Nutrients

Horse feeds are made up from a number of different constituents from which energy and other nutrients can be derived.

These ‘nutrients’ are divided into two main groups;

– Macro-nutrients – Carbohydrates, Lipids (fats and oils), Proteins and Water,

– Micro-nutrients – Vitamins and minerals.

The Macro-nutrients

1. Carbohydrates 

Carbohydrates can be defined as neutral chemical compounds containing the elements carbon, hydrogen and oxygen. (McDonald, et al., 2002)

All carbohydrates are formed from saccharide units, and named accordingly.  See table below.

SUGARS Monosaccarides Trioses Glucose
Tetroses Fructose
Hexoses Mannose
Galactose
SUGARS Oligosaccharides Disaccharides Sucrose
Lactose
Maltose
Trisaccharides Raffinose
Kestose
NON-SUGARS Polysaccharides Homoglycans Fructans
Galactans
Starch
Glycogen
Cellulose
Heteroglycans HemicellulosePectic substances
NON-SUGARS Complex Carbohydrates Glycolipids
Glycoproteins

Table 1 – Classification of Carbohydrates. (Adapted from McDonald, et al., 2002)

a. Hydrolysable Carbohydrates / Non-Structural Carbohydrates (NSC) 

These carbohydrates can be digested in the horse’s small intestine and include, hexoses, disaccharides, some of the oligosaccharides group, as well as non-resistant starches (starches that can be broken down by enzymes in the stomach).

b. Fermentable Carbohydrates / Structural Carbohydrates 

Fermentable carbohydrates are referred to as those carbohydrates that confer ‘structure’ to plants.  (Bishop, 2005) They are also termed ‘fibre carbohydrates’ or just ‘fibre’.

These carbohydrates are digested in the equine hindgut by microbial activity.

2. Lipids (fats / oils)

In equine nutrition, fats or oils are referred to as lipids.   They are made up from carbon, hydrogen and oxygen, like carbohydrates.

Horses can digest lipids very well.  Various studies have shown that horses can tolerate up to 20 per cent lipid in the overall diet.

They are an excellent ‘safe’ energy source, providing approximately two and a half times more energy in comparison to carbohydrates.

In addition, lipids as a fuel source allow precious muscle and liver glycogen stores to be spared.

3. Protein

Proteins are described as complex, organic compounds. (Cuddeford, 2003)

When hydrolysed in the equine body, proteins are broken down in to ‘amino acids’ .

The horse requires approximately twenty-two different amino acids, some of which they can produce themselves (called ‘non-essential’) and others which must be provided through their diet (termed ‘essential’) as they cannot be synthesised within the equine body.

Quality protein has a high level of essential amino acids.  They perform a variety of roles in the body – necessary for structure, storage, defence and other key bodily functions.

4. Water

Although, obvious, water, is a key nutrient in your horse’s diet and surprisingly often gets overlooked. The amount of water to provide will depend upon what the horse is being fed and how it is kept.  For example, a horse grazing lush spring grass might not need additional water to be supplied in its diet as it can obtain all its requirements from the grass.  Whereas a stabled horse on a forage only diet, will most certainly require additional water.

It is worth remembering that without an adequate supply of water, no matter how hungry, a horse will not eat.

The Micro-nutrients

1. Vitamins

Vitamins are usually defined as ‘organic, compounds that are required in small amounts for normal growth and maintenance of animal life.’ (McDonald, et al., 2002)

They are divided in to two groups:– Fat-Soluble and Water-Soluble – relating to how the equine body absorbs the particular vitamin.  Water-soluble vitamins, for example, are absorbed in to the bloodstream, whilst fat-soluble vitamins are absorbed in association with fat.

a. Fat-Soluble Vitamins

Vitamin / Chemical Name:-

Vitamin A – Retinol

Vitamin D2 – Ergocalciferol

Vitamin D3 – Cholecalciferol

Vitamin E – Tocopherol*

Vitamin K – Phylloquinone**

b. Water-Soluble Vitamins

Vitamin B Complex – Thiamin

Vitamin B1 – Riboflavin

Vitamin B2 – Nicotinamide / Pyridoxine

Vitamin B6 – Pantothenic acid / Biotin / Folic acid / Choline

Vitamin B12 – Cyanocobalamin

Vitamin C – Ascorbic acid

Note:-

* A number of tocopherols have vitamin E activity.

** Several naphthoquinone derivatives possessing vitamin K activity are known.

(Adapted from McDonald et al., 2002)

2. Minerals

Minerals can be divided in to two sub-groups:-

a. Macro Minerals 

Macro minerals are expressed as a percentage  (%) (or sometimes parts per hundred) and are necessary for body structure, maintaining fluid balance, nerve conduction and muscle expansion/contraction.

They are required in the diet in larger amounts than micro (trace) minerals.

b. Micro (trace) Minerals

Micro minerals are expressed as mg/kg (or sometimes parts per million) and  are necessary as components of “metalloenzymes”, which are involved in controlling a large number of biological recations.

They are required in the diet in smaller amounts than macro minerals, but are no less important.

 

References:-

Bishop, R., (2005) The Horse Nutrition Bible, Cincinnati, David & Charles, subsidiary of F+W (UK) Ltd.

Cuddeford, D., (2003) Equine Nutrition, Marlborough, The Crowood Press Ltd.

McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., Morgan, C.A., (2002) Animal Nutrition, 6th Edition, Harlow, Pearson Education Limited.