others did not develop similar problems. Second, there are many possible contributing factors to consider when diagnosing these problems – including species, age of animals, health conditions, recipes and mixing methods, feeding practices, and, yes, milk powders! Rehabilitators and others are continue working on and investigating these situations, and the research continues. Meanwhile, WildAgain does not believe it is appropriate to suggest there is a single cause or solution, nor will we recommend a specific product or formula recipe. More here (PDF). 


2. I need milk powder. What powdered milk replacer should I order?


First, choose milk powders that experienced and trusted rehabilitators have reported having no or only minor problems with in 2019 - 2021. When ordering your milk powders, consider placing a small initial order rather than making large purchases. Published research reveals substantial benefits from fresher milk powders in improved reconstitution and less chance of rancidity. Second, considering there are benefits from recipes using blending milk powders, a growing number of rehabilitators are purchasing products from two different manufacturers.  


3. How can I know I’m using the ‘right’ powdered milk replacer product(s) and recipe for a substitute milk formula?


Rehabilitators understand the best milk for young mammals is the milk from their mothers. Clearly, there are no commercial sources of milk from mother squirrels, opossums, rabbits, raccoons, and other wild mammals (nope, no dairy farms milking those species, regardless of the label placed on a milk replacer container). When wild mammal babies are brought into rehabilitation, the next best thing is to try to provide a substitute milk formula that closely matches the milk composition for the species. As a result, rehabilitators use commercially available milk replacer products to try to create a formula that meets the species needs and results in an acceptable level of growth, health and development. However, we are mindful that manufactured milk replacers (generally designed for domestics or livestock) are not going to meet the precise composition, nutrition, quality, purity, and digestibility as the mother’s milk.


As to feeding the ‘right product?’ There are several parts to that question:


(1) Is the milk powder one that can be used in a way to match the milk composition of the mother? Historically, people buying milk powders have used the Guaranteed Analysis (GA) on the label to make that decision with a focus on percentage content of solids, proteins and fats. [NOTE: Tests by an independent lab have revealed variations in some of the products that are different from the GA on the labels. A number of the products have been chronically below the GA values for fat content over the last several years.]


(2) Have rehabilitators reported ‘good health, growth and development’ with animals when one or more specific milk powders have been a major ingredient? Or have recent problems been reported? 


(3) What is the product history (e.g., quality, effectiveness, reliability, manufacturer transparency, and lack of problems)? In addition to being able to learn about those things from consumers and rehabilitators, recent research provides some information on this.


As to the ‘right recipe’, that goes back to looking at the milk composition studies for the species and developing a recipe that is a proportional match to mom’s milk, as discussed in WildAgain's Wildlife Formula Calculator. But other important factors to consider include: how the formula is prepared, feeding amounts/frequency, digestibility, as well as its effectiveness with the animal. 


4. How can I learn more about mother’s milk of the mammals I rehab?


Information on cow, goat, sheep and yak milk composition is extensive worldwide. Published research on wildlife species milk composition analyses is more limited, but can be found in publications on scientific research studies ( offers resources). Published milk composition analyses for common mammal species rehabilitated in North American also are available in the downloadable Wildlife Formula Calculator, and other milk composition species and studies can be added, including by the user.    


5. Back to powdered milk replacer products: how do I select the right one?


There is no easy answer on this question either. By necessity, many mammal rehabilitators use manufactured milk powders as the primary ingredient of the formula they feed the young mammals. Some of the manufacturers use a product name (e.g., Esbilac® or KMR®), while others refer to the product by the species it might be used to feed: opossum, squirrel, raccoon, or deer formula. 


Milk replacer product labels include information on guaranteed minimum percentage of protein and fat content (generally listed in that order), such as Fox Valley 32/40 (32% protein, 40% fat). Referring to any milk powder by its primary components (solids/proteins/fats) allows for easier consideration of how they may be used as parts or ingredients to create a recipe/formula that more closely meets the milk composition analysis for the species. 


