Cat Microbiomes Stem From Diet
October 23, 2012

Diet Determines Feline Gut Microbiome

April Flowers for — Your Universe Online

What grows in the gut, for animals and people, is affected by diet. Beginning at birth, gut microbial colonies, known as gut microbiome, start forming. The composition of these colonies plays a big part in how the immune system develops and is linked to the later onset of metabolic diseases such as obesity.

Cats are carnivorous and common wisdom holds that the healthiest diet for them is one of high-protein. A new study from the University of Illinois set out to find out if this common wisdom is true. The results were published online in the British Journal of Nutrition.

"There are a lot of diets now, all natural, that have high protein and fat and not much dietary fiber or carbohydrates," said animal sciences researcher Kelly Swanson.

Swanson and his research team investigated the effect of the dietary protein and carbohydrate ratio on the gut microbiomes of growing kittens. Eight domestic shorthair female cats were randomly assigned one of two dry diets one month before they were bred. One group was given a high-protein, low-carbohydrate (HPLC) diet while the other was fed a moderate-protein, moderate-carbohydrate (MPMC) diet. The kittens were housed with their mothers until they were 8 weeks old and weaned. Then they were fed the same diet as their mother.

The 30+ kittens were housed in groups of two or three within the dietary-group cages. All the kittens were allowed into a common area furnished with toys and scratching posts to interact with each other and humans.

"It became quite a party right away," said Swanson. "It was a bit chaotic but fun as well."

The researchers selected 12 of the kittens to become part of the study, taking fecal samples at weaning and again at 4 and 8 weeks after weaning. The researchers extracted bacterial DNA from the fecal samples and used bioinformatics techniques to estimate total bacterial diversity.

"This was one of the first studies in cats to use sequencing to really lay out what is in the gut in regards to microbiota and apply it to nutrition," Swanson said.

Important differences in microbiome composition were found between the two groups. The levels of proteolytic bacteria — which break down protein — were higher for kittens on the HPLC diet, while levels of saccharolytic bacteria — which break down carbohydrates — were higher in the kittens on the MPMC diet. These results were exactly what the researchers expected to find.

The team also investigated the relationship between diet and physiology. The MPMC kittens had high levels of bifidobacteria, linked to higher blood ghrelin levels — which is a hormone that stimulates appetite and may have links to weight gain.

Bifidobacteria may also promote better gastrointestinal health as lower levels have been linked to inflammatory bowel disease in humans.

MPMC kittens had other bacteria that were found to have higher levels than the HPLC kittens, including lactobacilli, that has also been linked to gut health. A positive relationship between lactobacilli, blood cholesterol, and blood leptin levels was found by the research team. Leptin signals the body to stop eating when the stomach is full, so it is possible that there is a connection between lactobacilli and cholesterol metabolism, appetite and body weight regulation.

All of the kittens were healthy throughout the study, even though the HPLC kittens had lower levels of some health-promoting bacteria including bifidobacterium, lactobacillus, and megashaera.

The associations found in this study should be the basis for further research, according to Swanson.

"There were some interesting observations that could have applications for disease or the practical side of owning a pet," he said.

"The cat is fairly unique metabolically," he added, "But when it comes to gut microbes, there are a lot of similarities to other species. If you feed the bacteria in a cat, dog, or human colon the same substrate, there are probably going to be similar outcomes."