Whole Prey For Dogs And Cats
Many Pet parents are interested in feeding their dogs and cats whole prey. Some feed them whole while others grind them before feeding. Quail, Duck, Rabbit, and Chicken are the more common options. While this has been common for snakes it is still gaining steam in the dog and cat space. That being the case I feel it is important to look at the actual nutritional value of said prey.
Whole Prey Minerals
The first two tables compare the mineral content of the whole prey with the AAFCO Guidelines.
As you can see from the tables below each of the whole prey is deficient in a variety of minerals namely Potassium, Sodium, Chloride, Magnesium, Copper, Manganese, and Zinc. This also isn’t a complete list of minerals as iodine and selenium were left out of the study. While some are relatively close to the minimums others are much further away. So even if we grant the premise that you don’t need as much due to greater bioavailability it could very well still fall short. This is why if you want to feed a whole prey diet or even PMR; rotation and variety are extremely important. It is also important to note that the actual nutritional value of various whole prey is different than what they were even twenty years ago much less 100 or 200 years ago. This doesn’t just apply to factory-farmed meat it goes for everything we provide our pets.
Also of importance is the Omega 6 to Omega 3 Ratio. They are all very high with Chicken and Duck being the highest. While AAFCO has no minimum, the maximum is 30 to 1. Most people believe that these numbers are far too high, and advocate for a ratio somewhere between 1:1 and 5:1. The reason being is that high ratios contribute to inflammation. One way to bring the ratio down is to incorporate the occasional whole sardine or other fish to their diet. You could also give it to them as a snack or reward. Many species of fish are also a valuable source of Iodine, so it also lowers the risk of developing an iodine deficiency. 
Whole Prey Amino Acids
The next three tables look at the Amino Acids. The first two look at the amino acid content of the prey, while the third looks at amino acid digestibility.
Given the amount of protein provided by the prey it should comes as little surprise that they exceed the minimum requirements, with the only exception being Taurine for cats. Taurine is not currently considered essential for dogs. This could very well change in the coming years as industry and science look into DCM. This happened almost 30 years ago in cats.
The amount required by AAFCO for cats is different for dry and wet food .1 and .2 The stillborn Rabbit and 1-3 Day old Chickens are just barely above the standard. While the rest of the Rabbits and Duck are well below the standard for Cats. Some of them are above the NRC standard for highly purified diets.
As for the Amino Acid Digestibility all of them performed well for the most part. With Cystine being an exception. The Quail performed the worse out of all of the prey. Taurine is of concern for cats as the prey particularly the rabbits, duck, and 1-3 days old chickens were already on the lower end.
Taurine Deficiency
Taurine deficiency leading to DCM has been previously reported in 70% of 22 young domestic cats fed entire ground rabbit (unskinned, undressed) for periods longer than 10 months. However, the age of the rabbits and taurine concentrations were not reported by the authors. The authors did report low dietary vitamin E which can contribute to Taurine losses during processing.
In a more recent study, they found that the Taurine Content of Fresh Rabbits with the GI Tract was .05% while without the GI Tract is was .07%. In Frozen Rabbit with the GI Tract, it was .05% with the GI Tract and .07% without the GI Tract on a dry matter basis. This is below the .1% and .2% of AAFCO for Dry and Wet foods.
“Some samples would have met the NRC recommended minimum for “highly digestible purified diets” (0.04–0.053% DM depending on life stage); however, these diets are typically only used in research settings, generally provide taurine in the crystalline form, and are likely of limited relevance to the needs of pet cats eating other types of diets. Although the requirement for taurine of cats consuming prey remains unknown, it seems unlikely that it would be less than that for commercial kibble diets due to the indigestible nature of certain components of the carcass.” (Owens 2021)
They also looked at the specific organs and found the following concentrations of Taurine on a dry matter basis,
Rabbit Kidney .07%
Rabbit Thigh .03%
Rabbit Heart .59%
Rabbit Brain .08%
Rabbit Lung .19%
Rabbit Liver .01%
“The low concentrations of taurine in rabbit, regardless of sample type and storage conditions, would very likely be physiologically significant if fed in large proportions or as the sole diet. … This could result in negative clinical consequences if cats are fed unsupplemented rabbit exclusively or as a large proportion of the diet but may not:” be of consequence in a wild-type setting as cats do not consume rabbit exclusively in the wild even when they constitute a larger percentage of the diet. Perhaps the consumption of additional and varied prey species is sufficient to meet overall needs. … It remains unknown if supplementation of taurine to concentrations recommended for either dry extruded or canned diets is sufficient to maintain normal taurine status of cats consuming whole-prey diets generally or rabbit specifically.” (Owens 2021)
All of that being said I would highly recommend rotation of their diet so your cat can get more taurine from the diet. This would also go for raw foods where rabbit is the primary ingredient. I would even recommend it for dogs even though AAFCO, NRC, and FEDIAF label it a nonessential Amino Acid.
