Can there be salmonella in raw food?

Yes, it is possible for it to become contaminated with Salmonella, but some people advocate avoidance first without considering at all the facts.

Firstly dogs have a very acidic stomach (pH ≤1), an environment that is not friendly to any bacteria. Salmonella cannot survive at that pH level and at minimum needs a pH of 4 or higher to grow. Optimal growth doesn’t occur until the environment reaches the pH range of 6.5-7.57.

Secondly, there are differences between the length of our digestive tract (8-9m) and that of a dog’s digestive tract (3-4m). This indicates a shorter transient time between intake and excretion and decreases the time that the bacteria have contact with our digestive system. The shorter the transient time the less likely it is that Salmonella can break through the gastrointestinal barrier and enter our system.

Also important to note is the differences in the digestion of carbohydrates (significant because of the high grain content in dry dog food). Humans have a-amylase, an enzyme dogs lack, in their saliva that starts digesting carbohy- drates as soon as they enter our system. Dogs do not start to digest any carbohydrates they eat until it reaches their stomach with the majority of digestion taking place in their small intestine4. The high percentage of carbohydrate in most dry dog food leads to situations where the food stays in the system longer (8-12 hours). However because a raw diet is meat based takes about half the time to digest (4-6 hours), thereby limiting the time that any possible bacteria may exposed to their system2.

Here at Mountain Dog Food preliminary testing is being carried out in an attempt to show what is occurring in the stomach of a dog during digestion. A solution of hydrochloric acid at a pH of 1, similar to that of the canine stomach, is prepared and samples of dog food (both raw and dry food) are added with the resultant pH being tested intermittently over time.

While both samples show changes to the pH level the dry food sample shows movement across the scale towards a pH of 6, whereas the raw food levels off at a pH of approximately 3. Since dry food takes longer to digest, and therefore remains in the stomach longer this trend towards a more basic environment may have an impact upon the digestion of the food. This may be significant since the pH of a dog’s stomach is one of the important barriers in Salmonella resistance. Results may give some indication of the differences between how dogs digest a raw meat based diet and a dry grain based one. While the findings may direct further study it is too early to tell if the results are statistically significant at this point.

One popular study done by Joffe and Schlesinger assesses the risk of Salmonella in dogs fed a raw diet. While the study does show positive results for Salmonella in 80% of the raw food and 30% of the stools sampled from dogs fed raw diets there are aspects that are overlooked in regards to these results and the study itself6. The size of the study (10 raw fed and 10 kibble fed dogs) and number of samples taken (one stool and one food sample per dog) are too small to be statistically significant. As well the results may be biased since the owners were aware of the studies purpose ahead of time and they were also responsible for collecting the samples. The paper fails to show if measures were taken to control how the food was thawed, holding temperatures (i.e. did the food sit out for extended periods at room temp beforesample was taken?), and sanitary practices surrounding feeding. Sanitation alone could be a huge contributing factor to the positive test result for Salmonella especially in the raw dog food. If feeding bowls, contact surfaces and utensils used were not properly cleaned after each meal bacteria could be introduced to fresh product that it comes into contact with. Independent tests done by PBR Laboratories on our raw food products have yet to this date show a positive test result for Salmonella.

It is also interesting to note that his findings give some credence the theory that a dog’s digestive system can handle exposure to Salmonella. Of the 8 samples of raw food that tested positive for Salmonella only one of the three positive stool samples correlates back to the same species of Salmonella found in the food. In the remaining dogs the Salmonella was either dealt with by their system and was not present in their stool or was already in their gut microflora and was expelled in their stool. The positive results in 30% of the stool samples for dogs fed raw does not come as a surprise seeing that 36% of healthy dogs, regardless of diet, have Salmonella in their digestive tract4. It was actually more surprising that none of the dogs fed a dry diet tested positive for Salmonella. Joffe states in his paper that feeding raw meat to dogs is a “public health concern”6. However, oral and anal swabs taken from some of our dogs exclusively fed a raw diet all gave negative results for the presence of Salmonella. Admittedly these results need to be replicated at a level that is statistically significant. However they do give evidence to contest his conclusion that dogs fed a raw diet are a health risk. His study fails to prove unequivocally that dogs fed a raw diet are a greater health concern than any other potential sources of contamination in our day-to-day environment. While we don’t discredit the basis behind his work we feel that more definitive and statistically significant findings need to be produced before proclaiming a public health concern.

Sources Cited:
  1. Baron, E.J. et al. (1994) Medical Microbiology. A Short Course. John Wiley & Sons, Inc. Pg. 329-342.
  2. Canine Nutrition – Volhard Holistic Care. April 8, 2003. http://www.volhard .com/holistic/artbywv.htm#nut
  3. CDC – Healthy Pets Healthy People. February 26, 2003. http://www.cdc. gov/healthypets/diseases/salmonellosis.htm
  4. Hand, M.S., Thatcher, C.D., Remillard, R.L., and Roudebush, P. (2000) Small Ani- mal Clinical Nutrition. Mark Morris Institute. Pg. 36-42,188.
  5. Herboid, J.R. (2000) What You and Your Clients Need to Know About Zoonotic Diseases: Rabies, Lyme Disease and Salmonellosis. North American Veterinary Conference 14:833-834.
  6. Joffe, D.J. and Schlesinger, D.P. (2002) Preliminary assessment of the risk of Sal- monella infection in dogs fed raw chicken diets. Can Vet J 43:441-442.
  7. Stiles, M.E. and McMullen, L.M. (1999) Nutrition and Food Science 361/363 – Food Microbiology. University of Alberta. Pg.196-209.
  8. Wills, J.M. and Simpson K.W. (1994) The Waltham Book of Clinical Nutrition of the Dog and Cat. Pergamon Publishers. Pg. 157-158.