Dr. Tania Sundra

23 August 2018

What Should I Feed My Horse ?

I get to wander into a number of feed rooms as a veterinarian. My observations tell me at least one universal trend exists – a lot of the feed rooms resemble the inside of a laboratory with supplement after supplement lined up on shelves. I can’t help myself and I usually ask the question “why are you feeding [this] or [that]?”. The answer is usually one of three things :

“My friend said her horse does really well on it”
“The person at the feedstore recommended it”
“I saw it on facebook and everyone is raving about how it’s the best thing ever, so I thought I’d try it”

Most people don’t want to hear this, but here it goes: You’re probably wasting your money and your horse doesn’t actually need the majority of these supplements.


Basic horse feeding isn’t rocket science. By following a few simple rules, you should be able to meet your horse’s nutritional requirements fairly easily.


1. Your horse requires 6 main classes of nutrients to survive : water, carbohydrates, protein, fats, vitamins and minerals.

2. Water is the most important requirement of your horse. On average a 500kg horse will drink between 30-50L of water per day. Your horse will require more water when temperature, humidity or activity increases. A lactating mare will also have a higher water requirement. A horse which does not consume enough water will usually fall victim to impaction colic.

3. The basis of any good diet should include good quality hay and pasture. Most horses will consume around 2% of their body weight in hay per day. For a 500kg horse this equates to 10kg. Ideally, horses should be provided with ad lib hay (as much hay as they want to eat). If your horse is overweight, you can feed a low sugar hay option such as rhodes grass hay or low-sugar meadow hay (provided it has been tested ARGT-free). Soaking hay for 30-60 minutes also leaches the soluble sugars out of hay, making it a better option for horses who are obese or those suffering from EMS or laminitis. Soaking hay for longer leads to an increase in microbial growth and we do not recommend soaking for longer than 1hr.

4. Proteins are necessary for growth, development, repair and maintenance of body tissues. Growing horses have a higher protein requirement than mature horses. Older horses may require higher protein levels, however their kidney and liver function should be assessed before dietary protein levels are increased. Not all proteins are created equal – some are higher quality than others. Proteins are made up of amino acids. There are 21 amino acids that are required by your horse for protein synthesis. Some amino acids can be made by tissues within the body, whereas others must be provided in diet. These amino acids are known as essential amino acids. You shouldn’t just be looking for the amount of protein in your horse’s diet, but also the quality of the protein. The quality is determined by the amount of essential amino acids it provides. Lysine, methionine and threonine are the most important amino acids that should be provided in your horse’s diet. Lysine is very important – if your horse’s diet does not contain sufficient amounts of lysine, they will have difficulty utilizing any of the other amino acids. High quality proteins include full fat soyabean meal (excellent source of lysine), lupins, sunflower seeds and canola meal. Roughage such as Lucerne also contain high quality proteins due to its high levels of lysine.


Lysine is very important – if your horse’s diet does not contain sufficient amounts of lysine, they will have difficulty utilizing any of the other amino acids.


5. Fat provides an excellent source of calories and it is easily digested by horses making it very useful in diets of horses with high energy demands. Common sources of fat that are fed to horses include vegetable oils such as canola, corn, and soyabean as well as rice bran oil. On a kg-for-kg comparison, fats supply 2.5 x as much energy as the equivalent weight of oats. This basically means that if you want to supply more energy to your horse’s diet without increasing their overall feed intake, supplementing with fat can be an effective way to accomplish that. Adding fat can also decrease the amount of grain in the diet, making it a safer way to supply calories in horses prone to gastric ulcers, laminitis, equine metabolic syndrome and tying-up.