Rehabilitators know that young mammals need both proteins (essential for bone and tissue development and growth) and fats (necessary for growth and energy consumed for physical activity) – as well as other key nutrients, such as the primary dietary minerals (calcium, phosphorus, manganese, copper and iron). While those considerations can be used when selecting products, rehabilitators should also consider the other factors mentioned – like comparison to the mother’s milk; the animal’s health, growth, and development; product quality, freshness and digestibility; and more. There are also considerations of availability, cost, budget, etc. The person selecting the milk replacer products, recipes, and so forth will be considering a wide variety of factors. Research, announcements and other sources may reveal changes on composition, quality, results that affect decisions.


6. Is it okay to blend multiple powders together? What about adding other ingredients?


Rehabilitators and others reviewing the milk powder compositions have noted that only mixing a single milk replacer powder with water results in formulas that are very often unlikely to be a close match for the milk composition for wild species. Whereas, combining milk powder products with different nutritional compositions, and possibly combining other ingredients, may achieve a closer match for the milk composition for the species. [Note: if using multiple milk powders, it is critical to reconstitute each powder separately to a liquid form, and then combine the liquids into a finished formula. See the new mixing guide.]  For example, some rehabilitators add small amounts of extra fat to the recipe for a species needing more fat that can be provided solely from milk powders. For species needing higher protein levels in their milk, they select a milk replacer higher in protein, blend milk replacers to achieve that level, or may add another protein source. Others might adjust the ingredients or concentration for different stages of lactation. That said, it is essential to understand the reasons, possible affects, potential benefits and problems from combining different milk powders and other ingredients - or changing ingredient amounts (including water). Such changes must be made deliberately and cautiously, and the results closely monitored since they can have significant impacts on the health and survival of the animal being fed that formula.   


Some rehabilitators believe that poor development in an animal is due to a mineral deficiency in the formula, and have considered adding a mineral supplement. One needs to know exactly what minerals the animal needs based on species and age. Unfortunately, such data is extremely sparse for most species. Other variables include: the interaction with other minerals and components; amounts of minerals in the rest of the food (from current lab tests, not just on labels); the digestibility of the minerals; potential problems and much more – and those are difficult to know. Adjusting mineral levels is extremely complicated; microdoses are very hard to measure.  Errors can result in serious and unintended consequences. Mixing ingredients or recipes that look like milk and that a mammal baby will eat does notguarantee that it is nutritious, healthy or can be utilized by a not yet fully developed digestive tract. If a hungry young mammal is only offered formula, it may eat it regardless of whether it is appropriate, effective or even safe.


Another key consideration is how, when, and with what methods the different formula components are combined. The type, blend and amount of ingredients, as well as different preparation methods, are major considerations – and again require much further attention. 


7. Some species appear to need more fats in the formula than the milk replacer powders provide, such as squirrels and cottontails. So which fats are effective options?


Like many of the other questions in this list of FAQs, the answer is complicated and requires considerable information. There is some basic information on the role of fats in milk replacer powders here, as well as trend information based on recent lab tests of the milk replacer powders. Again, formula decisions are always the responsibility of the individual rehabilitator. At times, supplemental fats need to added to the formula recipe to better match mother's milk. Some common alternatives are discussed here and here.



8. How can I create and evaluate formula recipes for the mammal babies? 


As mentioned, scientific publications provide complex equations that will yield percentage compositions (solids/fats/proteins/carbs/kcals) for any combination of ingredients in a formula recipe. Some rehabilitators choose to simplify and accelerate the recipe creation process by using the WildAgain Wildlife Formula Calculator, which is prepared for rehabilitator use. This calculator includes the current and longitudinal nutritional profiles of milk powders from several manufacturers, various products, and tests on multiple lot numbers conducted by an independent laboratory, as well as other tests. Using current information from the independent lab tests can prove to be very insightful, since the product labels may be out-of-date or even inaccurate at times. 


It only takes a few easy steps to use the Wildlife Formula Calculator. Step 1 starts with selecting the species of “mom’s milk” that the person wants to match. These values are based on nutritional analyses from various studies done on the milk of each species. In Step 2, the person selects the ingredients included in the recipe (this includes milk replacers as well as other additions, e.g., heavy whipping cream). Then in Step 3, the amounts are indicated by the user, either by parts – like one part powder, 2 parts water- or by weight of each ingredient. Finally, the results will then show how closely that “recipe” matches mom’s milk - including solids, protein, fat, carbs, kcals, calcium, phosphorus, and even the Ca:P ratio. While the calculator can do the math, a perfect 100% match to mom’s milk is highly unlikely OR recommended (see explanation in calculator). Follow these links for a more thorough discussion on matching mother's milk and more tips on using the calculator.


