by Dr Derek Cuddeford, Royal (Dick) School of Veterinary Studies, University of Edinburgh
Animals that undergo surgery cannot usually eat normally for a period of time and may temporarily starve. The extent of time that the animal is without food or that it under eats depends on the seriousness of the intervention and which body systems are compromised. Clearly, abdominal surgery that involves the gastrointestinal tract will have a greater impact on the nutritional status of the animal than arthroscopy of a knee joint. Horses that fail to rapidly regain nutritional competence after surgery are susceptible to increasing malnutrition in a situation where the body is already in a stressed postsurgical state. Postoperative fluid and electrolyte management may be required although large volumes are usually necessary. This can be adequate for meeting minimal short-term nutritional requirements postoperatively. If a return to oral intake is delayed essentially the animal will starve unless other means can be found to support the animal’s metabolism. Obviously a horse with compromised nutritional status is more at risk from morbidity and mortality.
When energy and nutrient intake falls below that necessary for maintenance then the animal becomes catabolic. This means it starts breaking down body tissues to make good the shortfall in energy and nutrient supplies. The body “eats” itself. Anyone who has had a relative or themselves in hospital for major surgery will have witnessed firsthand how quickly “condition” is lost in spite of what appears to be adequate food inputs furthermore, nobody gets fat on grapes or flowers! Bodily fat starts to disappear and then this is soon followed by protein breakdown. Unfortunately protein is not stored in the body like fat so essential tissue is lost and in serious cases of starvation, muscle wastage occurs and organ tissue is lost that can ultimately lead to organ failure. In most cases following surgery, “starvation” is a very short term issue because re-alimentation can begin quite quickly in contrast to the starved horse which has undergone chronic underfeeding and can be in a bad way.
The guide to feeding post-surgery is relatively straightforward. Oral surgery such as removal of teeth etc can compromise the animal’s ability to ingest and masticate food. These changes may be temporary or permanent. The simplest approach is to rehydrate good quality grass pellets. The extent of rehydration will govern the form of the final product which can range from a soft “fluffy” mix to a green slurry that the horse can slurp up. This type of food is also good after abdominal surgery as it will “flow” easily through the digestive tract. Remember, the horse is used to consuming wet food since grass can contain up to 87% water just like milk. Nothing is better for the horse than grass! If parts of the gut have been removed then those parts remaining will dictate what is fed. Instead of the horse having two distinctive areas that you can feed, the small intestine for hydrolysable carbohydrates, proteins and fats and the large intestine for fibrous feeds, the horse may be left with much reduced capability in one of these regions.
There are no dietary changes required for a horse having undergone surgery in which no part of the small intestine or less than 50% of the jejunum and/or duodenum or the caecum is removed. Horses recovering from surgery generally should, as a rule, be fed high-quality, highly digestible feeds in small, frequent meals as soon as they are back on their legs. Offer the horse about one-quarter of its normal ration, increasing to its maintenance ration over several days. Fresh water should always be available and those horses that have “lost” some of their large intestine will have a higher requirement since water re-absorption is compromised. You can walk the horse in hand and allow it to graze fresh grass for short periods.
Following removal of part of the large intestine, horses are usually fasted for up to 24 hours in order to aid healing and to preventing over stretching of the gut. However, not feeding for more than 72 hours can result in less effective wound healing and an increased risk of infection and diarrhoea. Thus, it is necessary to reintroduce solid feed to prevent gut tissue from becoming damaged. Horses can eat small amounts of high-quality feeds (alfalfa or alfalfa/grass mixes) over the first month after surgery. Extra protein (12% or more) and phosphorus (0.4% minimum) should be fed together with limited amounts of structural fibre (< 28%) because the animal is less able to digest and absorb nutrients after surgery. If large sections of the colon have been removed such horses may need to remain on an altered feeding programme for the rest of their lives. Horses in which only small parts of the left colon and/or caecum have been taken out usually regain the ability to absorb nutrients and can revert to normal maintenance feeding.
Removal of parts of the small intestine means that cereal or starch-rich feed should not be fed. High quality fibre feeds and those containing a lot of fermentable fibre can be used whether as straights (beet pulp) or in compounds. Significant supplementation may be necessary to compensate the impaired digestion of starch, fat and protein and the reduced absorption of vitamins and minerals. The large intestine can, to some extent, make up for the loss of small intestinal functionality.
In contrast to the foregoing, the chronically underfed horse can be either mildly malnourished or seriously catabolic. The first thing to do with an apparently starved horse is to have it undergo a full veterinary exam. Obviously teeth must be OK, the animal must be free from parasites and not suffering from any medical condition before you start re-alimentation. Avoid the temptation to give lots of goodies as you may kill the horse! Nutritional rehabilitation is a slow process and is best achieved by providing increasing amounts of good quality forage. Alfalfa hay has been shown to be the best material to use providing protein, little starch and essential minerals. The addition of oil does not provoke an undesirable insulin response but effectively it dilutes the protein and mineral supply. For the first 3 days of re-feeding a horse that should weigh 500kg should be fed between 500 and 700g alfalfa every 4 hours. On days 4 to 5 feed 1kg alfalfa every 4 hours providing the horse remains well and does not become diarrhoeic. Gradually increase the amounts of alfalfa fed at each meal to 2kg and aim to decrease the meal frequency to once every 8 hours by day 10. Continue increasing the amounts until the animal is eating ad libitum by day 14. Should alfalfa feeding prove unsuitable because of diarrhoea, substitute grass or grass hay. Avoid the temptation to introduce concentrate too early, preferably waiting until 4 weeks are up and then start with handfuls and not bucketfuls! A 12% protein concentrate introduced very slowly would be alright but not exceeding 1% of liveweight. There are some high oil/high fibre/low starch concentrates available for purchase and these are very good for rehabilitating horses. Feed refusal can be a problem so only the freshest cleanest material should be offered. Fresh grass will often be consumed if all else fails. Succulents and bran mashes may help to tempt the horse to eat.
In conclusion, in both cases of feeding following surgery or of rehabilitation of a starved animal, the great temptation to feed cereals/concentrates in quantity should be ignored. Based on investigations to date the key ingredient in both recovery situations is high quality forage.