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Originally Posted by pstinard  Hi, I apologize profusely in advance. I promised in another thread to take a break in posting on nutrition articles, but I think I can make a couple of comments without being too controversial. I was able to access the original article cited by the Becker article: http://www.actavetscand.com/content/...015-0097-z.pdf
I looked at their table of results specifically searching for DNA content of the Hills products that were mentioned. Here is what I found: Hill's Prescription Diet R/D Feline Weight Loss Low Calorie Liver (Cat, Hill's Pet Nutrition). Ingredients: Pork Liver, Pork By-Products, Chicken, Chicken Liver Flavour. DNA analysis showed that the only DNA present was 100% from pork.
The critique of this result is that the only DNA present was from pork, and none from chicken, which is also on the label. My comments are that (1) The results posted in the paper are qualitative, not quantitative, so it's impossible to tell whether chicken DNA wasn't detected because there was no chicken in the cat food, or whether the chicken DNA wasn't detected because it was degraded during food processing, and (2) There was no DNA detected from species that were not on the label. Hill's Science Plan Tender Chunks in Gravy--Chicken (Cat, Hill's Pet Nutrition). Ingredients: Meat and animal derivatives (35% chicken). DNA analysis showed 3% pork DNA and 97% chicken DNA.
Again, the article's critique is that there should have been a lower percentage of chicken, and a higher percentage of other meat sources, since the label says 35% chicken. Again, my comments are that (1) The results are not quantitative--there is no guarantee that any of the DNA of any of the animal species wasn't degraded by the cooking process, (2) There was no DNA from species not listed on the label, and (3) At least the food was labeled as being a chicken product and contains chicken, perhaps a lot of chicken.
This is a very interesting study, and I think that it makes valid points for those foods for which DNA was detected from species that are NOT on the label. That could indeed result in food allergies for unsuspecting customers, violate labeling regulations, and be problematic to people who don't want to feed particular meat sources due to religious practices. I just wanted to point out some methodological flaws in the study. Just because the study didn't find the DNA for a particular species doesn't mean that the species meat isn't in the food. And the proportions of the DNA that they detected could be off due to how the food is made (possible DNA degradation).
The authors of this article cite another study of dry dog foods where the proteins were analyzed for their animal source of origin. That's a much more valid approach, especially since it's generally the proteins that cause allergic reactions. I'm going to check that article out right now. Again my apologies--Becker's description of the research article is fundamentally correct. It's just some of the conclusions of the original article that may be a little off. |
Here is a link to another article on dog food protein source contamination that was cited by the article above:
http://onlinelibrary.wiley.com/doi/1...jpn.12045/full. BTW, I find this article more valid than the one cited above because they used microscopic analysis of bone fragments to determine the species present, as well as DNA analysis. AND their main issue is with foods containing protein sources not on the list of ingredients, not with foods that don't appear to contain protein sources that ARE on the list of ingredients.
Unfortunately, this article doesn't name the brands that were tested, but they found that 10 out 12 foods tested contain protein sources not listed on the label. Now THAT is problematic for dogs with allergies, because these were supposed to be limited ingredient foods:
Summary
Failure to respond to commercial limited antigen diets can occur in dogs kept on a dietary trial for the diagnosis of adverse food reaction (AFR). The aim of this study was to assess twelve canine dry limited antigen diets (eleven novel protein diets and one hydrolysed diet) for potential contamination by ingredients of animal origin not mentioned on the label. The validity of the two methods adopted for the detection of such food antigens was also evaluated. Each dietary product was analysed by microscopy analysis using the official method described in Commission Regulation EC 152/2009 with the aim of identifying bone fragments of different zoological classes (mammalian, avian and fish) and by
polymerase chain reaction (PCR) for the identification of DNA of animal origin. Discrepancies between the results obtained by PCR and/or microscopy analysis and the ingredients listed on pet food packages were found. Only in two pet foods did the results of both analyses match the ingredients listed on the label. In the remaining ten samples, microscopy detected bone fragments from one or two unpredicted zoological classes, revealing avian fragments in six of ten samples followed by those of fish in five of ten and mammalian fragments in four of ten. In two samples, microscopy analysis identified a contamination that would have otherwise passed unobserved if only PCR had been used. However, PCR confirmed the presence of all the zoological classes detected by microscopy and also identified the DNA of an additional unexpected zoological class in two samples. Dogs might fail to respond to commercial limited antigen diets because such diets are contaminated with potential allergens. Both PCR and microscopy analysis are required to guarantee the absence of undeclared animal sources in pet foods.
Before ruling out AFR, a novel protein home-made diet should be considered if the dog is unresponsive to a commercial regimen.