Equine laminitis is a painful debilitating condition that seems to be a product of domestication of horses associated with the practice of feeding carbohydrate rich pasture in excess of requirements, particularly in ponies. We have been working on the hypothesis that caecal bacteria, when presented with carbohydrate in large quantities tend to ferment this. Fermentation by gram positive bacteria is associated with a fall in pH of the caecal liquor. As a means of providing themselves with increased intracellular buffering capacity, these bacteria produce amino acid decarboxylase enzymes which convert amino acids present in the caecal fluid into primary amines which can act as intracellular buffers. The reason we thought this might be the case was that foods formed by bacterial fermentation processes (e.g. cheese and wines) have a high content of amines. Primary amines derived from some amino acids have vasoactive properties. In the 1960s it was recognised that human patients taking drugs that inhibit the metabolism of amines (monoamine oxidase inhibitors) could suffer from severe hypertensive crises if they ate cheese or drank red wines with high tyramine content. This so called ‘cheese effect’ is the result of the indirect sympathomimetic effect of tyramine which displaces norepinephrine from sympathetic nerve endings leading to a rise in blood pressure. Monoamine oxidase enzymes present in the epithelial cells lining the gut wall and in liver cells normally protect individuals from suffering these hypertensive crises. We wondered whether amines released from the gut in response to ingestion of excessive amounts of carbohydrate might lead to a similar reaction in ponies whereby dietary amines caused vasoconstriction of the digital vasculature, leading to the prodromal phases of laminitis.