Nutrition: protein in Horses (Equis) | Vetlexicon
equis - Articles

Nutrition: protein

ISSN 2398-2977

Podcast: Nutrition: protein


  • Protein is essential for maintenance, tissue growth and milk production.
  • Both quantity and quality of protein are important - quality refers to the levels of essential amino acids a feedstuff provides, and their availability to digestive enzymes.
  • Essential amino acids are those that the horse cannot manufacture in sufficient quantities to meet requirements and so they have to be supplied in the diet.
  • Lysine is the essential amino acid most likely to be deficient in horse diets and threonine is the next most likely.
  • Cereals are typically low in essential amino acids and so good quality protein sources should be added to straight cereal rations.
  • Soya, alfalfa and synthetic lysine are typically added to compound feeds to provide quality protein.

Growth and maintenance

  • Requirement greatest, relative to energy requirements, at the period of maximum growth rate - between 3 and 6 months of age   Nutrition: growth  .
  • If mature weight is 450 kg, 100 kg is gained at 3-6 months.
  • Growth rate decreases as age increases - gain of 100 kg from 6-12 months; then 75 kg from 12-18 months.
  • A maximum weight gain has been achieved with colts aged 3 months with a diet containing 140-150 g protein/kg, 7.5 g lysine/kg and 5 g threonine/kg.
  • Thoroughbred   Thoroughbred  and Quarterhorse   Quarterhorse  yearlings require 0.45 g lysine/MJ of digestible energy (DE).
  • Dietary concentration of 20% protein (NRC recommends 14%) has not been shown to be harmful, but dietary protein of 9%   →   depressed growth, bone turnover, feed intake and feed utilization.
  • No relationship has been found between the amount of protein in the diet and laminitis   Foot: laminitis  .
  • In a mature horse, the protein required for maintenance = no net gains or losses of body nitrogen.
  • A horse weighing 400 kg thus requires 10 g crude protein/MJ DE/day at maintenance.
  • See also nutrition for:

Dietary protein concentrations

  • Crude protein as g/kg 90% dry matter diet.
  • Mature horse - 72 g.
  • Mare first 3 months gestation - 72 g (non-lactating).
  • Mare last 90 days gestation - 95 g.
  • Mare last month gestation - 100 g.
  • Mare lactating, foaling to 3 months - 125 g.
  • Mare lactating, 3 months to weaning - 100 g.
  • Foal at 3 months - 131 g.
  • Yearling at 12 months - 113 g.
  • Long yearling at 18 months - 101 g.
  • Two year old in light training - 101 g.
  • Levels in pasture, hay or concentrate can be calculated from tables of chemical compositions of feedstuffs or can be sent for nutritional analysis.

Sources of protein

  • Protein concentrates from various plant sources:
    • Peas.
    • Beans.
    • Soyabean.
    • Cottonseed.
    • Linseed.
    • Sunflower seed.
    • Rapeseed.
    • Dried forages, eg alfalfa.
  • Milk protein products are used in foal feeds.
  • Fishmeal is now rarely used in horse feeds.
  • Proteins from micro-organisms may be available in the future. Several species of bacteria and yeasts have been cultured for this purpose and the protein is of high quality. However, bacterial protein is high in purines and pyrimidines, precursors of uric acid.

Print-off the Owner Factsheet onNutrition - keeping your horse on top form  Nutrition - keeping your horse on top form  to give to your client.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hintz H F (1992) Ed. Clinical nutrition. Vet Clin North Am 6, (2).
  • Schryver H F et al (1987) Growth and calcium metabolism in horses fed varying levels of proteinEquine Vet J 19 (4), 280-287 PubMed.
  • Orton R K, Hume I D & Leng R A (1985) Effects of level of dietary protein and exercise on growth rates of horses. Equine Vet J 17 (5), 381-385 PubMed.

Other sources of information

  • Frape D (2004) Equine Nutrition and Feeding. 3rd edn. Blackwell Publishing Ltd, UK. ISBN: 1405105984.