The correct nutritional support will help your horse perform at his best, yet an unbalanced diet could lead to a below-par performance and even a clinical problem.

The foundation of any horse’s diet (other than that of suckling foals) should be forage, such as fresh pasture, hay or haylage, of an appropriate nutritional and hygienic quality and in sufficient amounts. This is the starting point for getting the energy balance right.

Many horses don’t require any other energy-providing feed, just an appropriate balancer. Standard-bred trotters, for example, have been successfully raced on high nutritional-quality forage plus a balancer. Many performance horses are given energy-providing feeds in addition to, or as a substitute for part of this important forage element. Unless carefully managed, this can increase the risk of certain health problems.

Doing the maths

Different forage types contain different amounts of moisture. Silage is more than 50% water, whereas haylage is between 15% and 50% and hay between 5% and 15%. It’s therefore important to provide forage according to the dry matter (DM) content rather than on an “as fed” basis — especially when feeding haylage.

As an example, 13kg (as fed) of a 70% DM haylage is equivalent to 10kg (as fed) of a 90% DM hay. Both will provide your horse with 9kg of forage DM.

For gut health and general welfare, horses (other than those on a weight-loss programme) should ideally be fed forage ad lib, and at least 15gDM/kg bodyweight (i.e. 1.5% of bodyweight). This would mean giving a minimum of 7.5kg forage DM for a 500kg horse per day. This equates to 8.5kg of a 90% DM hay, or 11kg of a 70% DM haylage.

Even those horses in very high intensity work should be fed forage amounting to at least 12.5g DM/kg bodyweight (i.e. 1.25% of bodyweight).

Quality counts

Many hays and haylages, fed alone, do not provide sufficient vitamins, minerals and trace elements. Nor do they routinely supply good-quality amino acids and protein to meet optimal requirements, especially grass-based forages and particularly if soaked before feeding. An appropriate balancer is therefore needed.

Forage analysis is helpful to estimate energy content. As grass matures, typically fibre increases and energy content decreases. This means that horses with very high energy requirements will usually benefit from less mature forage.

Horses prone to conditions such as polysaccharide storage myopathy (PSSM) or laminitis should be fed low-sugar, low-starch forage — ideally less than 12% on a DM basis. Soaking helps reduce sugar content, but by a variable amount. Ideally, start with forage with a known low content, or analyse post-soaking.

Very mature, highly lignified hays and long straw should provide, as a maximum, only a small percentage of the long fibre ration, and must be introduced gradually to help lower the risk of certain types of colic.

The hygienic quality of forage is key, especially for gut and respiratory health. Overtly dusty and mouldy hay, which obviously should not be fed, can be identified simply by looking at it, feeling it and smelling it, but there may not be obvious signs that hay is of poor hygienic quality. If you are concerned, get it analysed and consider practices such as steaming (although this will not resolve all hygiene issues). Be vigilant for contamination by way of toxic plants or foreign bodies, and store all feed and forage appropriately.

Consider, too, your horse’s feeding schedule. Long periods of time spent without forage will increase the risk of certain types of gastric ulcer and behavioural issues, so ideally feed forage ad lib. If intake needs to be restricted, divide the overall amount into several meals per day and try to extend the time the horse
spends foraging.

Changing forage or feed can also help trigger certain types of colic. Small changes should be made gradually, over three to five days, while any major changes may require a two- to three-week adaptation period.

pony nuts, horse feed

Energy boost

Some performance horses require more energy than ad-lib forage can provide. In these cases, fibre-based options include feeding less mature forage, which provides more energy, and/or adding highly digestible fibre sources. These could be in the form of soaked, unmolassed sugar beet, or a commercially prepared, nutritionally balanced feed with a high-fibre content and low or restricted levels of starch.

• Non-rancid vegetable oil or fat has high energy density and lacks starch content, but it must be fed consistently for several months for the horse to gain any possible additional metabolic benefits.
Introduce oil or fat to the diet gradually, over several days or weeks, depending on the volume being added. Up to 1ml of oil or fat per kg of bodyweight can be fed per day, but obtain nutritional advice if you plan to exceed these levels. Check the balance of vitamins (especially vitamin E) and minerals in the resulting diet, or choose a balanced high-oil, high-fibre feed as an alternative.

• Starch in cereal grains can provide energy, but exceeding the limited tolerance for starch ingestion can lead to problems.
Cereals contain different amounts of starch — oats contain around 40% as fed, barley around 50% and maize around 60% — and are not nutritionally balanced. Some sources of starch are less digestible in the small intestine, although heat processing can improve digestibility. Grains, other than oats, in compound or complementary feeds should always be cooked (flaked or micronised, for example).

• Several studies recommend a safe upper limit for starch and sugar intake: around 2g per kg of bodyweight per day, from the non-forage feed portion, with a maximum of 1g per kg of bodyweight per meal. Any more poses a potential greater health risk.
Where necessary, increase the number of meals, offering no more than 0.4kg of feed per 100kg of bodyweight at a time. This amounts to less than 2kg per meal for a 500kg horse.

Potential risks

Fermentation of excess sugar and starch by the stomach microorganisms leads to a more reduced pH and increased production of volatile fatty acids.

In combination, these can damage certain parts of the stomach wall and make gastric ulcers more likely. Sugar and starch not digested and absorbed in the small intestine will enter the hindgut, resulting in an altered environment, which is sub-optimal for fibre-digesting bacteria. Changes in the microfloral population, plus a decrease in pH, increases the risk of diarrhoea, colic and laminitis.

Energy in the mix

Coarse mixes are typically based on grains, sources of fibre, fat or oil as well as protein — plus some vitamins and minerals. Sugar and starch levels depend on which ingredients are being used and at what level.

horse mix
These products can provide as much energy as pure barley, but with restricted (less than 25%) or low starch (e.g. less than 10%, if they’re based primarily on highly digestible fibre sources, plus oil with almost no grain). If you cannot find levels on the feed bag label or company website, ask the manufacturer.

Too much sugar and starch?

A 500kg performance horse is fed 2kg of flaked barley and 2kg of a complementary feed (25% starch and 10% sugar), plus 8.5kg (as fed) of mature hay per day. The feed is divided into two meals.

• Barley: 2,000g x 0.5 (50% starch) = 1,000g starch
• Feed mix: 2,000g x 0.25 (25% starch) = 500g starch
• 2,000g x 0.1 (10% sugar) = 200g sugar
Total: 1,700g

When divided by the weight of the horse, this gives 3.4g of sugar and starch per kg of bodyweight per day. This is significantly more than the recommended daily intake (and, at 1.7g/kg bodyweight per meal, is more than the recommended per meal intake). These levels raise the likelihood of various health problems.

Forage can also contain high amounts of sugar, often more than 15% DM. It’s an important factor to take into account if the horse has certain metabolic problems or a predisposition to laminitis.

Ref Horse & Hound; 1 September 2016