As this is a classic time of year for Laminitis, you may find this article from Dr Peter Bedding (Nutritional Consultant) of interest.
Laminitis, causes and effects.
Dr Peter. M. Bedding. Nutritional Consultant.
The condition of laminitis has baffled veterinarians for many years and many theories have been put forward as to the cause of this serious disease. Protein, sugars and toxins have all been suggested as causative agents, although protein, as a cause, has now been laid to rest. However we do know that a change in the hindgut pH towards acidity is without doubt a fundamental springboard to an imbalance of hindgut bacteria flora. This imbalance can be triggered by fructans in grasses and also by other water soluble carbohydrates (WSC’s) in hard feed. These, if undigested, reach the hindgut and sustain the proliferation of lactic acid producing bacteria, which changes the fermentation process and causes a drop in pH. This increase in acidity will negatively effect the permeability of the hindgut wall. Endotoxins, produced by the breakdown of dead bacteria, will then be able to penetrate the weakened gut wall and enter the bloodstream. These Endotoxins, in a number of studies, have been shown to effect the increased production of enzymes in the hoof. The enzymes concerned are called matrix metalloproteinases (MMP’s). They influence the attachment of the laminae, giving rise to inflammatory processes in the hoof. Another result of a disturbed fermentation process in the hindgut is the production of amines that are formed in the breakdown of proteins to amino acids. A number of these amines are actively vasoconstrictive and restrict the bloodflow through the blood vessels to the hoof. The overloading of the hindgut with an overflow of undigested WSC’s in the diet can cause serious effects of amine production and hemodynamic disturbances. It has been reported that, even during grazing, an increase of the amine content in blood plasma has been measured to such levels that are considered to be vasoconstrictive and could cause reduced bloodflow to the hoof, contributing to potential laminitic conditions.
Homocysteine, an amino acid, is also attributed to having a vasoconstrictive effect and has been researched in humans to be a possible cause of detrimental cardiac conditions. This is not proven in equines, but could potentially also have an adverse effect on bloodflow to hooves. The production of B vitamins in the hindgut fermentation process are necessary for the synthesis of enzymes that break down homocysteine. A disturbance in the fermentation process could reduce B vitamin production resulting in a reduction of these important vitamins. Inflammation in the hoof can furthermore be increased by pro-inflammatory enzymes or ingredients in the diet (technical metabolic description – Cyclooxygenase is released and catalyses the arachidonic acid released from the cell membrane into prostaglandins creating an inflammatory process). Nowadays it has become popular with feed manufacturers to add or recommend the addition of corn oil or other vegetable oils to increase the “slow energy” levels of feedstuffs. These oils are high in omega 6, which can be pro-inflammatory, so providing continuous large quantities or vegetable oil, on a daily basis, can cause muscle inflammation. The addition of antiinflammatory omega 3 (the ratio of omega 6:omega 3 is suggested as 4.5:1) will help to prevent a chronic condition of inflammation. It is therefore not unreasonable to expect the similar situation in laminitic conditions. Inflammation could be triggered by excesses of Omega 6 oils in the diet. Finally, because of the increased permeability of the gut wall, caused by the decrease in pH, it is possible that invasive antagonists will gain access to cell tissues. These antagonists could come from pathogens and mycotoxins found in feedstuffs and forage, thus a weakened gut membrane would make the horse or pony very vulnerable. The effects of poor feeding management and lack of specific nutritional support could increase the likelihood of toxins reaching bloodstream so leaving the animal prone to conditions like laminitis.