The horse’s digestive system can be split into the foregut, including the stomach and small intestines and then onto the hindgut, which comprises of the cecum, large colon and the small colon, rectum, and anus. The food eaten by the horse is digested differently in these two regions. In the foregut digestion is primarily driven by enzymes, breaking down fats, proteins, and simple carbohydrates such as sugar and starch. Whereas, as the horse’s digestive system moves from the foregut to the hindgut, it switches from being driven by enzyme to being driven by microbes.
Microbes include populations of different types of bacteria and other micro-organisms called protozoa, collectively these are sometimes referred to as the ‘gut biome’. It is this biome that is responsible for converting fibre from the diet into energy for the horse, by a process of fermentation. Fibre should comprise the largest nutrient in any horse’s diet, and as such the presence of a healthy population of these micro-organisms is essential for a horse’s overall health and performance. In fact, disruptions in the hindgut biome have been shown to increase the risk of diseases such as hindgut acidosis, excessive weight loss, reduced appetite, and even colic and laminitis, to name but a few. There are multiple factors that can challenge the health of the hindgut biome, and unfortunately winter often sees an increase in several of these.
The colder months with reduced day light can be challenging for horses and their hindgut. Required changes to horse management can all potentially negatively impact the gut biome, but with careful consideration and preparation these risks can be limited. The bacteria and protozoa populations within the hindgut have adapted over time to that horse’s current diet. Any rapid changes can cause a disturbance in the gut biome, and if significant enough this can result in lactic acid production, the death of groups of healthy bacteria, and the production of toxins within the hindgut, and also inflammation and reduced integrity of the gut wall.
As the grass stops growing and the mud returns with a vengeance it is likely that a horse will either need to be changed to ‘winter’ turnout fields and also need to be supplemented with preserved forages such as hay or haylage. Fibre such as grass, hay or haylage are critical for the digestive and mental health of horses, and should form the largest part of their daily feed ration. The minimum amount of fibre required by a horse is 2% of its body weight per day, this weight is based on a dry matter basis. This explains why it is necessary to feed more haylage than hay and far more grass than any dried forage due to their higher water content. The choice of which dried forage can be depicted by availability, storage ability on a yard, cost as well as palatability. The key importance is the correct provision, ensuring the minimum amount is given, but in the case of the ‘good doer’ it isn’t fed in excess. It is also important that it is fed in a manner that prevents periods of four plus hours without any fibre source being available, this is where small, holed nets can be useful. To ensure hindgut health changes to the fibre source should be done gradually over at least a two-week period. This could include introducing the dry forage in stages before it is actually essential and turning out into the ‘winter field’ set up in gradually increasing intervals over a transition period. This will allow the gut biome to adapt to the new forage and reduce the risk of disturbances.
For many horses winter means an increased time stabled, which intern increases dried fibre sources to a higher proportion or even to being the sole source of fibre in the diet. Again, for hindgut health changes to the type or amount of fibre should be done in stages and over a two-week period. This could be achieved by increasing the time stabled in stages rather than as a single change from summer to winter management. Stabling also reduces the horse’s movement, which can reduce the mobility of the digestive system. Providing the hay or haylage in a single point in the stable can exacerbate this and reduce movement further. Splitting the hay or haylage and providing it in two separate points in the stable can increase the horse’s movement and reduce the speed at which it is eaten.
Winter & hard feed
Considering how your horse’s workload or body condition is likely to change over winter can be a great exercise to consider if changes to the energy content of their hard feed they will be need. If the work load (intensity, duration, or frequency) is likely to reduce, compared with the summer it may be appropriate to reduce the energy fed in their bucket feed. This is also the case with those who have gained too much summer weight and need to safely loose over the winter. However, be mindful that if the hard feed is likely to need to be reduced below that of the minimum feeding rate as stated on the bag, the provision of vitamins and minerals would be under provided. In this situation it is advisable to change to a lower energy (MJ/kg) feed that would allow for appropriate feeding rates or even to change to a low intake feed such as a balancer. Considering changes before they are essential will allow for the scope to employ a transition period, which in the case of hard feeds should take at least one week to change over or to introduce a new feed.
