Both level of feeding and dietary composition have been demonstrated to influence bacterial colonisation and diarrhoea in the weaned pig. Specifically, Bertschinger et al (1979) demonstrated that diets low in protein and energy and high in fibre content could protect the weaned pig against challenge with live pathogenic E. coli. However, pig growth was so compromised that it proved to be unsatisfactory for commercial practice. Miller et al (1984) demonstrated that a diet in which the protein (casein) had been hydrolysed to constituent amino acids or peptides, thus markedly reducing its antigenicity, also could prevent post-weaning diarrhoea and minimise associated gut changes. They therefore, suggeted that one of the factors which may contribute to the aetiology of post-weaning diarrhoea is a transient hypersensitivity to dietary antigens prior to tolerance development.

The aim of this present work was to attempt to combine these two approaches yet achieve acceptable piglet performance, the long-term aim being to design weaner diets which effectively control post-weaning diarrhoea on commercial farms without resulting in the use of antibiotics either prophylactically or therapeutically.