In the spring, at the beginning of the grazing season, it is always wise to start grazing quietly. Your horse's intestines and digestive system must first adapt to eating grass before your horse can go out in the pasture for whole days. There is also the risk of laminitis. For some horses, this danger persists throughout the grazing season. How come? What does grass do in your horse's body? And which horses are at increased risk of laminitis?
Grass is the tastiest thing for most horses. The whole day snacking through the meadow; you can do them no greater pleasure. However, it is not always healthy. This is due to the way in which the sugars from the grass are processed in the horse's body.
Sugar metabolism: fast and complex carbohydrates
Grass is the main source of carbohydrates for many horses during the grazing season. Carbohydrates can be divided into complex carbohydrates and carbohydrates that are water-soluble. The latter are the 'fast sugars' and starch, which can also be found in concentrates, for example. These water-soluble carbohydrates are broken down by enzymes in the stomach and small intestine and immediately provide a lot of energy. When the breakdown of soluble carbohydrates does not take place completely in the first part of the digestive tract, sugar and starch end up in the large intestine. There, these substances can disrupt the intestinal flora and cause gas colic. Because a horse only has a limited capacity to digest sugars quickly in the stomach and small intestine, the feed (and therefore also the grass) should not contain too many water-soluble carbohydrates. If a lot of sugar suddenly enters your horse's blood, it can cause laminitis.
As grass grows older, has more length and has finished flowering, it contains more fiber. Fiber consists of complex carbohydrates such as cellulose. The horse cannot digest such carbohydrates independently, for that he needs the micro-organisms in his large intestine. These bacteria and fungi convert the cellulose fibers into volatile fatty acids. The horse can then absorb these fatty acids and convert them into energy. When there is too little fiber in a horse's diet, the digestive system cannot function properly. The large intestine is then not sufficiently active, which can cause various digestive problems and diseases in the horse. A horse therefore has a rather special digestive system. You call this 'hindgut fermenting': the most important part of food processing takes place through fermentation in the back part of the gastrointestinal tract. To keep a horse healthy, you have to take this special digestive system into account.
New insights into laminitis
In the past, laminitis was often seen as one separate condition, but there appear to be different forms of this disease. All these forms are in fact systemic diseases, involving the whole body of the horse. So it is certainly not just a problem in the hooves! Causes of laminitis can be: endocrine diseases (hormone-related), blood poisoning (sepsis), a generalized inflammatory reaction (Systemic Inflammatory Response Syndrome (SIRS)), or a unilateral load on one leg (for example by plaster after a fracture). In addition, laminitis as a result of an endocrine (hormonal) problem is the most common. The traditional view that laminitis mainly occurs when the lamellae come off the hoof also appears not to be entirely correct. It seems that there is a rather variable, poorly visible, preliminary phase. In addition, there are already changes in the structure of the dermis. Research shows it starts with microscopic changes. Certain lamellae become stretched and the structure of the dermis changes. This causes inflammation in the cells.
The link between sugars and laminitis
The endocrine problems that can cause laminitis have to do with the horse's sugar metabolism. If there are sugars in a horse's blood, the hormone insulin is released to process these sugars. The more 'fast sugars' in the blood, the more insulin. The tiny capillaries in the dermis of the horse's hoof are very sensitive to this insulin and will contract if there is a lot of insulin in the blood. The blood circulation in the hoof is then less good. This hinders the healthy growth of the dermis and inflammation and laminitis are then lurking. This association with insulin is also the reason that horses with IR (Insulin Resistance), PPID (Cushing) and EMS (Equine Metabolic Syndrome) are more at risk of laminitis. Their insulin levels are often disturbed. Even with a mild disturbance of the insulin level, sensitivity in the hooves can probably already occur.
Sugar in grass: a lot of difference
To prevent your horse from getting laminitis, it is therefore wise not to feed too much sugar (starch). Especially if your horse is already a bit too fat or has IR, PPID or EMS. Cold-blooded horses are also often extra sensitive. Grass can contain a lot of sugar, but it doesn't have to be. That depends, among other things, on the time of year, the weather, the length of the grass and the type of grass with which the meadow is sown. The highest sugar levels are found in high-yielding 'cow grass' such as perennial ryegrass. Overgrown, overblown, fiber-rich 'horse grass' - which is available in special seed mixtures - contains less sugars. But even then you have to pay attention. Hay also contains sugar, so take your horse's total ration into account. You can have both grass and hay tested at specialized companies. That way you can steer better. Keep in mind that horses that only graze a few hours a day often eat much faster and can therefore still get quite a lot of sugar!
Got too much sugar?
Has your horse ingested too many sugars and do you want to support him in regulating his insulin level and preventing inflammation? Then you can, for example, do a mild detox with nettle extract. In this way waste materials are removed faster. In addition, you can support the balance in the horse's body with cannabinoids. These plant substances also have an analgesic and anti-inflammatory effect.
Asplin KE, Patterson-Kane JC, Sillence MN, Pollitt CC, Mc Gowan CM. Histopathology of insulin-induced laminitis in ponies. Equine Vet J. 2010 Nov;42(8):700-6. doi: 10.1111/j.2042-3306.2010.00111.x. PMID: 21039799.
Patterson-Kane JC, Karikoski NP, McGowan CM. Paradigm shifts in understanding equine laminitis. Vet J. 2018 Jan;231:33-40. doi: 10.1016/j.tvjl.2017.11.011. Epub 2017 Nov 22. PMID: 29429485.