We often have enquiries from anxious owners asking why their horse has suddenly been seen eating horse droppings. Their immediate reaction is to question if something is lacking in their horse’s diet. Well it possibly could be, but it’s probably not what you think it is!The first question most owners ask is if their horse is lacking in certain vitamins or minerals, and is it ‘seeking’ these missing elements by eating other horse’s manure. Horse manure is not exceptionally rich in vitamins and minerals, so it’s most unlikely to be the reason. So why are they eating the manure then?We may need to look at human research and human poo to find the answer! If we consider the latest human research, we now know that an adult consists of approximately 10 trillion human cells (1). But did you know that the same person consists of an estimated 100 trillion bacterial cells. That’s right, as a human we actually consist of 10 times more bacteria than what we do our own human cells! If an alien came down from outer space and analysed the composition of a human, they would describe us as a multicellular organism, consisting of mainly bacteria with about 10% human cells. These bacteria live in harmony with us on our skin, hair, respiratory membranes, vaginal membranes, etc but the vast majority populate our digestive system – especially the colon (a human’s ‘hindgut’). The purpose of these microbes is many fold and we still don’t fully understand all of the different types, strains and what these microbes are actually doing inside us. Not only do these bacteria break down our food, they manufacture certain essential vitamins, they keep ‘bad’ bacteria, pathogens and parasites at bay, and they drive our metabolism and the backbone of our immune system. So you and I are composed of 90% bacteria and quite literally, without them, we would succumb to illnesses and die.Multimillion pound research programmes are beginning to make some interesting finds, and you can read a lot more about that by googling ‘Microbiome Project’, ‘American Gut Project’ and ‘British Gut Project’. Did you know you can send off a sample of your poo and a swab of cheek cells from inside your mouth to the British Gut Project, and they will run an analysis to determine what are the main types of bacteria living inside your digestive system, a comparison with other people who have also sent samples, and some trends linking certain bacteria (or the lack of) to various diseases. (2) Now that’s amazing! Latest research is showing links between the bacteria living in your gut and obesity, metabolic syndrome, mental health problems, Parkinson’s, Alzheimer’s, autism, depression, asthma and many others. Research also shows that any change of diet will affect the bacteria in the gut, with some diets (such as a highly processed Western junk food diet) driving bacterial patterns that are associated with diabetes, metabolic syndrome and obesity, whilst other diets (such as healthy organic fruit and vegetables) driving an increase in our guts of the type of bacteria that are associated with lean, healthy, fit people. Eat healthily and you will have a healthy spread of gut microbes, but fall back into eating chemically processed, preservative laden, high sugar ready meals and within as little as ten days, your gut microbes reflect what you are eating – ie back to those strains associated with ill health and degenerative diseases.People who suffer from certain severe inflammatory bowel conditions have an increase in certain strains of bacteria (‘bad’ ones) and not enough of others (‘good’ ones). This imbalance is called dysbiosis. Some patients who have suffered years of gut pain, inflammation and diarrhoea have found no relief with medications, yet interestingly for over 90% of these patients, they can be cured by a technique called faecal transplantation. This is when healthy faeces, containing the full range of healthy bacteria from a healthy donor’s guts is passed via a tube to the colon of the patient with the inflammatory bowel disease. Yes, the patient has another person’s poo put inside their guts! Yuck! The results are remarkable – google faecal transplantation and read for yourself (3).So how does this relate to horses? Research into the horse microbiome has only just scratched the surface compared to human research but it is taking place with some interesting results. A healthy horse contains trillions of healthy ‘good’ bacteria and other microbes in their gut too. What percentage of a horse is horse cells and what percentage is bacterial cells has not been estimated as yet, but it is highly probable that a horse consists of much higher than 90% bacteria because of the type of digestive system they have, compared to a human. Horses are hindgut fermenters, relying on a massive fermentation vessel called the cecum (about two and a half black water buckets in size in a large horse) and this is full of microbes breaking down fibre, making vitamins, controlling the metabolism and innate immune system. Perhaps a horse is 95%, 99% bacterial cells with only a couple of percent as actual horse cells? What an amazing fact! Without a doubt, your horse is actually more bacteria than horse!Latest research in horses has shown certain types of bacterial strains found in their guts linked to laminitis, colic and other diseases (4). Here at Thunderbrook, our own in house research finds higher levels of certain types of bad bacteria linked to eating processed horse feeds with particular waste by product ingredients and pesticide residues. So, if we compare with our knowledge from human research, horses on healthy natural diets that they evolved to eat will