Digestibility of Different Chicken Products
Now the next two tables look at the digestibility of different foods. This is extremely important as it is a factor in how the guidelines were developed.
The NRC guidelines are largely based on studies using highly purified ingredients with extremely high availability and digestibility. This, however doesn’t translate to pet foods.
That being said the next table look at the digestibility of different Chicken products. The study was conducted on Chicken Meal, Retorted Chicken, Steamed Chicken, and Raw Chicken.
Steamed Chicken performed the best with Raw Chicken and Retorted Chicken not far behind. While Chicken Meal performed the worst.
“In conclusion, this study provides the true nutrient digestibility data of four chicken-based ingredients intended for use in dog and cat foods . . . According to our data, the chicken meal has the lowest nutrient and AA digestibility and may not be sufficient if used as the sole protein source, when the cat or dog is fed to meet the minimum protein recommendations of AAFCO or NRC.” (Oba 2019)
“In contrast, AA digestibility was highest for steamed chicken, out-performing all other protein sources tested. AA digestibility of raw and retorted chicken-based proteins were slightly lower than that of steamed chicken, but still high-quality proteins. This study demonstrates the importance of in vivo testing to evaluate protein-based ingredients, as raw material and processing methods can greatly affect their protein quality and energy content.” (Oba 2019)
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Just Food for Dogs Digestibility
The next study was funded by Just Food for Dogs. It looked at the digestibility of their foods.
The researchers found that the modified Atwater factors (3.5, 8.5, and 3.5 kcal/g for protein, fat, and digestible carbohydrate, respectively), May underestimate the energy content of foods that are highly digestible. The food all performed well averaging in the mid to high 80s for the digestibility of amino acids which is an important measure of digestibility. With the lowest averaging 85.57%.
“Although statistical differences were observed among foods tested in this study, all foods performed very well. All foods tested had very high AA digestibility, with most exceeding 85% and some over 90%. Additionally, the TMEn data suggest that the predictive equations for ME recommended by NRC (2006), Atwater factors, or modified Atwater factors underestimate the energy content for most foods tested so that their use for pet foods made with human-grade ingredients is questionable.” (Oba 2020)
Now the above studies were all conducted using precision-fed cecectomized rooster assay. So it might not be entirely accurate as a means of measuring the true digestibility of the food when it is applied to our dogs or cats, but it does provide valuable insights.
Note on Digestibility
When comparing digestibility, it’s important to note the fiber content of the foods being compared. So while the poop may be smaller, this doesn’t necessarily indicate that your dog or cat is better at digesting the food. It might just be a result of more or less fiber in the food.
It does however demonstrate the importance of ingredient quality. It does demonstrate that Steamed, Raw, and Retorted Chicken is much more digestible than chicken meal. One other thing of note is the implication that the Modified Atwater values might be high for raw or gently cooked food using higher quality ingredients.
References
Kerr KR, Kappen KL, Garner LM, Utterback PL, Parsons CM, Swanson KS. Commercially available avian and mammalian whole prey diet items targeted for consumption by managed exotic and domestic pet felines: true metabolizable energy and amino acid digestibility using the precision-fed cecectomized rooster assay. J Anim Sci. 2014 Oct;92(10):4478-85. doi: 10.2527/jas.2013-7246. Epub 2014 Aug 22. PMID: 25149332.
Kerr KR, Kappen KL, Garner LM, Swanson KS. Commercially available avian and mammalian whole prey diet items targeted for consumption by managed exotic and domestic pet felines: macronutrient, mineral, and long-chain fatty acid composition. Zoo Biol. 2014 Jul-Aug;33(4):327-35. doi: 10.1002/zoo.21147. Epub 2014 Jul 14. PMID: 25043384.
Oba PM, Utterback PL, Parsons CM, de Godoy MRC, Swanson KS. Chemical composition, true nutrient digestibility, and true metabolizable energy of chicken-based ingredients differing by processing method using the precision-fed cecectomized rooster assay. J Anim Sci. 2019 Mar 1;97(3):998-1009. doi: 10.1093/jas/sky461. PMID: 30535325; PMCID: PMC6396239.
Oba PM, Utterback PL, Parsons CM, Swanson KS: True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay. Journal of Animal Science 2020; 4:442-451.
Owens TJ, Fascetti AJ, Calvert CC and Larsen JA (2021) Rabbit Carcasses for Use in Feline Diets: Amino Acid Concentrations in Fresh and Frozen Carcasses With and Without Gastrointestinal Tracts. Front. Vet. Sci. 7:592753. doi: 10.3389/fvets.2020.592753