top of page

Studies with Cats

Multiple studies were published in New Zealand from 2013 – 2019 by researchers at Massey University or associated with Ag Research, examining the influence of diet on the faecal microbiota of cats.

Funding: these studies were funded by the Massey University Research Fund, AgResearch and financial contributions were made from Bombay Petfoods Ltd., K9 Natural Ltd., and ZiwiPeak Ltd.

The publishers state that the funders did not contribute to study design, analysis or interpretation of the results.

Sample: Cats in the studies were colony housed. Eight queens were randomly allocated to one of two diets. Commercially available dry (Diet A) and wet canned food (Diet B) diets were utilised in this study. (n = 4 per diet). Each queen was mated, producing a total of 20 kittens.

From week 0 to 4, kittens received milk from their dam exclusively. At 4 weeks of age, the kittens were randomly assigned to one of the two diets (canned or kibble), and were weaned onto solid food in a gradual manner. At week 8, kittens were fully weaned, and were randomly allocated into 4 dietary treatment groups (n = 5 per treatment) and fed either Diet A (dry) (B-A or A-A) or Diet B (wet) (B-B or A-B).

Dry diet: moderate protein: fat: carbohydrate diet

Canned diet: high protein: high fat: low carbohydrate diet

STUDY: 2013, randomised controlled trial

Aim: to investigate the effects of pre- and post-weaning diet on the composition of faecal bacterial communities and adipose expression of key genes in the glucose and insulin pathways in the cat.

Key findings:

  • despite high faecal microbial diversity in pregnant queens, the pre-weaning diet had no effect on faecal microbiota composition in offspring

  • gene expression levels in blood and adipose tissues were altered by pre-weaning diet.


Relevance: This suggests that the maternal influences on gene expression are long lasting whereas its effects on microbial populations may be relatively short-term despite their relative stability over the lifetime of the individual.

STUDY: 2016, randomised controlled trial

Aim: The aim of the present study was to investigate the effects of pre- and post-weaning diets (kibbled or canned) on the composition and function of faecal microbiota in the domestic cat by shotgun metagenomic sequencing and gene taxonomic and functional assignment using MG-RAST.

Key findings:

  • Post-weaning diet had a dramatic effect on community composition; 147 of the 195 bacterial species identified had significantly different mean relative abundances between kittens fed kibbled and canned diets.

  • The kittens fed kibbled diets had relatively higher abundances of Lactobacillus (>100-fold), Bifidobacterium (>100-fold), and Collinsella (>9-fold) than kittens fed canned diets.

  • There were relatively few differences in the predicted microbiome functions associated with the pre-weaning diet.

  • Post-weaning diet affected the abundance of functional gene groups. Genes involved in vitamin biosynthesis, metabolism, and transport, were significantly enriched in the metagenomes of kittens fed the canned diet.


Relevance: The impact of post-weaning diet on the metagenome in terms of vitamin biosynthesis functions suggests that modulation of the microbiome function through diet may be an important avenue for improving the nutrition of companion animals.

STUDY: 2018, 5- year longitudinal study

Intervention: The researchers aimed to study the long term effects of feeding the two commercial diets (kibbled and canned), as allocated, on the colony kittens aged 5 years old. In particular, the researchers examined (a) microbial composition changes due to aging, (b) impact on body composition, and (c) effect on insulin sensitivity in the aging cat.

Key findings:

  • both diet and age affected faecal microbial composition

  • age correlated with changes in body composition

  • type of diet had no effect on body composition

  • insulin sensitivity was not affected by age nor diet. But the insulin sensitivity index appeared to be higher in kibble-fed cats

  • ·Key microbial families in cats, in parameters related to crude protein digestion in the cat: Peptostreptococcaeae, Eubacteriaceae, and to a lesser extent Fusobacteriaceae and Peptococcaceae.


Relevance: Results may change as the cats age (>7 years old). All cats had a good body condition score, which may have affected the results.

STUDY: Further research at Massey University on faecal microbiota

Aim: Faecal metagenomic DNA was extracted and shotgun sequenced. Sequences were analysed using the Metagenomics Rapid Annotation using Subsystem Technology to determine the relationship between Gammaproteobacteria abundance and specific gene functions.

Key findings:

  • Gammaproteobacteria were not highly abundant overall BUT significantly more abundant in cats fed the wet diet.

  • Species-level Gammaprotoeobacteria compositions were highly similar.

  • The most prominent taxa associated with the wet diet were Bacteroides, Fusobacterium and Clostridium. Lactobacillus and Bifidobacterium were highly abundant in kittens fed the dry diet.

  • Species of Gammaprotoeobacteria were highly correlated with the abundance of specific genes involved in transport and secretion systems.


Relevance: diet predominantly differentiates the composition and function of gastrointestinal microbiota in the cat. Their results suggest that Gammaprotoeobacteria may fill unique ecological niches in the healthy cat gastrointestinal microbiome when fed wet diets.


