The cornerstone of good nutrition is a balanced diet. Clare MacLeod MSc RNutr, independent equine nutritionist, explains why vitamins and minerals are essential

The cornerstone of good nutrition is a balanced diet. A balanced diet is one that supplies all the essential nutrients that a horse needs every day, without net gain or loss. Ensuring an adequate supply of energy, protein, carbohydrates (including fibre) and lipids (oils and fats) is easier in horse diets than ensuring enough vitamins and minerals. Grass and preserved forages such as hay are always short of some essential minerals and – in the case of preserved forages – vitamins, no matter how well the forage is cultivated or processed.

What are vitamins and minerals?

Vitamins and minerals are classed as essential micronutrients, since they are required in smaller amounts than carbohydrates or protein (the macronutrients). They are essential because deficiencies cause disturbed body function and eventually disease.

Vitamins have a variety of functions in the body and vitamin activity can be found in a variety of related substances. Fat soluble vitamins include vitamins A, D, E and K. Water soluble vitamins include vitamins C and B-complex. Vitamins are not a health boost, tonic, or detox; they are essential for basic good health.

Minerals are inorganic elements that have a wide range of functions in the body, from giving hardness to bones and teeth, balancing body fluid, components of enzymes and basic cellular activity. Essential minerals make up about 4% of the horse’s bodyweight. Due to the way they are absorbed, they interact in complex ways and their ratios in the diet are as important as the actual intake. Some minerals are toxic in excess, and supplementation – especially of single minerals – should always be done with care. Essential macrominerals (required in grams daily) include calcium, phosphorus, magnesium, sulphur, and the electrolytes potassium, sodium and chlorine. Essential microminerals (required in milligrams daily) include zinc, copper, iron, selenium, iodine, manganese, and cobalt.

How to feed correct levels of vitamins and minerals

Horses and ponies are healthiest on a forage-based diet, and they are generally fed vitamin and mineral-fortified concentrate feed or a balanced vitamin and mineral supplement to make up for what cannot be supplied by the forage. What goes into the feed bucket should simply balance the shortages in forage.

Horses and ponies who do not require the full recommended amount of fortified concentrate feed i.e. who get almost enough energy and protein from forage, must be fed a source of vitamins and minerals in order to receive a balanced diet. The safest and most useful way to supplement essential micronutrients is with a well-formulated multi-vitamin and mineral supplement. These can be fed mixed with a little chaff or feed to horses who obtain enough energy and protein from forage alone, or added on top of compound feed for those who require less than the full recommended amount.

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Balance the diet first

Vitamin and mineral supplements are the most underused and most misunderstood supplement. They should be on the shelf of every tack and feed store! You can’t always see the different straight away, but the horse’s body will feel the difference and long term health will suffer without enough. Before feeding a boost like extra iron (which can actually be harmful), a hoof supplement or any other therapeutic addition, firstly make sure the basic diet is balanced, since the body cannot function correctly without adequate essential vitamins and minerals.

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Selenium is an essential trace element but, unlike most nutrients, it has a low-toxicity threshold. Care is required to achieve the right balance between the correct amount and over-supplementation. The authorities also take a prudent view and list only certain forms of selenium for use in feeds and supplements.

Selenium is best known as an antioxidant, but it has other roles including iodine metabolism, repair of DNA and in the immune system (although this may be linked to its antioxidant properties).

As an integral part of the enzyme glutathione peroxidase, selenium’s antioxidant role is within the cells of the body to prevent the formation of free radicals. It is often mentioned with vitamin E because both nutrients work within the cells to prevent free radical damage. A deficiency of one increases the requirement for the other, and vice versa.

Horses typically require 0.1mg/kg selenium in the total diet when inactive, increasing to 0.3mg/kg in exercising horses and broodmares.

UK soils, and the plants that grow in them, are generally low in selenium, so forages and cereals typically have low selenium contents (0.1 mg/kg). As a result it is often necessary to add selenium to the diet via hard feed or supplements.

A classic sign of selenium deficiency is white muscle disease in foals and young stock. The mare transfers selenium to the foetus during pregnancy and passes more to the foal through her milk. She must receive plenty of selenium (via a dietary supply above 0.05 mg/kg) throughout her gestation to set the foal up for early life.

At the other end of the spectrum, the first signs of toxicity are poor hoof quality and pain around the coronet band, although the classic signs are the sloughing off of hooves and loss of mane and tail hair.