6. Vitamins play a vital role in your horse’s normal metabolism.Vitamins can be divided into two groups : Fat soluble vitamins (A, D, E & K) & Water soluble vitamins (C & B-complex). In 2007, the National Research Council (NRC) published the Nutrient Requirement of Horses which estimates the daily requirements of vitamins A, D, E, and the B vitamins (thiamin & riboflavin). Vitamin A & E are present in high concentrations in fresh green feed or new-season grass hay. A horse predominantly grazing pasture will generally meet its Vitamin A & E requirements. Horses do not make Vitamin E and they require daily supplementation if green feed is not available (ie. during summer). Horses which have limited access to pasture (eg. due to laminitis, EMS or re-hab from injury) should be fed a balanced vitamin and mineral supplement to account for this shortfall. Vitamin D requirements of horses can be met if the horse is exposed to sunlight for at least 4-6hrs per day. The ultraviolet rays from the sun will convert a compound found in the skin (7-dehydrocholesterol) to Vitamin D. Hay which has been allowed to cure in the sun also contains high levels of vitamin D. Sufficient levels of vitamin D must be present in the body for calcium and phosphorous to be absorbed. Vitamin D deficiency reduces the absorption of both minerals. This is particularly important in young, growing horses.


Horses do not make Vitamin E and they require daily supplementation if green feed is not available


7. The mineral requirements of your horse will vary based on its body weight, age, condition and activity levels. The essential major minerals your horse requires are calcium, phosphorous, magnesium, sodium, chloride, potassium and sulphur. Essential trace minerals are iron, zinc, copper, selenium, manganese, iodine and cobalt. Getting the balance of minerals correct is very important – less than the recommended quantities can result in a dietary deficiency, whereas providing these in excess quantities can result in toxicity.The calcium to phosphorous ratio is a particularly important aspect of mineral nutrition in the horse. The Ca:P ratio should be 2:1. An incorrect ratio can result in bone disorders in young, growing horses. The Ca and P ratio of hay and grain can be quite variable. Grains are typically higher in P and low in Ca. Magnesium, potassium and sulphur are typically adequate in forage. The sodium and chloride requirements can be met by supplementing with salt, however a horse in heavy work that sweats a lot may require supplementation with potassium, sodium and chloride to replace the minerals lost in sweat.It can be difficult to formulate a ration to meet all of your horse’s mineral requirements. Supplementation in the form of commercial mineral mixes, is usually the most common and practical solution. I recommend a good, balanced mineral mix which is fed once a day with a small feed. Some people may choose to use blocks and licks. We don’t recommend these to our clients as you cannot be sure your horse receives their daily requirement. A lot of blocks also contain molasses to make them palatable and this should be avoided in horses and ponies prone to laminitis, those diagnosed with EMS or ones that are likely to gorge! (yes, my own clydesdale once ate a 10kg mineral block in one night!!)

8. Horses have a relatively small stomach compared to other species. They are not designed to consume large meals once or twice a day. Grazing allows horses to eat frequent small portions over the day. In humans, gastric acid secretion is stimulated by the presence of food (when we start eating a meal). However, in-between meals, there is very little acid secretion in humans. Horses, however, continually secrete gastric acid the entire day, even without the presence of food. Horses can produce up to 30-50L of acid per day which is neutralised when they are allowed to continuously graze. The problem arises when horses are not allowed to graze continuously. Acid is still being secreted, but without food to buffer the effects of acid, the stomach wall becomes eroded and gastric ulcers are formed. It is important that your horse has access to pasture or hay 24/7 to help prevent the development of equine gastric ulcers.

9. Knowing your horse’s body condition score (BCS) is essential when formulating your horse’s diet. BCS checks the amount of “covering” your horse has in certain anatomic areas such as withers, neck, loins etc. On average, you want to aim for a BCS of 4-6. This means that horses under 4 are considered underweight and those over 6 would be considered overweight. KER has an excellent chart on Body Condition Scoring.

10. Changes to your horse’s diet should be made gradually. This should ideally occur over the course of 14 days. Changes made any quicker than that will most likely cause digestive upsets such as colic. A gradual change allows the micro-organisms in your horse’s gut to adapt to the new feed.


 Changes to your horse’s diet should be made gradually.


11. Your horse is an individual and they should be fed that way. Even though all horses require the 6 classes of nutrients to survive, how much they require and in what proportion varies greatly from horse to horse. Important factors to consider when formulating your horse’s diet include their age, their activity level and their physiological state.

Use the information above as a starting point to understand your horse’s nutritional requirements. You should consult with a veterinarian who understands equine nutrition or a qualified nutritional advisor to help you formulate your horse’s diet.

If you have any questions or concerns, don’t hesitate to contact us on 0427 072 095.

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