Jennifer Little BSc Hons MSc RNutr PgCert
Independent Equine Nutritionist


The phrase “creatures of habit” has frequently been applied to the horse, and where it comes to their digestive system this is certainly true. A horses digestive system can be split into two sections, the Foregut, where digestion is driven by chemical reactions. Then the Hindgut, where digestion is driven by microbes, including bacteria and protozoa. The numbers and balance of the different types of these microbes are collectively refereed to as the Hindgut Biome. The Hindgut Biome is primarily responsible for converting fibre from the diet into energy for the horse. But, it also influences the functioning of the immune system, inflammatory status, healing rates, production of certain vitamins and even a horses fight flight response. For all the things the Hindgut Biome can do, one thing that it struggles to do, is adapt quickly to changes.

If changes to the diet or management occur faster than the hindgut biome can adapt, it can result in a cascade of affects. Firstly, the increase in a group of bacteria with the Hindgut Biome, know as Amylolytic bacteria. This group of bacteria produce Lactic acid, causing the hindgut to change to a acidic environment, a condition know as hindgut-acidosis. This change damages and even kills off the good bacteria, which in turn releases toxins as they breakdown. The combination of the lactic acid and these toxins are associated with irritation and inflammation of the gut wall, reducing its protective barrier capabilities. This is in tern linked with increased colic risk, infection rates, and elevated fight flight responses. It is also associated with decreased body condition, apatite, poor healing rates and reduced performance.

A common change that can threaten the health and balance of the hindgut biome is a quick change to a horses diet. All changes should occur over a transition phase, where the current diet is weaned out in stages, while the new diet is introduced, till a full switch over has occurred. In relation to most bucket feeds this process should occur over at least 1 week, but in relation to forage sources changes should take at least 2 weeks. It is easy to comprehend how a change to a bucket feed can be easily controlled, but there are several factors that mean achieving the same control with regard to forage sources can be far more challenging. In relation to preserved forages such as Hay or Haylage, observing a transition period when introducing it into the ration, changing batches, or even when moving from one bale to the next can all support retaining gut health.

A major conflicting factor for controlling changes to a horses diet, especially their forage source, is undoubtedly the weather. Recent years have seen climate records frequently broken, with hottest years, driest summers, wettest winters and greatest temperature differences within 24 hours. All of which can impact grass growth, richness, and even the nutritional variability in the hay/haylage produced. Sudden changes in the weather can result in horses management needing to be changed faster than ideal. Requiring grass to be switched for hay/haylage, turnout time needing to be changed for stabled time, and even needing to switch horses from one field to another quickly. Increasing the risk of hindgut- acidosis developing.

Observing a transition period and ensuring a balanced diet is considered gold standard for supporting gut health. Although it can be advisable to provide additional support for the hindgut Biome, especially during periods of change. One well researched and documented way of providing this additional support is the the supplementation of the Pro-biotic, Saccharomyces cerevisia. This probiotic is a specific yeast that creates an environment within the horses hindgut that is more suitable for the beneficial bacteria, restoring the balance of the hindgut Biome, and even increase a horses ability to manage change [1;2;3;4].


[1] Chaucheyras-Durand, F., Sacy, A., Karges, K., Apper, E. 2022 Gastro-Intestinal Microbiota in Equines and its role in health and disease: the black box opens. Microorganisms (10) 2517
[2] Coverdale, J.A., 2016. Horse species sympposium: can the microbiome of the horse be altered to improve digestion? J. Anim. Sci. (94) 2275-2281
[3] Geor, R.J., Harris, P.A., & Coenen, M., 2013 Equine Applied and clinical nutrition. Health welfare and performance. Saunders Elsevier, 575-576
[4] Newbold, C.J., Wallace, R.J., McIntosh, F.M., 1996 Mode of action of the yeast Saccaromyces cerevisiae as a feed additive for ruminants Br. J. Nutr. 76, 249-261

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