Not all horses will see a reduction in their workload over the winter months, and for some such as performance horses competing thought out the winter, their workload may even increase. For these individuals and for those who tend to drop weight excessively through the colder months it is probable that they will require extra energy or calories than just those from their fibre provision. The choice of an appropriate hard feed formulated for the correct work level e.g., a product within a performance range can provide the extra calories and elevated vitamins and minerals for the harder working horse. Alternatively conditioning feeds, typically higher in oils, can support weight maintenance in colder temperatures. Again planning ahead will allow the time and scope for a transition period, avoiding sudden changes to the diet. Avoiding the risks associated with disturbances in the hindgut. In both these situations care should be taken to avoid exceeding the stated feeding rates, as by doing so could provide some nutrients in excess of what is optimal. It is also advisable to ensure the weight of each bucket feed does not exceed 2kg, as this would reduce digestibility. As well as creating the risk of starch and sugars reaching the bacteria in the hindgut, which could result in rapid detrimental changes to the biome. Where a bucket feeds exceeds 2kg it should be divided down into a larger number of meals throughout the day till each feed falls below this maximum weight.
A further winter risk comes from the feed room, and I often hear the phrase “Oh I still have some of that left over”. Unfinished bags of feeds that have become damp or damaged or even ones that have been opened and stored in bins since the summer shouldn’t be fed. Incorrect or excessive storage periods increase the risk of moulds developing, which then create toxins that can negatively impact a horse’s digestive system and overall health. The potential of saving a few pounds on unsuitable feed is just not in my professional opinion worth the risk.
Rugging and the Hindgut
The choice of what rug is suitable seams to a (mind the pun) hot topic every winter. Horses working to a level where they sweat are likely to require their winter coats to be partially or completely clipped for management ease and to prevent sweaty horses getting too cold following exercise. The removal of their hair and natural means of insulation means they will probably require a rug in colder temperatures. If unclipped, and healthy with a good body coverage and sufficient fibre, they are unlikely to require insulation, and more often than not just protection from the wind and rain.
Horses have a much wider thermoneutral zone than we do. An unclipped horse in good condition with access to fibre is unlikely to burn a calorie maintaining body condition until its temperatures drop below 5C. This is because of the action of the bacteria in the horse’s hindgut. As the bacteria breakdown or ferment the fibre they produce significant levels of heat, acting like an internal radiator. Once rugged if required, a horse should just feel warm and not hot to the touch. If a horse is over rugged, where it becomes hot, it negatively impacts the hindgut. The heat generated by the bacteria is prevented from escaping and builds up, causing changes to the biome and can result in reduced apatite, poor performance and even cause colic. But each horse is an individual and monitoring rug choice, and the forecast temperatures is advisable.
Water and winter
Winter poses a further challenge for horses and their hindgut. As temperatures drop below 7C many horses will reduce their water intake, a major contributing factor as to why compaction colic’s are more frequent in winter. As water passes along the horse’s digestive system it is absorbed into the blood stream via the hindgut. If the amount of water present in the gut is reduced the movement through the hindgut slows, too much water is then removed, which can result in hard dry faeces or even a compaction. Monitoring water intake can alert you to an issue early, ensuring sufficient fibre in the diet and increasing the water content of bucket feeds with the use of Soakable fibres can all help to ensure sufficient water intake during those colder temperatures.
Supporting the Hindgut
Winter is a challenging time for owners, horses, and their hindgut. By considering and planning for likely dietary changes, monitoring water intake and choice of rugs, the impact of these challenges can be limited. But with so many challenges present it may also be worth considering and investing in a hindgut supportive supplement of pre or pro biotics. These supplements focus on protecting and supporting the vital bacteria populations within the gut and assisting them to cope and adapted to changes.