Gastrointestinal imbalances and injury are very common problems in the majority of horses. Horses that are stabled and trained are in a very different environment to the life styles of previous generations of horses, the occurrence of gastrointestinal problems has intensified in the last 20 years or so as the equine population and interest in sport/showing/performance breeding has risen. In the past horses would not have been exposed to periods of time galloping and jumping, long periods in the stable, long periods of travelling to events and long periods of time away from important members of the herd. Instead a large amount of this time would have been spend roaming in large groups to find food, this fresh supply of food would also contain other important nutrients known to maintain and support health.
Longer periods in the stable, limited food and daily training sessions, competing and travelling has created a need for extra support from the diet to maintain a normal healthy environment.
Gastrointestinal Health is a balancing act between internal protection and external agressive factors (see below)
Upper gastrointestinal tract integrity is dependent on a delicate balance between the naturally occurring protective factors –mucus and prostaglandins and the naturally occurring damaging factors hydrochloric acid from the digestive juices. Mucus and prostaglandin are provided from sufficient Omega 3 in the diet, though in today’s diet this vital nutrient may be lacking and in shorter supply than in previous times when grass and fodder were freely available.
In normal healthy freely grazing horse allowed to eat a variety of fresh fodder, the gut naturally produces a gastro protective substance called prostaglandin from the naturally occurring omega 3 fatty acids, found in many wild plants such as lingon berries and wild blueberries and other medicinal plants that wild horses would have access to.
The diagram below shows just how much consumption of omega 3 has fallen whilst the omega 6 consumption has risen, in past diets the ratios have been 1:2 but has recently been estimated at 1:25. This has created a shortage for the body to supply omega 3 for a wide range of natural occurring renewal processes.
One of the most important uses of omega 3 happen in the gut;-
The omega 3 fatty acids break down to eventually provide the gut with prostaglandins which are part of the healthy horse’s gastro-protective mechanism, which stimulate the production of mucus and also stimulate normal bicarbonate secretion and promote normal mucosal blood flow.
Good gut health depends primarily on the quality and thickness of the mucus lining and on the tightness of the barrier wall itself. When this is breached then the second line of defence is the epithelial wall and the maintenance of good nerve function and blood flow.
The gastric mucosal barrier is considered to be the main defence system, the barrier consists of the secretion of bicarbonates, mucus, phospholipids and immunoglobulins. The gastric epithelial barrier also represents part of the defence system that is remarkably resistant to acids and irritants and has the capability of rapid repair. The mucosal microcirculation together with the sensory nervous system defends the mucosal barrier. Sensing acidic diffusion into the gastric mucosa results in neural system mediated induced endogenous mediator release and hormone changes leading to an increase in mucosal blood flow which is a critical step in the renewal of normal balance.
The epithelial wall consists of ‘tight junctions’ which form a barrier, this barrier is also a gateway after the consumption of food to allow the maximum amounts of nutrients to flow over. This gateway can change size especially if the gut is overloaded by food and in times of normal stress or during intense exercise periods. Tight junctions are made from anchoring proteins (occludin) which are found and are naturally sourced from green leafy plants (spinach is a good example)
Luminal gastric protection
The mucosal- bicarbonate phospholipid barrier comprises the first line of mucosal defence. This barrier is formed of mucus bicarbonate and phospholipids. Mucus presents a layer that contains secreted bicarbonate and surfactant phospholipids. Mucus that acts as a physical barrier against luminal digestive enzymes, bicarbonate that maintains an almost neutral pH at the epithelial surface, together with the phospholipids of high hydrophobic properties can naturally protect against mucosal damage.
Mucosal surface is formed of a continuous layer of surface epithelial cells that secrete components of the mucosal barrier as well as naturally occurring endogenous protective mediators as prostaglandin. Basolateral membrane of epithelial parietal cells that secrete hydrochloric acid in high concentrations into the lumen of the stomach, contains transporters responsible for maintaining intracellular homeostasis.