Know your horse's feed! - Macro-nutrients and their sources

06.10.20

Know your horse's feed! - Macro-nutrients and their sources

Horses just like humans require the intake of food to provide adequate amounts of nutrients for growth, maintenance and to sustain performance. As a matter of fact there are 40 different nutrients the horse requires to be healthy; these nutrients are grouped in six major categories: carbohydrates (incl. fibre), fats, proteins, vitamins, minerals and water. Some of these nutrients are required in much larger amounts such as fibre, carbohydrates, fat and protein and are therefore called macro-nutrients. The table below highlights key aspects of each nutrient and gives examples of dietary sources. It should be noted, however, that each of these ingredients/sources also contain other macro-nutrients to varying degrees (e.g. hay is primarily a source of fibre yet it contains some starch, sugar, protein and fat).

Type of energy	Products of Digestion	Main functions	Risk of excess	Dietary source
Fibre Fermented in large intestine	Volatile Fatty Acids (VFA)	· Major source of energy · Contribute to stored energy · Support the fat reservoir	*	· Hay · Pasture · Chaff · Beet pulp · Soybean hulls
Carbohydrates (sugar + starch) Enzyme digestion in small intestine	Glucose		· Increased hindgut acidity · Ulcers · Laminitis · Colic	· Cereal grain (oats, barley, maize) · Molasses · Pollard/bran · Mill run · Honey
Fat Enzyme digestion in small intestine	Fatty acids	· Stored as an energy reserve · Carrier for fat-soluble vitamins	Obesity	· Rice bran · Vegetable oil
Protein Enzyme digestion in small intestine	Amino acids	· Tissue building and replacement · Protein is not an effective energy source	Build-up of ammonia which can cause respiratory disorders (in stables with poor ventilation)	· Lucerne · Soybean meal · Lupins/beans · Cottonseed meal · Canola meal

* Whilst there are no risks associated to excess of fibre, there are risks of excessive consumption of fibrous feeds such as pasture and conserved forages that may be high in starches and sugars for instance As presented in the table, the various feeds a horse consumes serve multiple purposes including the supply of energy, building and maintaining body tissue and regulating body processes. Whether you are after a feed rich in fibre for optimal gut health, in protein for muscle development or in fat for maximal energy efficiency, looking at the composition of various ingredients can be of crucial help. The graph below shows the macro-nutrient composition of various cereal grains and legume seeds typically used in commercial horse feeds. Most nutritionists suggest you should feed a bare minimum of 1.5% of your horse’s body weight per day in roughage, which refers to feeds with a fibre content of over 20% fibre. This means for the average 500kg horse you would feed at least 7.5kg of roughages such as hay, chaff and pasture, per day. If the horse is spelling or in light work most of its diet should come from roughages with some small supplementation to maintain vitamin and mineral balances. When a horse is in medium to intensive work you may need to add energy dense feeds such as fats and extruded or micronized grains. Remember to base your horse’s diet first on at least 1.5% of its body weight in roughage and only then add a more energy dense feed to meet your horse’s body condition and exercise regime.