Comparing formula recipes to the mother’s milk composition for the species allows the rehabilitator to try to more closely match the mother’s milk. That said, even if a ‘recipe’ looks like a reasonable match to mother’s milk by the numbers, it is still essential to assess how well the formula actually works when fed (digestibility, growth rate, etc.) and adjust as needed. On the flip side, if products and recipes do not reasonably match the nutritional profile needs of the species, that may result in problems either immediately (e.g., gastrointestinal disorders, hunger, slow weight gain) or later (e.g., malnutrition, malformations, fractures). It cannot be overstated that this is difficult and definitely benefits from considerable study – and, hopefully, supplemented by consultation with other experienced rehabilitators prior to and during decision-making.


9. Now, can I finally just mix the formula ingredients and feed?


Once the products and recipes are selected, many assume the formula is ready to mix and feed. Earlier research from 2010 conducted by WildAgain, and expanded in 2020, shows that there is far more to preparing the milk powders than just combining milk powders with water, mixing and feeding immediately. 


Over the years, many rehabilitators have followed instructions on the milk powder labels saying to scoop a ‘part’ of powder and mix with two ‘parts’ water. However, extensive tests involving weighing milk replacer powders shows substantial variability in the scooped weights of different lots of the same products – as well as weight changes documented over 15 years. This means that there can be significant variation in the amount of powder actually being used (too much/too little) which can adversely affect the concentration of the formulas – which then affect nutrition, growth and development. Further, such variations can cause under- or over-feeding, gastrointestinal disorders, hunger, and more. 


While it is fairly easy to weigh the ingredients, one must remember that, for a 2:1 water:powder mix, one does NOT just weigh the milk powder and double that amount to get the weight for the water. Water weighs about 15 grams per tablespoon, whereas the milk replacer powders range in weight from about 5.5 to 7.5 grams per tablespoon. So, if you weigh 30 grams of milk powder, you cannot use double that weight in water. If you want to confirm the weights planned for a formula recipe, the nutrition calculator offers a new (2020) feature that converts the individual recipe ingredient values (measured in parts) to corresponding weights (measured in grams). Changing from the scooping measurement method to weighing takes some adjustment, but it is far more accurate.


Some milk powder directions say to mix with warm water around 100°F (for reference, a hot shower is around 105°F). Other products do not specify a water temperature. Dairy researchers and others have studied how differently produced milk powders respond to different water temperatures, mixing methods and ‘resting times’.


However, ongoing and expanded research is investigating how milk replacer powders rehydrate and reconstitute at different temperatures and ‘resting’ times. So far, the results are somewhat mixed when compared to 2010, which could be a result of a change in both the manufacturing process or product formulation over the last 10 years by one or more of the manufacturers. The manufacturers offer little transparency into those metrics. Those tests and analysis are beginning to show preliminary results summarized here.



[Note: Early research of dog milk composition reported about 34% protein and 40% fat. Manufacturers produced milk replacers for that relevant protein/fat level, and other nutrients considered for growth and health. Milk replacer powders, such as Esbilac®, have been manufactured to be made into formula and fed to puppies since the 1960’s. Currently manufactured by PetAg®, Esbilac® continues to be produced and marketed as a supplemental food for puppies, not a sole diet. In 2014, a veterinary nutrition team conducted research on dog milk composition and conducted extensive studies comparing puppy milk replacers. That paper clearly explained the milk powders produced for puppies still have a long way to go to meet nutritional needs of the animals. Plus, the study explained that the product labels also need improvements. The paper is at ]


10. Many rehabilitators have made formula by using ‘parts’ of powder, water, etc. for years and it worked. Why would we consider weighing instead now?