Selenium specifics

• Compound feeds are generally supplemented with selenium at levels of 0.2-0.3mg/kg feed. The selenium source is sodium selenite. The EU has recently banned selenium yeast
• Supplements, particularly those supplying antioxidant or immune system support, can typically supply 1mg selenium per dose
• A healthy adult horse eating 10-12kg of compound feed and forage per day will consume about 2mg of selenium per day, before supplement addition
• The toxic threshold for selenium is as low as five times the requirement. Double-dosing — giving supplements and feed that both contain selenium — may approach toxic levels

Horses that receive plenty of fibre in their diet create their own supply of B-vitamins, which are synthesised by the micro-organisms present in the hindgut. As long as there is plenty of fermentation of fibre in the intestinal tract, the supply of B-vitamins will be plentiful.

However, if this internal manufacture (and absorption) is disrupted in any way, then a deficiency in several of the many B-vitamins that exist can occur and supplementation may be beneficial.

Disruption to the fermentation of fibre in the hindgut can take place for a number of reasons: a low-fibre diet being a prime example. Other instances include any undue stress, such as when horses don’t travel well, or through illness, rapid growth or following surgery or heavy antibiotic use. Antibiotics can do a good job of wiping out some of the microbial population in the hindgut.

Competition horses and racehorses are examples of horses that may well be deficient in B-vitamin production: a compromised gut micro flora due to a low-fibre, high-starch diet on top of the stresses of training and the excitement of competition or race day. Indeed, some scientific studies have proven this to be true.

Other candidates for B-vitamin supplementation are older horses with poor teeth that cannot chew their fibre well, or horses recovering from illness or surgery that have had a hindgut disturbance.

Breakdown of B-vitamins

• Vitamin B12: vital for enzyme function and for fat, protein and carbohydrate metabolism. Also required for the formation of blood cells and amino acids
• Folic acid: works closely with vitamin B12 to produce red blood cells and haemoglobin
• Vitamin B6: (pyridoxine) is essential for energy production, nervous system activity and for blood production
• Vitamin B1: (thiamin) is also required for fat and carbohydrate metabolism
• Vitamin B2: (riboflavin) again vital for protein and carbohydrate metabolism
• Niacin: supports healthy skin and digestion, and again important in energy transfer. Signs of deficiency include a loss of appetite and diarrhoea
• Pantothenic acid: used in the production of antibodies and energy metabolism
• Biotin: again necessary for energy and protein metabolism and shown also to have a positive effect on hoof condition at high levels (15mg per day for at least nine months)

This feed forum feature was first published in Horse & Hound (28 October, 04)

Although your horse may be looking and feeling great on a diet of grass alone, he is almost certainly not receiving all the vital nutrients he requires. Spring and summer grass can provide sufficient energy and protein for horses in light to medium work but in many cases key minerals such as copper, manganese and zinc will be lacking.

These essential minerals are required for bone function, haemoglobin and enzyme formation and energy metabolism – to list but a few – and will need to be supplemented, even in spring and summer.

Terms such as bioplex, proteinated or chelated minerals are fashionable at the moment, but what exactly do these terms mean and more importantly, how will feeding them benefit your horse?

A “bioplex mineral” is an individual mineral molecule, such as zinc, copper or manganese, which has been chemically combined with an organic compound, typically an amino acid.

Research has shown that this process renders the minerals more biologically active than standard inorganic minerals. In addition, these organic molecules are between 20-75% more available to the horse. This is because horses digest and absorb the majority of amino acids and simple sugars from their small intestines. As amino acids are absorbed very well, the attached mineral can be easily and efficiently transported across the gut lining.

Secondly, the horse naturally bonds the majority of minerals in its diet to proteins prior to and during digestion. By providing the minerals already bound to a specifically selected protein the efficiency of the absorption process will be increased.

Furthermore, research has demonstrated that when bioplex minerals are fed in conjunction with the inorganic form of the mineral (as a certain percentage of the total diet) the utilisation and efficacy of the bioplex mineral is maximised.

Benefits of including bioplex minerals in the diet of your horse include:

• Increased resistance to stress and disease
• Improved soundness
• Improved coat and hair condition

Ever had a horse go off its feed or lose its enthusiasm for work? Or maybe you have a competition horse that receives plenty of food, but still has poor feet.

These problems could be related to B-vitamins — essential nutrients required in minute amounts to regulate a large proportion of the body’s metabolism. You may think that if they are only required in tiny amounts then they’ll always be present whatever is fed, but this is not always the case.

