Keeping a step ahead of GastroIntestinal conditions


As practitioners, we realise that appropriate nutrition for gastrointestinal disease is part of the mainstay of treatment, but which diet should you choose from the plethora of options?

This is a really common question and whilst every patient is different here are some general guidelines to help you choose what to try first.

There are four main types of gastrointestinal diets:

  • Highly digestible (eg Hill’s Prescription Diet i/d)
  • Increased fibre (eg Hill’s Prescription Diet Gastrointestinal Biome, Hill’s Prescription Diet w/d)
  • Low fat (Hill’s Prescription Diet i/d Low Fat)
  • Low allergen
    • Novel ingredients (eg Hills Prescription Diet d/d)
    • Hydrolysed protein (eg Hill’s Prescription Diet z/d)

The first question you need to ask yourself is:

Is the diarrhoea small bowel or large bowel?

It can be a bit of trial and error to determine the best diet for a particular patient; however this will help guide you with choosing an initial dietary option. Here is a handy table to help you ascertain whether it is small or large bowel. Some patients will have a mix of both small and large bowel, in which case you will need to experiment to determine the best diet.

Clinical signs of large bowel diarrhoea versus small bowel diarrhoea*

Small IntestineLarge Intestine
Large volume of faecesSmall volume of faeces
Normal or mild increase in frequency of defecation (3-5 times per day)Significantly increased frequency of defecation (>5 times per day)
No urgencyUrgency
Fat in faecesFat is absent
Digested blood (black in colour)Frank blood (red in colour)
Mucus usually absentMucus in faeces
Vomiting frequentVomiting rare
Weight lossWeight loss rare
Loose, watery stoolSoft to semi formed stools

*Small Animal Clinical Nutrition 5th Edition. ©2020 Hill’s Pet Nutrition Pty Limited.

The next question to ask is what diet has been previously tried (if any) and was the owner compliant 100% of the time?

Small bowel disorders

You may wish to choose a nutritional option which is low fat (dog), highly digestible, or a novel/hydrolysed protein, depending on the condition.

  • Acute enteritis and gastroenteritis

Typically, start with a highly digestible diet unless underlying food allergy or pancreatitis is suspected.1 These patients may require small, frequent meals. 

For acute diarrhoea, dietary indiscretions or recovery from surgery,  we tend to recommend Prescription Diet i/d. It is low residue which means that it is highly digestible, has prebiotic fibres to nourish the pets’ microbiome, and contains high levels of B complex vitamins and electrolytes to help replace any losses through vomiting and diarrhoea. It is also safe to use in puppies and kittens.

Rather than withholding food we now recommend early feeding. There are multiple benefits in this,  including improved recovery time, decreased bacterial translocation and sepsis, and avoiding mucosal atrophy.2  

  • Food Responsive Enteropathy or Inflammatory Bowel Disease

In these conditions there is a loss of tolerance to dietary antigens so we want to avoid excessive protein and choose a diet which has a novel protein (e.g. Hill’s d/d) or hydrolysed protein (e.g. Hills z/d). Hill’s d/d contains venison as the protein source whilst Hill’s z/d contains a hydrolysed chicken liver.

For fibre responsive enteropathies the gastrointestinal biome diet makes an excellent choice.

  • Acute pancreatitis, exocrine pancreatitic insufficiency or lymphangiectasia

For dogs we typically want to feed something that is low in fat and highly digestible, so Hill’s i/d Low Fat makes a great option here, with a fat content of 7.7% on a dry matter basis in the dry formulation.4,5 Hill’s i/d Low Fat also has the prebiotic fibres beet pulp and flaxseed. 

Large Intestinal Disorders

Patients with primarily large bowel signs may respond better to a higher fibre diet.6 Other options are the novel or hydrolysed protein or highly digestible diets.

Fibres can be classified depending on their solubility and their fermentability.

Soluble fibres dissolve in water and have a gelling effect and tend to delay gastric emptying and slow transit time.

Insoluble fibres do not dissolve in water and some can provide a bulking effect by absorbing water as they move through the digestive system. This can assist the movement of food through the gastrointestinal tract by stimulating peristalsis.

Fermentable fibres have a pre-biotic effect, so feed the beneficial bacteria and the bacteria in turn produce short chain fatty acids such as butyrate which acts as an energy source for the colonocytes. 


The Gastrointestinal Biome diet is an excellent choice for patients with colitis, as well as patients with antibiotic responsive diarrhoea, or patients with suspected dysbiosis. The ActiveBiome+ Ingredient technology which is a proprietary blend of prebiotics has been shown to rapidly activate the microbiome to support digestive health and well-being.  Hill’s Gastrointestinal Biome has demonstrated clinical results in cats with constipation or diarrhoea7 and dogs with diarrhoea8 in as little as 24 hours. This diet contains both soluble and insoluble fibres.

Hill’s w/d contains a higher amount of insoluble fibre so is useful in cases where bulking to the stool is required. Please see the table below for further indications.

Length of food trial

When doing a food trial for patients with gastrointestinal signs they typically should respond within 2-4 weeks, so if you are not seeing results within that period you can try something else.9

If you have a complicated case that you would like a bit of advice on then please contact our Hill’s Helpline on 1800 679 932.


  1. Cave N. Dietary Approach to Gastrointestinal Disorders. In: Acute Gastroenteritis. Proceedings of the 2010 World Small Animal Veterinary Association Congress
  2. Mohr AJ, Leisewitz AL, Jacobson LS, et al. Effect of early enteral nutrition on intestinal permeability, intestinal protein loss, and outcome in dogs with severe parvoviral enteritis. J Vet Intern Med 2003;17:791-798
  3. Davenport DJ, Jergens AE, Remillard RL. Inflammatory Bowel Disease. In Hand, MS, Thatcher CD, Remillard RL et al (eds). Small Animal Clinical Nutrition, 5th Edition,2010: 1069
  4. Hill’s Pet Nutrition, Data on File, 2012
  5. Davenport DJ, Remillard RJ, Simpson KW, Acute & Chronic Pancreatitis in Small Animal Clinical Nutrition, 5th Edition, 67: 1147
  6. Davenport DJ, Remillard RL, Carroll M. Large Bowel Diarrhoea: Colitis. In: Hand MS, Thatcher CD, Remillard RL et al (eds). Small Animal Clinical Nutrition, 5th Edition, 2010: 1103-1104
  7. Wernimont, S.M., et al. Food with Specialized Dietary Fiber Sources Improves Clinical Outcomes in Adult Cats with Constipation or Diarrhea (in a 2 Month Study). FASEB J. 2020;34(1). Some cats may require multimodal management
  8. Fritsch, D.A., et al. Food with Novel Fiber Blend Improves Clinical Outcomes and Changes  Gastrointestinal Microbiome Metabolism in Dogs (in a 2 Month Study). J Vet Intern Med. 2019;33(5):2513
  9. Roudebush P, Guilford WG, Shanley KJ, Adverse Reaction to Food. In . In Hand, MS, Thatcher CD, Remillard RL et al (eds). Small Animal Clinical Nutrition 4th Edition. 31:625 

Dr Bryony Senic, BSc,BVMS

Bryony graduated in 2007 from Murdoch University in Perth. She worked as a veterinarian in small animal practice treating primarily dogs and cats for almost 7 years before moving to an industry role with Hill’s Pet Nutrition in 2015. She works as a Professional Development Veterinarian for South Australia and Western Australia and is passionate about nutrition in pets.


Please enter your comment!
Please enter your name here