The causes

Acute diarrhoea can be caused by a change in your horse’s routine — for example, if a new food is introduced, or a medication, such as an antibiotic or worming treatment, is given. A sudden change in diet, or an oral medication, can change the gut microflora (friendly bacteria), leading to an overgrowth of unwanted bacteria in the intestine.

Some horses show signs of diarrhoea when they are travelling, which is usually the result of a stress response. More serious causes of acute diarrhoea include salmonella infection, eating toxic plants and peritonitis (inflammation of the membrane lining the abdominal cavity). Chronic diarrhoea can follow on from acute diarrhoea, or may present as periods of normal faeces interspersed with episodes of diarrhoea. Causes of chronic diarrhoea include worms, bacterial infection, inflammatory bowel disease, ulceration and intestinal cancer. In both acute and chronic diarrhoea,

the initial cause results in damage to the intestinal wall, so the intestine can’t absorb water in the usual way. Water remains inside the intestine, giving the faeces a watery consistency. Inflammation in the intestine can also cause an increase in the transit time — the time it takes for food to get from one end of the horse to the other. When the intestinal wall becomes damaged, it cannot absorb the usual nutrients from food, so your horse may lose weight, especially if the diarrhoea persists for a longer period of time.

A foal’s immune system is not as well developed as that of an adult horse, so foals can pick up infections more easily and become sicker more quickly. At around seven days old, foal heat diarrhoea can occur. This is usually nothing to worry about as the foal is usually bright, feeding well and not showing other signs of illness. If a foal shows signs of systemic disease, such as a high temperature, reluctance to feed, or is looking quiet or depressed, then advice from a vet should be sought immediately to prevent deterioration.