The Hind Gut

Lately there has been talk about probios in a horses diet. To see why or if they need them we need to look at the horses anatomy. Once the digesta has moved through the small intestine most of the soluble products have been removed. What usually remains after the small intestine is fiber and ingestible portions.

So, after the small intestine the rest of the tract is called the hindgut. The cecum is the first of three large fermentation sacs and contains microbes. This is where bacterial degradation or fermentation begins and this fermentation produces volatile fatty acids. VFA’s are simple fats that enter the metabolism as a source of fat. 

Next is the colons. There are two colons: the dorsal and ventral colons. These are sacs that also continue the process of bacterial fermentation. The walls of the colons are also able to absorbed VFA’s and water soluble vitamins. The two large colons are joined by a small narrow transverse colon; this combination of large sacs joined by a small narrow pipe tends to cause blockages, also called impaction colic. The horse maintains an important population of beneficial bacteria in the hindgut. These bacteria break down the fibers. Because this hindgut is located after the small intestine in the GI tract, enzymes are no longer directly digesting the gut content, including bacteria. Therefore bacteria pass intact from the hindgut through feces— it’s the by-products of the bacterial digestion that the horse absorbs and uses. Anything that damages the bacteria will upset the vital balance. Drugs like dewormers, nonsteroidal anti-inflammatory drugs (NSAIDs) and oral antibiotics. Sudden food changes, dehydration, increased temperature, dehydration can overwhelm the good bacteria.

Probiotics supply beneficial bacteria in the form of dose of dried bacteria to the gut with the intention of resupplying good bugs. They are not needed to be fed every day; they are only necessary only from time to time, examples are following deworming, if drugs are being given orally, or if the horse overheats.  There are other products that “feed” the beneficial bugs and help them grow. One option is yeast. These can also be called prebiotics. Feeds that are high in soluble fiber help beneficial bacteria thrive. How ever if they grow too quickly then they can lead to over growth which is not a good thing. So like everything or the horse balance is key.