As discussed in an earlier FAQ above, weighing ingredients provides for a more accurate and consistent formula being fed at each feeding time interval. Some people may feel this getting too exacting about making formulas, especially when the caregiver’s time is likely already stretched thin. Perhaps true, but with all of the other variability in the formula (product variability between lots; variability in reconstitution; variability in measuring dry powder by scooping, etc.), weighing can totally remove one of these variables with just a small amount addition of time and effort. A more thorough discussion of this can be found here and here.


11. After product problems were reported in mid-2019, PetAg® wrote they were going to change Esbilac® in fall, 2019. Did they change it? Is it now effective and safe?  


In September 2019, PetAg® sent an email ‘alert’ and a follow up set of FAQ’s to rehabilitators who had contacted them with concerns about Esbilac®. They explained that the health problems rehabilitators had been reporting were likely related to the particle size of Dicalcium phosphate (DCP) in Esbilac®, which had been changed by the supplier approximately two years prior. They indicated that the larger particle size of the DCP would be difficult to be broken down (digested) and absorbed by small wildlife, even though it was still ‘satisfactory’ for use with puppies. In a follow up statement, they verified that they were able to secure a source for more finely milled, micronized DCP and that the modified Esbilac® powdered product would be available in 30-60 days. It was later learned specifically that Esbilac® manufactured after September 30, 2019 would be produced with the new micronized DCP. 


WildAgain obtained the Esbilac® manufactured in October 2019. That sample was tested at the lab and the results (lot # 2889E-2969 #03) are posted in the Esbilac® tab on the Lab Test Data Spreadsheet, as well as other tests from Esbilac® produced in 2020. While the test results show how the milk powders change in terms of primary components (percentage content of protein, fat, primary minerals and trace elements), the tests do not measure content (or particle size) of specific supplemental ingredients such as DCP, or comment about digestibility, effectiveness, or safety. For this reason, while one would hope PetAg® changed the DCP to be more digestible and effective, the lab testing is unable to confirm whether the DCP has been changed to a form that is more readily absorbed by the wild mammal young. To date, reports from rehabilitators using Esbilac® produced from October 2019 and in 2020 have not mentioned nutritional problems to WildAgain.


PetAg’s website announced that they recently constructed and opened new facilities in Illinois, Arkansas, and Missouri. While PetAg certainly expects their expanded and enhanced facilities will help their operations and products, the outcomes from those facilities are not fully known to the consumers.



As mentioned, WildAgain continues to conduct research on the milk replacer powders. The independent lab tests on nutrient profiles, and information from other WildAgain tests (e.g., weights, rehydration), are being posted on in the Wildlife Formula calculator, spreadsheets, measurement paper, etc. Those tests do not assess the digestibility, safety or ultimate effectiveness of any of the milk powders. 


Thus, WildAgain cannot assess these aspects of the products, since manufacturers may change the products (formulations, ingredients, suppliers, manufacturing methods, facilities, staff, ownership, etc.) at any time and without notice. Plus, factors like recipes, product preparation, and so forth may affect the results from using the powders. Rather, WildAgain will provide information when available to support rehabilitators as they consider such decisions – including the information in the responses to these FAQ’s. 


12. What about using Goat’s Milk Esbilac® (GME®)?


WildAgain continues to recommend rehabilitators consider many factors when selecting products: nutritional composition of the milk replacer powder, test results, results reported by other experienced rehabilitators, etc., and then make their own decisions. 


The GME label guarantees a minimum concentration of 33% protein and 40% fat (dry matter basis). In September 2019, PetAg® suggested GME® as a substitute for Esbilac®, even though they manufacture and market another product line, Zoologic®, that has a similar 33/40 formulation. However, independent lab tests reveal some substantial variations from the nutrition profile on the GME® label.