​Bermingham EN, Kittelmann S, Young W et al., 2013, “Post-Weaning Diet Affects Faecal Microbial Composition but Not Selected Adipose Gene Expression in the Cat (Felis catus)”, PLoS ONE, vol. 8(11), e80992.

Young, W., Moon, C., Thomas, D. et al. 2016, “Pre- and post-weaning diet alters the faecal metagenome in the cat with differences in vitamin and carbohydrate metabolism gene abundances”, Scientific Reports, vol. 6, art. No. 34668

Bermingham EN, Young W, Butowski CF et al. 2018, “The Fecal Microbiota in the Domestic Cat (Felis catus) Is Influenced by Interactions Between Age and Diet; A Five Year Longitudinal Study”, Frontiers in Microbiology, vol. 9, pp 1231.

Moon, CD, Young, W, Thomas, DG et al. “Gammaproteobacteria abundance and specific gene functions are highly correlated in the faecal microbiota of the domestic cat fed a canned or kibbled diet”, Ag Research Massey University


Design: Ag Research randomised controlled trial, cross over design feeding trial

Funding: this study was funded by the NZ government & NZ Premium Petfood Alliance (K9 Natural, Ziwi and Bombay Petfoods). The authors claim no non-financial competing interests.

Sample: 12 neutered DSH cats between 2–8 years of age

Aim: to determine the effects of adding plant-based dietary fibre to a high animal protein and fat diet.

Intervention: cats were fed three complete and balanced diets in a cross-over design for blocks of 21 days: raw meat; raw meat plus fibre (2%, 'as is' inclusion of inulin and cellulose) and a commercially available Kibble diet. A commercially available canned diet was fed for 21 days as a washout phase.

Key findings:

  • Diet significantly affected all faecal parameters measured.

  • The addition of dietary fibre to the raw meat diet was found to reduce apparent macronutrient digestibility, increase faecal output, pH and score. Faecal output was greatest in the Kibble diet, both on an ‘as is’ and DM per day basis.

  • Faecal pH was lower in Kibble compared to both Raw and Raw+Fibre dietary treatments.

  • Bacterial diversity: Assessment of alpha diversity found that there was a trend (P = 0.08) for cats during the Kibble dietary treatment to have a lower faecal diversity than the Raw. The Raw+Fibre dietary treatment resulted in an intermediate level of alpha diversity to the Raw and Kibble.

  • Bacteriome composition: of the 51 bacterial taxa identified in the study, 31 bacterial taxa were significantly affected by diet.

  • Prevotella was found to dominate in the Kibble diet, Clostridium and Fusobacterium in the Raw diet, and Prevotella and a group of unclassified Peptostreptococcaceae in the Raw+Fibre diet.


Relevance: diets of different macronutrient proportions can strongly influence the faecal microbiome composition and metabolism, as shown by altered organic acid concentrations and faecal pH, in the domestic cat. The addition of 2% of each fibre to the Raw diet shifted faecal parameters closer to those produced by feeding a Kibble diet.

Reference: Butowski CF, Thomas DG, Young W et al. 2019, “Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus)”, PLoS One, vol. 14(5): e0216072.

Study: Cats and diet and Diabetes

Aim: To assess the associations of environmental risk factors with diabetes in cats.


Animals: Cats with a diagnosis of diabetes (n = 396) insured by a Swedish insurance company during years 2009-2013, and a control group (n = 1670) matched on birth year.


Design: A web-based questionnaire was used in a case-control study.   The survey contained questions related to eating behaviour, feeding routine, general health and other factors.


Key findings:

  • Indoor confinement, being a greedy eater, and being overweight were associated with an increased risk of diabetes.

  • In cats assessed by owners as being normal weight, there was an association between eating predominantly dry food and an increased risk of diabetes.


Relevance:  The association found between dry food and an increased risk of diabetes in cats assessed as normal weight by owners warrants further attention.


Peer reviewed


No conflict of interest declared

Reference: Öhlund, M Egenvall, A, Fall T et al.  2017, “Environmental Risk Factors for Diabetes Mellitus in Cats”, Journal of Veterinary Internal Medicine, vol. 31(1), pp 29-35

Review: Cats as obligate carnivores and diet

Zoran, DL 2002, ‘The carnivore connection to nutrition in cats’, Journal of the American Veterinary Medical Association, vol. 221, no. 11, pp. 1559-67.

  • The review explains what it means metabolically and nutritionally to be an obligate carnivore.

  • Cats are obligate carnivores that rely on nutrients in animal tissues to meet their specific and unique nutritional requirements.

  • In their natural habitat, cats consume prey high in protein with moderate amounts of fat and minimal amounts of carbohydrates.  They are metabolically adapted for higher metabolism of proteins and lower utilisation of starch than dogs or omnivores.   Cats can use carbohydrates as a source of metabolic energy, they have limited ability to spare protein utilisation by using carbohydrates instead. 

