A microbiome is a microbial community (bacteria, fungi, viruses and other tiny things) occupying a discrete habitat, such as the gastrointestinal (GI) tract of cats. We are just beginning to explore the roles played by bacteria and other microbes in maintaining the health of domestic cats (e.g., Inness et al. 2007, Janeczko et al. 2008, Suchodolski 2011). The GI tract of domestic cats supports a diverse bacterial community that directly influences cat health and nutrition (Simpson 1998, Jergens 2002, Guilford and Matz 2003, Weese et al. 2004). The feline duodenum (the part of the gut that the stomach empties into) harbors up to 100 million cells per gram of poop, and is dominated by bacteria that live in environments with low levels of oxygen (e.g., Johnston et al. 1993, Papasouliotis et al. 1998, Johnston et al. 2001).
Cats, like humans and most other mammals, are colonized by bacteria during delivery and birth. However, unlike people, each kitten arrives encased in an amniotic sac, which is a jelly-like membrane filled with clear fluid. Upon birth, mother cats (also called queens) begin licking the kitten and tear open this sac so that the kitten can breathe air. Once exposed to the outside world, the kitten’s microbiota is altered by all it interacts with and eats, so that its microbial community shows dramatic changes in species composition and structure during weaning from mother’s milk to the digestion of a high protein diet, whether prey, kibble or can (Vester et al. 2009).
Most research on the feline intestinal microbiome has understandably focused on effects of diet (e.g., Lubbs et al. 2009, Vester et al. 2009, Barry et al. 2012, Bermingham et al. 2013, Hooda et al. 2013). It may be that the high amount of carbohydrates found in some commercial cat foods is problematic for cats. There are several studies currently being conducted by us as well as other researchers to examine how feeding cats a raw diet affects their microbiome. If you're curious to see how your cat's microbiome measures up to those of other cats, check out our gut health microbiome test kits for cats.
Evolutionary history matters too
In addition to diet, evolutionary history affects the composition of the gut microbiome. For example, a study of gut bacteria in a wide range of mammals conducted by Ley et al. (2008) found that both diet (herbivore, omnivore, and carnivore) and taxonomic grouping of the mammal (such as orders: primates, insectivora, and carnivora) influence bacterial diversity patterns. Although order Carnivora, a taxonomic grouping that includes the cat family, contains many omnivores (such as dogs, bears and raccoons) and even some herbivores (like pandas), cats are strictly carnivorous (meat eating). In nature they obtain 98% of their energy from animal protein and fat, and about 1-2% from carbohydrate sources such as glycogen. Cats are unable to make certain amino acids and require a diet that is high in protein. Depending on the size of the cat, they will consume all or some of the carcass of prey that they've killed.
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