What do horses eat? Hay, grazing and when to add feed

Hay and grazing: the foundation of the diet

Defra's code of practice on horse welfare describes horses as natural grazers that eat little and often, mainly on fibre-rich grass. Outside working hours they should have almost constant access to forage: grass, hay or haylage. The British Horse Society (BHS) agrees that forage should form the basis of any horse's diet. Croatian researchers from the Zagreb faculties of agriculture and veterinary medicine (Kostelić, Prvanović Babić and Džakula) warn that some breeders believe poor hay can be made up for with concentrates, when good hay and pasture are the foundation and cereals only an addition.

Sources differ on how long a horse would spend eating in the wild: Defra says 16 to 20 hours a day, World Horse Welfare 16 to 18, the BHS up to 18, and an adviser at the Slovenian extension service KGZS (Novo mesto) 12 to 16. All point the same way: the gut is built for near-continuous chewing. Chewing produces saliva, which buffers the stomach acid horses secrete all the time, so long gaps without forage are linked to gastric ulcers (BHS, KGZS); enough forage also helps reduce the risk of colic (BHS).

Forage first; concentrate, supplements and amounts follow from work, condition and professional advice.

How much forage a day

Sources quote rough percentages of body weight per day. These are guidelines for most adult horses, not rules, and they differ partly because they count different things:

None of these figures is a recipe for every horse. Defra says a ration should reflect the individual's age, type, weight, condition, health and workload, and the University of Minnesota encourages working with an equine nutritionist. Most sources here are British or American, so check amounts with a vet or nutritionist.

Quality matters as much as quantity. Defra describes good conserved forage as clean (free from soil, debris and poisonous plants), fresh-smelling and visibly free from mould and dust. Haylage is cut earlier than hay, only partly dried and wrapped in plastic, so it is more nutritious and wetter and needs using fairly quickly once opened (BHS). Nutrient content varies between batches, and the BHS mentions sending a sample to a feed company for analysis.

How much a horse eats at grass is hard to estimate. Studies cited by the BHS found that ponies with 24-hour access to pasture can eat up to 5% of their body weight, and up to 1% in just three hours, so for some horses grazing is a risk as well as a food source.

Water

Water has to be available all the time. Defra says an average-sized adult horse can drink 25 to 50 litres a day (roughly 5 to 10 litres per 100 kg); Merck gives an average minimum of 5 litres per 100 kg for a resting adult in mild conditions. Needs rise in hot weather and after exercise, and a horse fed only dry hay may drink almost twice as much as one on mixed feed or grass, because fresh grass contains more water (Merck).

Too little water reduces feed intake and raises the incidence of impaction colic (Merck); the BHS adds that food passes along the gut less easily when the supply has frozen. Defra therefore advises breaking ice regularly in winter, an extra source in hot weather, and regular cleaning of troughs.

Salt and minerals

Salt (sodium chloride) should be on offer free choice, as a block or loose, and the horse regulates its own intake (University of Minnesota). Merck recommends this because forage contains no notable sodium and most commercial concentrates do not provide enough. Consumption varies widely (Merck cites one study ranging from 19 to 134 g a day) and rises with sweating.

On vitamins and minerals, sources disagree. Penn State Extension says a healthy horse on good forage plus a commercial feed is most likely well supplied with minerals, and the University of Minnesota says the same of a commercial grain feed given as the manufacturer directs. World Horse Welfare, on a page compiled with its partner, the feed manufacturer Baileys Horse Feeds, says modern pasture and forage are often short of some vitamins and minerals and recommends a supplementary feed even for horses that hold condition on grazing and hay alone. The BHS calls balancers (concentrated vitamin and mineral feeds) useful when a horse needs no extra energy but does need the nutrients.

So there is no universal answer. Forage analysis and a talk with a vet or nutritionist help: the BHS advises taking advice before feeding supplements, and Merck warns that selenium has a very narrow margin of safety and that mineral intake should be judged from all sources, including water.

Concentrates: when and for whom

Concentrates are starch-rich, energy-dense feeds such as oats, barley and maize. The BHS says they are often needed only by horses in medium to hard work, those that need to gain weight and those that struggle to hold condition; most leisure horses can keep a healthy weight on a high-forage diet. World Horse Welfare adds that many need only a vitamin and mineral supplement or balancer.

Defra says concentrate should be no more than is needed for the energy of the work done or for any required weight gain, since too much can contribute to obesity, digestive upset and laminitis, a debilitating disease that, Defra notes, can affect any horse and any or all of its feet. A daily concentrate ration should be spread over at least two meals. The Zagreb authors add that large amounts of energy-rich concentrate can cause colic and laminitis, and that finely ground grain ferments very quickly in the gut.

Feeding routine and gradual changes

Change feed slowly. Defra warns that sudden changes in quantity, type of feed or hay can cause digestive upset, including colic and diarrhoea. Merck and the BHS talk of roughly 10 to 14 days. The reason is the bacteria in the large intestine, which need time to adapt to new feed (World Horse Welfare, KGZS). When to call a vet about colic is covered in colic in horses.

Body condition and weight: how to keep track

Defra advises monitoring every horse's weight and condition regularly, since obesity is as serious a concern as being underweight. World Horse Welfare says you cannot reliably tell by eye how much fat a horse carries, so hands-on checking is needed: the BHS scores the neck, middle and hindquarters, where fat feels spongy and muscle firmer.

