Foal Heat Scours and Diarrhoea

‘Foaling Heat Scours’ is one of the most common types of scours to affect foals. Yet the name is a bit of a misnomer, and often leads to confusion as to the actual cause of this form of diarrhoea.

This yellowish, greenish, watery scour generally occurs in foals around 7-14 days of age, hence often coinciding when a mare comes into foaling heat. We know however, that orphan foals and foals reared in isolation from mares commonly develop this characteristic type of scours: thereby indicating that mare hormonal fluctuations alone do not drive their development.

This type of diarrhoea is more accurately attributed to the changes occurring in the developing hindgut of the foal. Foals of this age are starting to consume grass (having initially relied entirely on nursing milk from their dams). The proper digestion of grass requires the actions of specific microbes in the hindgut. Foals aren’t born with these microbes- they establish themselves upon exposure to feed and various environmental conditions.

Until the microbial population is well established and digestive enzyme secretion normalises in the foal, the fibre from grass remains largely undigested. The result? Yellowish, greenish scours which often contain visible clumps of undigested grass.

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