My answer to this question may surprise people; however, I do not routinely recommend probiotic use for most normal/healthy dogs and cats (or any species that I work with). I save probiotics for those times when the gut microbiota becomes unbalanced. I use them as a tool to help "right" the gut.
The gut microbiota is a complex assortment of microorganisms that inhabit all mammalian gastrointestinal tracts with a composition that is host specific. This microbiota is involved in a wide array of host physiology including nutrition, gut health, behavior, stress response, inflammatory responses and immunity; therefore, maintaining an optimal balance is imperative to host health. A balanced microbiota is an amazing phenomenon and the beauty is that these well balanced systems can handle typical insults to the gastrointestinal tract and right themselves back into balance. One of my goals in nutrition is to provide foods that promote that well balanced microbiota, opposed to continually having to provide the live microorganisms through probiotic use. I also have growing concerns regarding the transfer of antibiotic resistant genes to and from probiotic microorganisms. There is increasing research indicating that antibiotic resistance is present in species of some probiotic strains including enterococcus faecium, lactobacillus and lactococcus spp. This may or may not pose a significant risk; however, it is evidence enough for me to keep a mindful eye on the research and where the industry is moving.
That being said, of course dogs being what they are, tend to eat things they shouldn't. In addition, antibiotic treatments also can pose threats to the microbiota environment. These insults to the gut may cause that balance to sway and result in diarrhea and digestive function loss. This is when I want to use probiotics and prebiotics. In addition, I will often recommend probiotics for older dogs that are naturally losing some digestive function due to age. I do keep probiotics on hand and I travel with them to trials. It always seems that our dogs tend to have digestive issues while we are competing at shows or trials. However, in part this may be due to stress (like it or not). Currently, I prefer the Prostora product made by Iams because that product contains Bifidobacteria rather than the Lactobacillus species that are most often included in probiotics.
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