  • In spite of this, commercial diets are formulated with a mixture of animal and plant derived nutrients, most commonly in dry kibble form that requires carbohydrates for the expansion and cooking process.


  • Cats are metabolically adapted to preferentially use protein and fat as energy sources.

  • This evolutionary difference in energy metabolism mandates cats to use protein for maintenance of blood glucose concentrations even when sources of protein in the diet are limiting.

  • Adult cats require 2 to 3 times more protein in their diet than adults of omnivorous species.

  • Cats have an increased need for dispensable protein

    • Cat nutrition studies show that cats continue to use protein (eg, dispensable nitrogen in the form of gluconeogenic amino acids) for production of energy and in other metabolic pathways (eg. urea cycle), even in the face of low availability of proteins.


  • Cats also have a need for increased amounts of specific amino acids in their diet:  taurine, arginine, methionine, and cysteine.  Cats neither have the ability to synthesize these amino acids, nor are the amino acids conserved in their bodies. In fact, utilization of these amino acids (taurine, arginine, methionine, and cysteine) is higher in cats than in dogs or other animals.  It is likely that they have not developed mechanisms to conserve them due to the abundance available in their natural diet



  • Cats lack salivary amylase, the enzyme responsible for initiating carbohydrate digestion

  • Cats have low activities of intestinal and pancreatic amylase and reduced activities of intestinal disaccharides that break down carbohydrates in the small intestines.


  • Cats can use starch efficiently BUT as carnivores, high amounts of carbohydrates in the diet may have negative effects on their health


  • decrease protein digestibility in cats


  • cause a reduction in faecal pH in cats (due to incomplete carbohydrate fermentation in the small intestine that results in increased microbial fermentation in the colon and increased production of organic acids).


Hepatic function


  • The liver of the cat has several distinct features that influence disaccharide metabolism:

    • Cats have minimal function of hepatic glucokinase, and the activity is not adaptive (ie cannot be upregulated with the diet contains large amounts of carbohydrates)

    • Cats have minimal activity of hepatic glycogen synthetase (the enzyme responsible for converting glucose to glycogen for storage in the liver).

    • Cats have limited ability to rapidly minimise hyperglycaemia from a large dietary glucose load.

    • The liver in cats does not contain fructokinase, an enzyme necessary for metabolism of simple sugars.

    • Cats are not attracted to foods with a sweet taste.  Cats prefer foods flavoured with animal products (eg fats, meats).




  • Meat based diets supply essential fatty acids to cats, including linoleic, linolenic, arachidonic acid, and some eicosotrienoic acid. 

  • Unlike other animals, cats lack adequate hepatic alpha-6-desaturase activity and other hepatic desaturases, all of which are required for syntheiss of arachidonic acid and eicosapentaenote and docosahexaenoate.

  • Cats do not have the enzymatic machinery to synthesise derivatives of arachidonic acid.




The vitamin needs of cats are unique


  • Cats require increased amounts of dietary water soluble B vitamins  including thiamine, niacin, pyridoxine (B6) and cobalamin(B12). Pyridoxine is especially important as it is an essential co-factor in all transaminase reactions , which are constantly active in cats due to their reliance of protein for energy as well as building and synthetic functions.  Since most water soluble B vitamins are not stored, except cobalamin, which is stored in the liver, a continual dietary source is required.

  • Cats cannot convert beta-carotene to retinol, the active form of vitamin A, thus the biologically active form must be obtained from the diet – from animal tissue.

  • Cats lack the enzyme to allow dermal synthesis of Vitamin D. Vitamin D is found in high levels in fat and liver tissue – thus needs are normally met from the natural diet.




  • Cats have a less sensitive response to thirst and dehydration than dogs and other omnivores. This reflects their development as desert animals and as strict carnivores, which obtain most of their water requirements from their prey.

  • In older cats which produce urine with a lower SG, an increase in water consumption is very important to prevent dehydration and the development of a pre-renal azotaemia


The effect of diet on obesity in cats


  • Cats housed exclusively indoors and consuming energy-dense, high-starch, dry foods are provided with more energy than they can effectively use.  Any dietary carbohydrates not used for energy is converted and store as fats.

  • Diets that are severely restricted for energy (eg traditional low fat, high fibre, weight loss diets) may result in weight loss, but it is often to the detriment of lean body mass.

  • In a study by Nguyen et al. (2001), weight reduction in cats on a high protein, low carbohydrate diet was compared with that for cats fed a commercial hypoenergetic diet.  Cats in both groups lost weight, but cats consuming the high protein low carb diet maintained lean body mass during weight loss.

    • Nguyen P, Martin L, Siliart B et al 2001, Weight loss in obese cats: evaluation of a high protein diet’, in Proceedings.  Waltham International Symposium on Small Animal Nutrition, vol 28.


  • The effect of Diet on Hepatic Lipidosis 


  • The effect of Diet on Diabetes Mellitus


  • The effect of Diet on Inflammatory Bowel Disease

bottom of page