The Green Horseman

• Unlike humans horses are hindgut fermenters which means their food is primarily digested through fermentation in the cecum. Humans have little ability to digest fiber.
• Horses need to eat between 1.5-3% (1% at the absolute minimum) of their bodyweight daily. For the average horse that’s about 15-30 pounds.
• Daily diets that consist 30% or more of cereals (oats, barley, corn, concentrates, etc) can have a negative impact on the horse’s ability to digest fiber

• Feeding MORE than 200g starch/100kg BW/meal can result in 70-150g/100gBW/meal of undigested starch reaching the hindgut
• When starch is fermented it creates volatile fatty acids (VFAs) which have pH of about 4.8 (acidic). These VFAs can damage the lining of the GI tract.

• 80% of ulcers occur in the upper half of the stomach that is not protected
• The horse can make 1.5liters of stomach acid EVERY HOUR

• Equine saliva contains CaCl which helps buffer stomach acid
• With the right conditions horses can produce 9-11 gallons of saliva every day. This is one major reason why grazing is so important to the horse. Grazing and nibbling creates more saliva.

• The horse’s stomach is only 8-15 liters (2-4 gallons) in size
• When fed intermittently the horse’s stomach pH drops in about 5-6 hours. The acidic environment puts the horse at risk for ulcers
• Studies have shown that when the colonic pH drops (more acidic) horses display more anxiety-like behaviors
• The horse’s digestive system is the host of a quadrillion microorganisms that aid in the breakdown of food

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REFERENCES AND FURTHER READING

• Andrews, F., Buchanan, B., Elliot, S., Clariday, N.A., & Edwards, L. (2005). Gastric ulcers in horses. Journal of Animal Science, 83.
• Julliand, V., Fombelle, A. de, & Varloud, M. (2006). Starch digestion in horses: The impact of feed processing. Livestock science, 100, 44-52. doi: 10.1016/j.livprodsci.2005.11.001
• Santos, A. S., Rodrigues, M. A., Bessa, R. J., Ferreira, L. M., & Martin-Rosset, W. (2011). Understanding the equine cecum-colon ecosystem: current knowledge and future perspectives. Animal : an international journal of animal bioscience, 5(1), 48–56. https://doi.org/10.1017/S1751731110001588
• Ericsson, A., Johnson, P., Lopes, M.A., Perry, S.C., & Lanter, H.R. (2016). A Microbiological Map of the Healthy Equine Gastrointestinal Tract. PLoS ONE, 11.
• http://www.omafra.gov.on.ca/english/livestock/horses/facts/info_digest.htm
• https://hygain.com.au/blogs/library/horses-digestive-system
• https://ker.com/equinews/nothing-spit-saliva-most-natural-stomach-buffers-horses/