How to: provide assisted enteral nutrition

Research output: Book chapter/Published conference paperConference paper



In humans, malnutrition is associated with increased morbidity, increased risk of infection and prolonged hospitalisation, and early nutritional support of patients is commonplace. Although the effect of nutritional deficits in horses is less well understood, nutritional support is likely to be of benefit. Methods for nutritional support include provision of feedstuffs to horses willing and able to eat, assisted enteral nutrition (AEN) and parenteral nutrition (PN). In human medicine, while uncertainty remains as to whether AEN or PN provides superior clinical outcomes (Gramlich et al. 2004; Simpson and Doig 2005), early AEN has been associated with reduced patient morbidity and mortality. Data for direct comparison of AEN versus PN in horses is not available to facilitate clinical decision making. However, AEN is cheaper, easier to administer, associated with fewer side effects, and likely supports physiological mechanisms (e.g. gastro-intestinal function) and immunity. Enteral nutrition is associated with support of organ blood flow and function, maintenance of body condition, trophic stimulation of GIT mucosa and preservation of the barrier function of the GIT mucosa to invasion of pathogenic micro-organisms (Carr and Holcombe 2009). As such, in the patient that can tolerate enteral nutrition, this route is an intuitive selection for nutritional support in horses.

Which patients require AEN?

Any animal with or at the risk of malnutrition is a candidate for AEN, provided integrity of the GIT is present. Those animals with ileus, recumbency, inability to maintain normal head position or obstructive conditions of the GIT require PN. Animals that are most likely to benefit from AEN include those undergoing post-operative management (including GIT surgical cases) and those with enterocolitis, dysphagia, oral/neck trauma, cachexia, obesity, systemic illness or burns. In addition, AEN may be warranted in patients with underlying metabolic disease (e.g. insulin resistance), increased metabolic rate (e.g. foals) and/or increased nutritional requirements (e.g. trauma, sepsis). Consideration of body condition is important when managing a hypophagic/inappetant animal: those with minimal body energy reserves are at great risk of malnutrition. Obese animals, particularly those predisposed to insulin resistance (pony/miniature breeds, donkeys) are at risk of dyslipidaemias with inadequate feed intake and similarly require early nutritional intervention.

Nutritional requirements

Determining the nutritional requirements of an individual animal is difficult due to the varying influences of factors such as age, breed, body condition, animal fitness, neuroendocrine responses, surgery, trauma and inflammatory mediators. The caloric and protein requirements of horses with systemic disease, trauma, burns or following surgery have not been determined. Increased metabolic demands for many systemic conditions may be balanced by patient inactivity during hospitalisation (Carr and Holcombe 2009). Further, rapid or excessive alimentation may be associated with complications, including metabolic and electrolyte disturbances. As such, restrictive nutritional intake with the target of providing resting digestible energy requirements (DE [MCal/day] = BW x 0.021 + 0.975) is often appropriate. Exceptions may be marked trauma/tissue necrosis, severe burns and intestinal resection (Carr and Holcombe 2009). In addition provision of adequate protein is important to minimise protein catabolism. As a minimum, 40 grams of protein per MCal of maintenance DE is required (maintenance DE [MCal/day] = BW x 0.03 + 1.4).

Enteral nutrition formulation

Assisted enteral nutrition options include liquid formulations available for humans, commercial equine pelleted feeds and homemade equine enteral recipes. Liquid formulations have advantages of known nutritional content and ease of administration. However, because the formulations do not have fibre, animals may develop diarrhoea. Also, protein concentration is insufficient for daily requirements and casein supplementation may be necessary. High glucose or lipid concentrations in these preparations may increase the risk of abnormalities in patients with altered insulin/glucose or lipid metabolism.

Commercially-available complete pelleted feeds contain all the essential nutritional requirements for adult horses and are a good option for AEN after soaking in water and blending. The contained dietary fibre in these diets support large intestinal health and function, however the increased density necessitates administration through a large bore tube and careful tube management.

An equine AEN recipe formulated with dextrose, alfalfa meal, casein, electrolytes and minerals has been published (Naylor et al. 1984), and contains similar nutritional profile to complete pelleted feeds.

Methods for provision of AEN

The method of administration will depend on the formulation used, animal temperament, required volumes and the nutritional requirements of the animal. Irrespective of method used, rapid re-feeding should be avoided and horses should be commenced on 25-50% of the target daily volume for the first 1-2 days, increasing to 100% by day 3-4. With bolus dosing, the calculated amount/day should be divided into ≥ 2 feeds with a maximum volume/feed of 6-7 L for a 500kg horse. In a hospital setting, an indwelling large bore tube can be maintained. Diets with fibre content may require use of a stomach pump to ensure passage through the tube. Prior to each feed, the horse should be assessed to ensure no spontaneous reflux is present. A small bore (16-20F) indwelling tube can be placed for administration of liquid preparations, either as a bolus or continuous ‘trickle’ administration.


Parameters to monitor include bodyweight, faecal consistency and output, blood glucose, total protein, electrolytes, liver enzymes and triglycerides. If necessary, change in enteral preparation and/or electrolyte supplementation may be undertaken.


Carr, E.A. and Holcombe, S.J. (2009) Nutrition of critically ill horses. Vet. Clin. Equine 25, 93-108.

Gramlich, L., Kichian, K., Pinilla, J., Rodych, N.J., Dhaliwal, R. and Heyland, D.K. (2004) Does Enteral Nutrition Compared to Parenteral Nutrition Result in Better Outcomes in Critically Ill Adult Patients? A Systematic Review of the Literature. Nutrition 20, 843– 848.

Naylor, J.M., Freeman, D.E. and Kronfeld, D.S. (1984) Alimentation of hypophagic horses. Comp. Cont. Educ. Pract. Vet. 6, S93-99.

Simpson, F. And Doig, G.S. (2005) Parenteral vs. enteral nutrition in the critically ill patient: a meta-analysis of trials using the intention to treat principle. Intensive Care Med. 31,12–23.

Original languageEnglish
Title of host publicationHandbook of Presentations
Subtitle of host publicationBritish Equine Veterinary Association Congress 2013
PublisherBritish Equine Veterinary Association (BEVA)
Number of pages1
Publication statusPublished - 2013
Event52nd British Equine Veterinary Association Congress - Manchester, United Kingdom
Duration: 11 Sep 201314 Sep 2013


Conference52nd British Equine Veterinary Association Congress
Country/TerritoryUnited Kingdom


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