Fuller of the
AFRC Institute of Food Research, Reading Laboratory, Shinfield,
UK wrote the following in 1989: “There is good evidence that
the complex microbial flora present in the gastrointestinal
tract of all warm-blooded animals is effective in providing
resistance to disease. However, the composition of this
protective flora can be altered by dietary and environmental
influences, making the host animal susceptible to disease
and/or reducing its efficiency of food utilization. What we
are doing with the probiotic treatments is re-establishing the
natural condition which exists in the wild animal but which
has been disrupted by modern trends in conditions used for
rearing young animals, including human babies, and in modern
approaches to nutrition and disease therapy. These are all
areas where the gut flora can be altered for the worse and
where, by the administration of probiotics, the natural
balance of the gut microflora can be restored and the animal
returned to its normal nutrition, growth and health status.”
So, in other words, probiotics can and do restore balance to
the microorganisms of the digestive tract if they should
suffer negatively due to environmental, dietary, or disease
related stress.
Given the benefits, it would seem
prudent to include probiotics into the canine diet - and it
is. The problem arises, however, when they are included as an
ingredient in a commercially prepared diet and the inevitable
degradation caused by processing, extrusion, and storage.
While there are several studies
that illustrate this point, perhaps the best was conducted by
J Scott Weiss and Luis Arryo, Department of Clinical Studies,
Ontario Veterinary College, University of Guelph, Guelph,
Ontario in 2003. The goal of the study was to “isolate,
enumerate, and identify probiotic bacteria in pet foods
claiming to contain probiotics” and, to do so, 19 different
pet foods that used the word “probiotic” on their labels
were purchased right off store shelves. Perhaps, needless to
say, the results were not good. The abstract reads as follows:
“Nineteen commercial pet foods claiming to contain
probiotics were evaluated. Selective bacterial culture was
performed to identify organisms that were claimed to be
present. Twelve diets claimed only to contain specific
bacterial fermentation products, which does not necessarily
indicate that live growth would be expected, but these
products also included the term “probiotic” somewhere on
the package, suggesting that live, beneficial organisms were
present. No products contained all of the listed organisms,
while 1 or more of the listed contents were isolated from 10
out of 19 products (53%). Eleven products contained
additional, related organisms including Pediococcus spp,
which was isolated from 4 products. No relevant growth was
present in 5 (26%) products. Average bacterial growth ranged
from 0 to 1.8 × 105CFU/g. Overall, the actual
contents of the diets were not accurately represented by the
label descriptions.”
Their further observations
included “Interpretation of these results is confounded
somewhat by the questionable labelling of some products”
and “Lactobacillus acidophilus was purported to be
present in 13 diets, yet it was not identified in any”
and “Overall, commercial pet foods that claim to contain
probiotics appear to contain very low numbers of viable
organisms, and often do not contain the species listed on the
label.” Comment, here, is probably unnecessary.
An earlier study which, rather
than testing commercial diets themselves, tested probiotics as
an additive ingredient and methods of incorporation into a pet
food. Conducted by Vincent Biourge, Céline Vallet, Anne
Levesque, Renaud Sergheraert, Stéphane Chevalier, and
Jean-Luc Roberton and published in The Journal of Nutrition in
1989, The Use of Probiotics in the Diet of Dogs looked
at a very specific probiotic, Bacillus CIP 5832, and is
a common ingredient in livestock feed. The study was conducted
in two ways - first adding CIP 5832 to a dog food mixture
prior to extrusion and then, second, adding the probiotic post
extrusion as a powder coating. Initially, both methods of
application were to be followed over a 12 month period to
ascertain viability during storage.
Sadly, in the first application
(the addition of the probiotic pre-extrusion), “the
extrusion-expansion and drying process resulted
thus in the loss of >99 % of the spores” and the
conclusion was reached that “Bacillus CIP 5832
should thus not be included in the diet before the extrusion-
expansion and drying process.”
The application of CIP 5832 fared
better when dusted (or powder coated) on to the kibble after
extrusion and drying with an ~60% viability immediately and an
~25% degradation over 12 months. The second method of
inclusion was deemed successful and concluded that “In
summary, these studies demonstrated that the addition of Bacillus
CIP 5832 to a dry dog food was feasible under certain circumstances.”
This, of course, necessarily lead to two questions - Are the
“certain circumstances” mentioned followed by commercial
pet food manufacturers ( given the Weiss study previously
mentioned, it seems not!) and was the manner of storage used
to evaluate viability after 12 months akin to what would be
found in shipment, warehousing, retailing, and in the consumer
home? Both leave room for doubt.
As it has been shown that
probiotics have not been incorporated into dry dog food in
such a way as to live up to consumer expectation and that
labeling may be deemed at best, incorrect, using the inclusion
of probiotics as a criteria for dog food selection may not be
in the best interest of the purchaser. Far better to add a
certified probiotic supplement at time of feeding - that way
you will really know what you are getting.
