Journal
JOURNAL OF NUTRITION
Volume 151, Issue 12, Pages 3637-3650Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jn/nxab308
Keywords
feline; protein concentrations; feces; microbiota; fecal pH; proteolysis; mucin foraging
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Funding
- Hill's Pet Nutrition, Inc.
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This study evaluated the effects of different protein:carbohydrate ratios in foods on the gut microbiota and functional attributes in healthy adult cats. The results showed that consuming high-protein food (P55) led to increased mucin glycan foraging and amino acid metabolism in the gut microbiota, resulting in higher fecal pH, ammonia, and branched-chain fatty acids.
Background Relative levels of dietary protein and carbohydrate intake influence microbiota and their functional capabilities, but the effect has not been well documented in cats. Objectives The impact of 3 foods with different protein:carbohydrate ratios on the gut microbiota and functional attributes in healthy adult cats was evaluated. Methods Male and female cats (n = 30; mean age: 5.1 y; mean body weight: 5.26 kg) were fed 1 of 3 foods [P28 (28.3% protein, dry matter basis), P35 (35.1%), and P55 (54.8%)] for 90 d in a Williams Latin Square design. Each food had a 1:1 ratio of animal (dried chicken) to plant (pea) protein; protein replaced carbohydrate as protein level increased. Fecal microbiota and their functional capability were assessed with 16S sequencing and the Kyoto Encyclopedia of Genes and Genomes database, respectively. Results Fecal pH, ammonia, and branched-chain fatty acids (BCFAs) were higher when cats consumed P55 food than when they consumed P28 and P35. Clear separation of samples between P28 and P55 based on bacterial genera was observed, with partitioning into saccharolytic and proteolytic functions, respectively. Significantly higher alpha diversity was seen with P55 than with P28 and P35. Amino acid metabolism, mucin foraging pathways, and urea metabolism were higher with P55 than with P28, whereas feces from cats fed P28 had higher concentrations of carbohydrate-active enzymes and enzymes involved in SCFA pathways than with P55. Bacterial genera that showed positive associations with amino acid catabolism also showed positive associations with mucin degradation. Conclusions Despite higher protein digestibility and less protein arriving to the colon, when healthy adult cats consumed the highest level of protein (P55), their gut microbiota exhibited higher mucin glycan foraging and amino acid metabolism, leading to higher fecal pH, ammonia, and BCFAs. This is likely due to lower availability of carbohydrate substrates and dietary fiber as protein replaced carbohydrate in the food.
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