Suspected primary lactose intolerance in neonatal foals

The intestine of neonatal mammals must be able to secrete lactase enzyme to hydrolyse lactose in its mother's milk. Failure to secrete lactase results in failure to digest lactose. This results in osmotic diarrhoea, weight loss, failure to thrive, lethargy, colic and abdominal distension. Lactose intolerance may occur secondarily to intestinal bacterial infection. Primary lactose intolerance is recognised in human infants. Here we report 2 cases of suspected primary lactose intolerance in foals. The foals responded well to oral administration of exogenous lactase enzyme.