The horse has its own internal B-vitamin generators in the form of the micro-organisms that populate its large intestine. In healthy diets, these are well capable of supplying all a horse needs. However, when demand outstrips supply, or when the hindgut isn’t functioning effectively, supplies can be marginal at best.

Research has revealed clinical deficiency of vitamin B1 in sheep when high-starch diets affect microbial fermentations. The same effect is guaranteed in the horse, as the principles are the same.

Appetite and movement are affected because B-vitamins are involved in the metabolism of energy, and if insufficient are supplied the horse can become fatigued easily.

Hoof quality can also be affected as biotin, which is well known for its beneficial effects on hoof quality, is also a B-vitamin.

B-vitamin facts

Situations where B-vitamin production can be impaired:

• Diets where low levels of forage and/or high amounts of cereals are fed
• Horses in hard work
• Hay or haylage that isn’t palatable leads to poor forage intakes
• Unsupplemented oats diets
• After eating bracken (which contains an enzyme that destroys vitamin B1)
• After having antibiotic therapy
• Poorly stored (ie exposed to heat and light) feeds

Where to find B-vitamins:

• commercially prepared feeds and supplements
• Naturally produced by the digestion of adequate amounts of fibre (more
  than 1% of bodyweight per day) in the hindgut
• It is difficult to provide too many B-vitamins, as they are water soluble, and any excess is excreted in the urine.

This article was originally published in Horse & Hound (22 January).

Vitamins are organic compounds required by horses in tiny quantities to maintain good health. They can be divided into two types:

• Fat soluble — vitamins A, D, E and K, which can be stored in the body
• Water soluble — B vitamins, biotin, choline, inositol and vitamin C

B vitamins are synthesised by micro-organisms in the hind gut and cannot be stored by the horse. Despite this B vitamin deficiencies are rare in healthy horses kept on a well-balanced, high-fibre diet, although horses in intensive training, such as eventers and racehorses, may benefit from supplementation

Vitamin B12 (cobalamin)

Use: Vitamin B12 is a complex vitamin vital for enzyme function and metabolism of fat, protein and carbohydrate. It is synthesised by micro-organisms in the horse’s gut and is also required for blood cell formation and the production of amino acids.

Signs of deficiency: Loss of appetite and faulty metabolism.

Folic acid (folate)

Use: This was formerly known as vitamin Bc and works closely with vitamin B12 to produce red blood cells and haemoglobin.

Signs of deficiency: Poor growth and anaemia, although deficiency is rare in horses.

Vitamin B6 (pyridoxine)

Use: This vitamin affects the nervous systemand is essential for energy production, the metabolism of protein and carbohydrates, nervous system activity, production of blood, plus protein breakdown and build up.

Signs of deficiency: Faulty metabolism within the gastro-intestinal system, loss of muscular tone and nerve coordination, roughened coat.

Vitamin B1 (thiamin)

Use: This vitamin is required for fat and carbohydrate metabolism and deficiencies can result in anxiety, stress and lack of energy. It is often incorporated into supplements as a calmer.

Signs of deficiency: Anaemia, bladder incontinence due to nervous irritability, capillary weakness in the blood vessels, nervousness and irritability, dry skin and staring coat. Also gastric disturbances,skipped heartbeats or abnormal slowing of the heart rate (bradycardia), loss of appetite and weight, ovulation problems in mares.

Vitamin B2 (riboflavin)

Use: Vitamin B2 is vital for the metabolism of proteins and carbohydrates and nervous system function, and is found naturally in leafy, green hay.

Signs of deficiency: Tongue ulcerations, degenerative changes within the colon, eye problems such as cataracts, faulty carbohydrate metabolism, inflammation of gums, secondary anaemia within the blood vessels.

Vitamin B3 (niacin: nicotinic acid and nicotinamide)

Use: Niacin promotes healthy skin and digestion, and is important for the metabolism of carbohydrates, fats and proteins.

Signs of deficiency: Anaemia within the blood vessels, digestive disturbances, loss of appetite.

Vitamin B5 (pantothenic acid/pantothenate)

Use: This is required for the production of antibodies for immunity, and also the metabolism of carbohydrates, fats and proteins.

Signs of deficiency: Can result in skin disorders and weight loss.

Sorbitol

Use: Sorbitol is a carrier, specifically for vitamin B12, and enhances vitamin absorption.

Signs of deficiency: Deficiency in horses is rare.

