I have seriously failed at writing a blog post weekly. I will try to do a better job of keeping the blog up to date.
I posted on Facebook earlier this week, the following link from a publication that comes out to petfood manufacturers. http://www.petfoodindustry.com/Research_Notes/Extruded_vs__raw_vs__cooked_beef-based_diets_for_cats.html regarding one of our research studies that was published in the Journal of Animal Science this year. I was thrilled to see our study reach those in the industry. It's taken a good deal of time to get this particular study published and I figured there would be readers very interested in our results.
A couple pieces of background to put on the table first. This study was a collaborative effort with the University of Illinois (I hold an adjunct appointment there and work with many graduate students). This study was one of several that a very talented graduate student worked on with us. Much of her Masters and Ph.D research have focused on exotic cat nutrition; however, this was one that we felt was necessary to develop some much needed research in the field. Secondly, it was in domestic cats. Cats are a bit easier for us to conduct research on, especially the big exotic ones because they are housed individually and it's easy to collect samples. Canid species are almost always housed in groups and it makes sample collection a bit more difficult. In addition, since cats are true obligate carnivores, they serve as the best model to study raw diets (at least right now as raw diet research is truly in an infancy stage). We have hopes to develop our efforts with canids but for now, we are focusing on cats. So many questions about raw diets need answered and researched and it would take my entire career to barely scratch the surface. I can only hope that other researchers will join the ranks so we can get some much needed answers.
So, with that in mind, the objectives of this study were to determine differences in the digestibility, fecal characteristics, urine characteristics, and serum chemistry of 9 domestic cats fed 3 different diet treatments. The dietary treatments were the raw beef-based diet that we feed to our cats at the zoo (Raw); the same diet but cooked (cooked) and a high quality grain-free kibble cat food (kibble).
Table 1. Nutrient composition of the diet treatments (dry matter basis)
Nutrient Raw Cooked Kibble
Moisture, % 70.7 70.8 5.7
Protein, % 52.5 52.0 57.0
Fat, % 20.5 18.3 17.4
Energy, kcal/g 5.0 4.7 4.2
Table 2. Digestibility of the the treatment diets
Item Raw Cooked Kibble
Organic matter, % 90.5 88.5 83.9
Protein, % 93.3 92.9 81.6
Fat, % 95.5 95.3 91.3
Energy, % 91.5 89.8 84.7
Table 3. Fecal characteristics
Item Raw Cooked Kibble
fecal output (g DM) 6.7 7.2 13.0
Ammonia 69.4 72.0 190.4
total BCFA 17.6 16.8 43.7
In respect of blog length, I'm not including the urine measures or the blood metabolites as there were no major significant differences detected among the diet treatments and results were within reference ranges for cats.
OK, so what does that data tell us? Obviously the diets had similar nutrient compositions (Table 1) but the nutrients were digested different (Table 2). Organic matter digestibility is a term that we nutritionists use to essentially look at the overall diet digestibility (taking into account all nutrients except minerals). It's pretty obvious that the raw diet was better digested by the cats. Although it was better digested than the cooked diet, those numbers did fail to reach statistical significance (were only about 2% different for the most part). The scientists out there reading this will find that to be of important note. That said, the raw diet had nearly a 15% improvement in protein digestibility compared to the kibble. This to me is one of the most important pieces as we consider protein quality. We want the protein to be better digested.
When looking at Table 3, there were some very important pieces there as well. Fecal output measured as grams of dry matter, was lower in the cats fed raw and cooked. This was likely due to the fact that the cats fed the kibble diet consumed significantly more dry matter than the cats on the raw or cooked diets. More importantly, fecal ammonia and BCFA (branched chain fatty acids) were much lower in the cats fed either the raw or cooked diets compared with the kibble. Ammonia and BCFA are putrefactive compounds produced during colonic fermentation of endogenously produced and non-absorbed amino acids. This was likely a direct result of the lower digestibility of protein for the kibble diet (more amino acids and proteins reaching the colon for fermentation).
Those of you that feed raw, are cheering (I can hear you). We are following it up with another study that included raw, kibble, canned and whole prey in both domestic cats, and in African wildcats. Those data are currently being analyzed and we hope to be presenting those data this summer. While we can't completely translate this data to dogs, it's likely a pretty good chance we'd see similar results in other carnivore species including dogs.
K.R. Kerr, B.M. Vester Boler, C.L. Morris, K.J. Liu, and K.S. Swanson. 2012. Apparent total tract energy and macronutrient digestibility and fecal fermentative end-product concentrations of domestic cats fed extruded, raw beef-based, and cooked beef-based diets. Journal of Animal Science: 90: 515-522.