Both scales exist (World Horse Welfare), so do not mix the numbers up: 3 is healthy on the 0–5 scale but below the 4–6 quoted by the University of Minnesota and Merck on the 1–9 scale. Horses in hard work can look underweight while being fit, with well-developed muscle (BHS).

To track weight, the BHS and World Horse Welfare suggest fat scoring and weigh taping every two weeks. Merck cautions that weigh tapes tend to underestimate weight and are the least accurate tool, though useful for following change, and are not suitable for miniature horses, donkeys or draught horses. Note the date, score and girth measurement to see the trend that the eye misses.

Special cases

Horses that gain weight easily

The BHS says that, compared with Thoroughbreds, draught types, cobs and native breeds are more likely to be overweight, because they evolved to survive on poor grazing; Shetland ponies are its prime example, and the profiles of the Shetland pony and the Haflinger describe something similar. Excessive weight gain more than doubles the risk of laminitis (BHS). Defra adds that obesity and over-eating remain major factors, that eating excess lush grass or concentrate may also be associated with it, and that it can occur in horses that are not overweight. Long-term excess weight may also lead to hormonal disease such as equine metabolic syndrome (EMS), which can predispose horses to laminitis; once a horse has had laminitis it tends to be at increased risk of it recurring. Defra says such horses need close attention to management and diet, and any concern should go to your vet.

Sources describe control without starving the horse: strip grazing with electric fencing, a track system, a grazing muzzle and lower-calorie hay (BHS, Defra). World Horse Welfare advises against crash diets because horses need a steady supply of food, and Merck warns that prolonged restriction can cause hyperlipaemia, especially in ponies, donkeys and severely obese horses. Agree any weight-loss plan with your vet. World Horse Welfare also suggests more walking for overweight horses, since a brisk walk or steady trot burns more fat than faster work; see how much exercise a horse needs.

Older horses

A healthy older horse in ideal condition has needs similar to a younger adult's (BHS); problems start when health declines. Worn teeth make chewing harder and raise the risk of colic, choke and weight loss. The BHS recommends soaked, softer feed as a fibre replacement, the ration split into four or five small feeds, and, for older horses, a dental check every 6 to 12 months. See horse teeth for more.

Working and competition horses

More work needs more energy. World Horse Welfare advises swapping low-calorie forage for higher-calorie forage first and only then replacing some forage with concentrate; the BHS asks for an honest assessment of the work, since too much high-energy feed leads to behaviour problems, gastric ulcers and obesity. Defra says a horse should not have concentrate or a large forage meal immediately before or after strenuous exercise, while a small handful of forage beforehand may reduce the risk of ulcers.

Kostelić and colleagues give paralytic myoglobinuria, popularly called “praznička bolest”, as their best example of how cereal feeding can harm a horse's health. It regularly appeared in working horses given large amounts of oats or, more often, maize during work and the same ration at rest; back in harness, their muscles stiffened. The authors say the disease is often seen in cold-blooded horses and not infrequently in sport horses too, and that the amount of energy feed must be adjusted to the horse's purpose and workload.

Treats

The BHS counts apples, carrots, swede and parsnips among safe succulent treats. They add variety but also calories, so feed them in moderation to overweight horses or those prone to laminitis, sliced lengthways, never into rounds or cubes, to reduce the risk of choke. World Horse Welfare says treats should be the exception, not the rule. What must stay out of the bucket altogether is covered in what horses must not eat.

When to seek professional advice

Not every vet works with horses: when you search the Vets directory, check that the practice sees horses. A general overview of care is in how to care for a horse.

How much hay does a horse eat a day?

It depends on the horse's weight, workload and the quality of the hay or grass. As a guideline the sources give roughly 1.5 to 2.5% of body weight a day (BHS 2 to 2.5%, at least 1.5%; Merck at least 1.5 to 2%; University of Minnesota 1.5 to 2.5%), though some count all feed and others only forage. Check the amount for your own horse with a vet.

Does a horse need oats or other concentrate feed?

Often not. According to the BHS, most leisure horses not in hard work hold a healthy weight on a hay- and grass-based diet, while oats and other cereals come into play for harder work or when a horse struggles to keep condition. If only vitamins and minerals are lacking, balancers add little energy.

How often should a horse be fed?

Spread meals through the day, because the horse's gut is built for frequent small amounts. KGZS recommends at least three meals with no overly long overnight gap, and Defra says any concentrate ration should be split into at least two. Keep feeding times similar from day to day.

Does a horse need a salt lick?

Yes, salt should be on offer for the horse to help itself: Merck and the University of Minnesota recommend a block or loose salt on free choice. Forage contains little sodium, and needs differ between horses and rise with sweating, so no amount is prescribed and the horse regulates its own intake.

How much water does a horse drink?

Defra gives roughly 25 to 50 litres a day for an average-sized adult, but it depends on the horse and conditions. A horse drinks more in hot weather, after exercise and on dry hay. More important than the number is that clean water is always within reach and does not freeze in winter.

What do horses eat in winter?

In winter, hay or haylage is the mainstay, because grass is scarce (BHS). Two things need care: water must not freeze, since that may raise the risk of colic, and older horses become less effective at keeping warm, so one that loses weight over winter needs shelter, rugs and extra feed (BHS).