Some products that contain goats’ milk have a slightly different odor than those products that include bovine milk, including GME®. The odors are just simply different. However, since some GME® had a substantially stronger odor, which seemed to be more of an ‘off-odor’, additional lab tests were conducted. It is well known that any food products with high levels of fat, which certainly include most milk replacement powders, can be become rancid if exposed to heat during packing, storage, transportation, etc. They can also become rancid if not stored properly once the package is opened. They can develop rancidity but excessive storage time. Lab tests revealed six out of six GME® cans (two directly obtained from PetAg and four purchased from retailers) had elevated peroxide values (PV) that showed moderate to high rancidity levels. This suggests becoming familiar with the milk powders appearance, normal and fresh odor, etc. is absolutely essential for rehabilitators. These PV test results do not suggest a problem with all GME®, but do suggest those using it pay close attention to any off odors, appearance and reluctance of animals to eat it. Also, these test results serve as a reminder to store any milk powders in a cool environment and to always check the odor of the milk powders whenever opening and before using. Follow this link for more info on rancidityways to check for itcurrent test results and storage information.


13. What did rehabilitators feed wild mammals in 2020 and with what results? What about in 2021?


As before, rehabilitators continue to make their own decisions about products and formula recipes – and many options are currently being used. WildAgain does not and cannot know all the options. However, there have been thoroughly documented reports in 2020 from squirrel, opossum and cottontail rehabilitators seeing expected growth and development, and good health when fed formula made with one or more of the following approaches: 


1) formulas were prepared using milk powders from two separate manufacturers (blended formulas) to help balance nutrition, minerals, etc.,


2) attempts were made to more closely match the milk composition analysis of the species using recipes analyzed using information from the Wildlife Nutrition Calculator, 


3) milk powders were prepared following modified and enhanced rehydration and reconstitution methods (especially for blended-product recipes), and


4) in many cases the ingredients of a recipe were weighed (not scooped volumes) to ensure a more accurate formula mix of the intended milk formula nutritional composition.


More results will be reported as additional documented case information is available on species, ages of animals, etc. This will include cases and discussions of some of the approaches that proved more successful. 





14. What is ‘good health’ in animals? 


Identifying the causes of health problems in young mammals while on formula in 2019 was especially challenging, due in part to variable definitions of what rehabilitators considered ‘normal’ and healthy. In some cases, the reported health problems could have been a result of multiple contributing factors (rehab practices, specific products or recipes, mixing and reconstitution methods, etc.). The real answer to this question depends on what a rehabilitator means when using the word ‘healthy.’  


Measures and definitions of ‘normal’ and ‘good health’ vary by person, rehab facility, veterinarian and experience. Is it the observed weight gain, healthy stool, or fur quality?  Is based on behavior?  And if so, should it be compared to typical of the species when raised by their mothers in the wild - or is it different when the young are raised in a rehabilitation setting? What are or should be the benchmarks? It may be beneficial for rehabilitators to establish a more mutually understood definition of ‘healthy’ for referring to conditions or causes of “unhealthy”, including nutritional factors.


15. How do I know if I’m seeing appropriate growth and development rates?


Rehabilitators know that diet directly influences growth and development. Familiarity with the natural history of the species, knowing how the young animals appear when they first arrive at rehab after feeding by their mothers’, and normal weight ranges are all vitally important information used to determine the health of an animal. 


Rehabilitators regularly monitor weight gain to determine if the animal is growing and whether they are within a normal range. If the animal is not gaining weight at the expected rate (e.g., slow, too fast, or inconsistent), various factors should be assessed and considered. While an animal’s rate of weight gain may be a little ‘slow’ on some diets or they seem very hungry, some consider that acceptable as long as the animal does not show other health problems, such as diarrhea. Others try to identify reasons for slow weight gain (e.g., formula products, recipes, feeding amounts and frequency, endoparasites) and adjust. On the other hand, if the animal is gaining more weight than normal and looking substantially ‘heavier/rounder’ than when fed by its mother, reasons for that are considered as well (e.g., such as excess fat or kcals in the diet or overfeeding). 


Development is more than just weight gain. It involves physical and behavioral changes, such as coat/fur development, the opening of eyes and ears, ability to thermoregulate, adept mobility, alertness, and even play. They also consider activity level, strength/muscle tone, body mass, and speed.  Monitoring development means noting how the animals compare to the young animals raised by their mothers.


