Updated: Jun 14, 2019
Feed To Maintain Diversity.
Your horse's hind gut is home to trillions of bacteria, archaea, viruses, yeast, mold, fungi and bacteriophages. They have many different jobs to do, one of the most important ones is to interact with the immune system, around 80% of the entire immune system lives in the lining of the gut, the biome communicates with it constantly. The strength of the immune system relies on having a biome that is rich in different species, this is called richness, at the same time the different species should have a sufficient number of each, this is called diversity.
To maintain or increase richness and diversity the horse needs to eat a complex diet, full of different plants, herbs and hedgerow plants.
Tip: Feed hay and pasture containing a wide variety of different plant species, if this type of hay or pasture is difficult to find, take the horse grazing in hand on a wide verge or in the hedgerow
Feed plenty of plant polyphenols.
Polyphenols are found in most plant material, though some are higher than others, plants with a medicinal value such as oregano, thyme and rosemary are especially high. Once eaten the horse's body recognises them as being indigestible or 'xenobiotic' this means the polyphenols from these plants have low 'bioavailability' compared to other nutrients such as carbohydrates, proteins and glucose. Though a very small proportion of polyphenols 5% can be broken down and absorbed in the small intestine, 95% reaches the large intestine and the caecum in tact. Once in the caecum the gut bacteria produce enzymes to help digest them.
Polyphenols that are antimicrobials are selected by the bacteria specifically to help reduce pathogenic bacteria.
Tip: Don't micromanage the diet rather, provide diversity, lots of different herbs and other plants with medicinal properties will provide the variety needed by the gut bacteria. The gut bacteria will self select what they need to control the pathogens.
Feed the gut bacteria that help maintain the gut wall.
Adding a variety of plant polyphenols to the diet, described above, will help to restore and maintain the bacteria that maintain the gut wall. The gut wall bacteria also like a supply of inulin, found in sugar beet and other root vegetables such as carrots, inulin can be added to the diet at a dose of 21g x 3 daily. The best wild plant source of inulin can be found in wild chicory, especially high in inulin after flowering, why not plant a meadow mat containing chicory? https://www.meadowmat.com/
Feed to help improve the metabolism
The majority of horses not involved in fitness work or competition have low levels of the bacteria that are linked to metabolism, increasing the exercise does increase the levels of these bacteria. There are plants that help to increase the metabolic bacteria, these are found in the bitter plants, such as bracken, ivy and ferns, as only small amounts are needed it is possible that allowing the horse to snatch what he needs whilst out on a hack will provide enough for his needs. The compound linked to an increase in metabolism is a plant steroid called ecdysterone, it has anabolic activity (increases metabolism and muscle mass) but isn't androgenic (doesn't impact the sex hormones so no unpleasant side effects). This compound can be found in wild and cultivated spinach, the roots and seeds contain the highest amounts.
Tip: Only 200 mg per day are needed to make the difference to the levels of verrucomicrobia bacteria in the gut, though this amount is small it does equate to rather a lot of seeds and roots and may be better introduced by feeding it as a supplement to start with.