Choline and inositol

Use: Choline and inositol are vital for a healthy liver and help the breakdown of fat, resulting in healthy hooves and coat and the elimination of toxins.

Signs of deficiency: Deficiency in horses is rare.

BiotinUse: Part of the B vitamin group, biotin is necessary for the metabolism of protein, fat and carbohydrate and increases production of keratin in the hoof by breaking down protein.

Signs of deficiency: Poor hoof growth, heel cracks, fissures and ridging of the hoof wall.

Q: My farrier has advised I feed a biotin supplement. Could you tell me a bit more about biotin and how it helps the horse?

Nutritionist Christine Smy replies: Biotin is a sulphur containing B vitamins, which is particularly useful in maintaining good horn growth.

Horses manufacture B vitamins in the large intestine during the breakdown of fibre, and the absorption of these vitamins, added to those obtained from a well-balanced diet, usually provides adequate levels for the horse.

Biotin is a water-soluble vitamin and is not stored in the body for any period of time. It is either used by the body cells or excreted in the urine. Therefore, if your horse has poor feet, biotin should be added daily to the diet, preferably at 15mg per daily dose as this is the level needed to produce quality horn.

When choosing a hoof supplement, avoid those which contain just biotin as there are other elements which should be added as a complement. These include zinc, calcium and methionine.

Only two per cent of horses with hoof problems have a biotin deficiency and, by adding biotin alone, the hoof takes longer to repair than with all four elements.

Finally, a hoof will take between nine to 12 months to re-grow, so don’t expect to see results immediately.

Q: I own a five-year-old 15.2hh cob mare who is currently in light work and competes occasionally at the weekends. She is kept at grass and is fed 1⁄2lb of pasture mix and has access to a salt lick. She has recently begun chewing the bark of a sycamore tree in her field. Although I have tried covering the base (the part she’s chewing) with mustard, waste oil and hoof oil, she still insists. I have never encountered this problem before and need some advice.

Nutritionist Kate Jones replies: Chewing trees and licking soil is a common problem in horses at grass and it usually relates to a diet deficiency. Modern pasture is limited as it normally only contains one or two species of grass and perhaps a legume, such as clover. Compare this with the hundreds of species of grasses, legumes, herbs, shrubs and trees in the wild and you see how deficiencies can come about.

Additionally, in certain areas of the country, a nutrient deficiency occurs in the soil, which is in turn passed to the grazing and local hay. Your horse’s problem will be compounded by low levels of hard feed, which provide important vitamins and minerals for those on a high-concentrate diet.

To combat these contributing factors, I recommend you introduce a general-purpose supplement to the feed daily, to supply whatever missing goodness your mare is seeking from the tree bark.

Unfortunately, once habits like these are in place, they are often hard to break. You may find it necessary to fence off that particular tree until she has learned that she is getting all she needs in her bucket.

Q. I keep my horses on the Welsh borders. We’re always being told this area is deficient in selenium and many horseowners are feeding a selenium supplement. Why is selenium so important for horses when it’s needed in such small amounts?

Christine Smy replies: Selenium is a trace element and horses only require milligrams in their diet. It is essential in animal and plant metabolism but there are selenium deficient areas in the UK.

Selenium is present in all grains and hays but the levels depend on the amount of selenium in the soil on which they were grown.

It is essential for:

• Immunity
• Growth of youngstock
• Reproduction
• Producing antioxidants which, when working in conjunction with vitamin E, protect the body from damage.

If your horse isn’t getting enough selenium, he may suffer with problems such as tying up. Infections and wounds may take longer to heal and muscular cramping and muscle degeneration may also be apparent.

Many vets recommend selenium and vitamin E is fed to a horse proneto tying up. This can help but tying up has many causes and these should also be addressed.

Take care if feeding a selenium supplement. Selenium is toxic in high levels causing apparent blindness, staggering, colic or even death. If high levels are fed over a long period of time, chronic poisoning may be apparent in loss of mane and tail hair and separation of the hoof wall from the foot at the coronary band.

If you’re feeding 3-4kg (7-9lb) a day of good quality concentrate, you should be providing your horse with adequate selenium levels.

Many people feed a selenium and vitamin E supplement plus a broad spectrum supplement which also contains selenium. If this is the case, speak to a nutritionist to see if you are exceeding recommended levels of selenium in the diet.

Read more equine supplement advice:

• Feeding copper supplements
• Q&A: Why feed garlic?
• Feeding linseed