16. How can I recognize early signs of nutritional problems? 


Again, this is a very complex topic – and it builds on the topics of health, growth, and development. It means considering what is ‘normal’ and ‘healthy’ for the specific species, age, and developmental stage - and constantly monitoring those details. It involves noting factors like weight gain, gastrointestinal health (e.g., bloat, diarrhea, constipation), coat development and quality, musculoskeletal development, shape and function, and more.  Rehabilitators are well aware that nutrition affects many internal organs and physiological functions in the young animals that are in crucial development stages and that those are extremely difficult to notice or monitor only through external factors and changes as mentioned above. 


Thus it helps to pay close attention to subtle signs, like overall energy and activity, interest in food, sleep amount and speed of waking, comfort moving, social interaction with litter/cage mates, and so forth.  It is helpful to document what you notice, even the minor signs, and how they have changed. Rehabilitators may have noticed such subtleties with some of the cases in 2019 and attributed them to other causes. They may have believed the issues were caused by more common factors, rather than indicators of possible nutritional disorders -- until patterns showed up with multiple animals and more obvious problems appeared.


The difficulties increase when animals are tiny and subtle symptoms can be challenging to notice or describe. A demanding rehabilitator workload and other responsibilities can add to the challenges -- as well as likely being tired, stressed, and short on time. Many of these subtleties or changes also may be easily missed with multiple caregivers working infrequent shift schedules. It is important to remember that many different factors can affect weight, growth and health and that there can be multiple possible causes of the problems. 


After many interviews, reviews of surveys, case reports, radiographs, etc. provided by rehabilitators who saw such nutritional disorders in 2019, WildAgain drafted the following chart that attempted to sort of the key signs and symptoms into stages. While it is certainly still in progress as more information becomes available, it may be useful to reference as one of the tools during a discussion about nutritional problems.


As mentioned earlier, many of the symptoms are very difficult to observe and could have different causes. That said, should those signs appear when the small mammal is being fed formula made with a SINGLE milk replacer powder, it seems prudent to quickly assess if the formula product, recipe, and preparation methods might be contributing factors.  One may then determine possible causes and if/what changes may help, such as blending milk powders to balance nutrition and minerals.

Health Problems from Wildlife

Corrections dealing with nutritional problems are easier, faster and have a far better chance of success when the young mammals arrived when older and in better health – and are in very early stages of any nutritional disorder. In general, there are more challenges rehabilitating extremely young mammals (i.e., neonates) and/or are presented to rehab with severely compromised health on arrival (e.g., severe injury, emaciation?, disease). If further health problems affecting multiple functions and organs develop and become more advanced due to nutritional problems that have occurred over a longer period of time, recovery is more difficult and more uncertain. In more severe cases, recovery may be less likely, especially for wild animals that need full function to survive independently on release to the wild. More information on cases, stages and possible actions are being prepared, and hope to be available shortly.


17. How do I know how much and how often to feed the wild babies to make sure they are getting enough daily calories?   


Wildlife rehabilitators work to estimate the number of feedings of a substitute milk formula that are needed per day to achieve a healthy, growing and thriving animal – especially when modifying formula recipes. Sources ranging from scientific research papers and publications to more informal social media postings provide various suggestions. Unfortunately, many of these sources provide widely varying instruction, little consensus, and very sparse references, which prompts a questionable level of confidence in the information. 


An easy explanation of the math used to calculate minimum energy requirements (kcals) per day is available to help reviewing formula – with sources. It is straightforward to calculate approximate feedings per day by knowing the weight of the animal, kcals in the formula and how much is being fed per feeding. See here LINK.


18. Wrap-up


WildAgain is very aware that there are many more questions about the milk replacer products and formulas, results seen in the mammals in rehabilitation, and ways to evaluate results. We also know the responses are incomplete, as the subjects are complex, products and methods are changing, and research is ongoing. More information is expected and will be posted on as it becomes available.



Thanks for your interest in the topic – and commitment to wildlife.





Allan and Shirley Casey, co-founders of WildAgain Wildlife Rehabilitation, Inc. in Colorado, have been licensed rehabilitators since 1986. They conduct research on a variety of rehabilitation related subjects, including nutrition, wildlife health, rehabilitation regulations, and trends. They have written 150+ articles for rehabilitation, veterinary and online publications, as well as the Squirrel Rehabilitation Handbook. The Caseys have no affiliation with any milk replacer company.

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