You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

As dogs get older there is a change in the composition and number of micro-organisms in the gut. These changes  could increase the risk of nutritional disorders, or diseases such as bacterial overgrowth.

There is a growing amount of evidence to show that as dogs get older the type and numbers of bacteria in the intestinal tract change. In a one study*  it was shown that there was a significant increase in the numbers of both aerobic (24% increase) and anaerobic (41% increase) bacteria when comparing faecal samples from 1 year old and 11 year old Beagles, but the number of enterobacteria was decreased. Clostridia (344% increase) and lactobacilli (118% increase) showed the greatest increase. Altering the diet by adding fructooligosaccharides (a non-digestible carbohydrate which is fermented  by bacteria in the gut) for 8 weeks  had a significant effect on the bacteria present, notably by increasing the number of eubacteria .

These findings have resulted in the inclusion of prebiotics in  pet foods  because high numbers of some bacteria can effect health eg increasing numbers of non-pathogenic strains of E coli may help inhibit the development of pathogenic bacteria. In other words, dietary manipulation may be used to create a gut population of "beneficial" bacteria and reduce the presence of potentially harmful bacteria. Further studies are needed to confirm if they actually are beneficial

* (Kearns et al "Microbial Changes in Aged Dogs" in Recent Advances in Canine and Feline Nutrition" (1998), The Iams Company)

Updated January 2016