Calf diarrhoea in the first three to four weeks of a calf’s life is the leading cause of calf mortality and economic loss for producers of beef and dairy calves (and has been for quite a number of years) in Ireland, according to Department of Agriculture, Food and the Marine statistics. The costs of treatment or indeed preventive medicines are compounded by a list of other economic losses. These include reduced growth or production in later life, delayed development of affected calves, increased labour costs, the cost of dead calves, lost income from the potential sale of heifers that now have to be retained, a reduction in the rate of genetic improvement, and an increased risk of chemical residues in calves.