most likely have a different pattern of bacterial strains living in their guts, compared to horses fed highly processed feeds and forages.So is it natural for a horse to eat other horse poo? Yes, it’s called coprophagy. When a foal is born its digestive tract is sterile – no bacteria are present. As the foal is being born, the placenta breaks and the foal’s environment is no longer sterile. It will pick up bacteria on its skin and ingest them too, as it passes through the mare’s vaginal canal. Then it will pick up even more bacteria from its mother’s skin as it takes its first suckle from her teats. If the foal has no bacteria in its guts, then it will have a very weak immune system – remember it’s the good bacteria in the guts that drive the metabolism and the immune system. So a foal is born with a hyper permeable intestinal membrane or ‘leaky gut’, which allows the large sized antibodies from the mare’s colostrum to pass through and enter the blood stream. Colostrum is the type of ‘milk’ produced initially by mothers which is rich in antibodies and other essential nutrients that the foal lacks. That is why foal’s are very prone to infections in their first few days, because their ‘leaky guts’ can let bad bacteria and toxins into the blood stream too – one of the causes of ‘joint ill’ in foals.Very quickly, the intestinal membrane cells that line the foal’s gut join together with desmosomes or ‘tight junctions’ that make the gut lining a strict, selective barrier, allowing only nutrients through. A foal now has to build up that community of good bacteria (with a smaller proportion of bad bacteria – there will always be some around) that will ferment the fibre in forage and feed, generate the nutrients, vitamins and play other essential roles such as controlling the immune system and metabolism. Studies in human babies show it takes up to three years for the correct balance of good bacteria to populate the human gut (5). That is why we don’t start to wean babies until they are six months old, a process that is done very gradually over many months with liquidised meals to start with. They simply don’t have the balance of good bacteria in the guts until that age to digest solid foods. Exactly the same is true of foals. It takes up to a year or longer for the foal to establish a balanced gut flora of healthy gut microbes. It does this by actively seeking out and eating its mother’s and other horses’ poo, over a period of months. Anyone who has bred a foal will know that they have a tendency to eat freshly dropped manure. The first 3 months the foal is heavily reliant on its mother’s milk, the next 3 months it has sufficient gut bacteria to begin to ‘creep’ onto feed and grazing, so that the earliest a foal should be weaned is probably around the age of 6 months or later. A foal eats other horses’ poo to establish the population of gut microbes essential for fermenting fibre, manufacturing vitamins, controlling its immune system and metabolism. It is one of the main ways of ingesting the correct balance of microbes into its gut.So why do adult horses sometimes take to eating other horses manure? Most likely for exactly the same reasons as why a foal eats manure too. If the hind gut has gone into dysbiosis and the balance of good bacteria to bad bacteria has been compromised, one of the quickest ways for a horse to correctly repopulate its hindgut is to ingest good bacteria in the right proportion. These living good microbes in the digestive tract are constantly reproducing in large numbers and emptied from the guts in the manure. Warm fresh manure from a healthy horse with no metabolic syndrome, laminitis, colic issues, etc contains hundreds of thousands of good live bacteria. Not just a single strain of yeast such as Yeasacc. Not just one or two strains of bacteria as in other probiotic supplements. Fresh healthy poo contains hundreds of thousands of live bacteria and other microbes, all in the correct balance, correct proportions as a horse requires. The vast majority of these bacteria can only survive outside of the guts for hours or a day at the most.By eating healthy poo, your horse is performing its very own ‘faecal transplantation’. However, this is nothing new. Wise horsemen of previous generations were well aware of this fact. My elders taught me how to feed probiotics to a horse well before expensive and very limited versions were sold on the market. It was known as ‘poo tea’. For a horse that was suspected of ulcers, inflammation of the digestive system, displayed regular colic, or had eaten excessive grain or rich grass or some other sudden change in diet, poo tea was made and fed. To make poo tea, a ball of fresh warm manure from a healthy horse with no suspected illnesses or worm burden was placed in muslin (or today use a nylon knee high stocking) and squeezed in a mug of cold water, until the water turned brown. The water, full of living good bacteria was fed to the colicky horse along with a dessertspoon of limestone flour, to buffer the stomach acid and allow the living bacteria to pass through to the hindgut. This was repeated twice a day for up to a week. The difference in many sick horses was amazing. It’s something we have practiced here with the Thunderbrook herd, as part of restoring their gut health. You can always check with your vet if you are unsure about this aged old practice that’s long forgotten by many. Horses sometimes eat other horses’ poo. I sometimes feed my horses other horses’ poo. Now you know why!© 2015. Dr Deborah Carley, Thunderbrook Equestrian.This article may be reproduced in full or in part, but must be credited to the original author above.