Cold stress and post-weaning diarrhoea in piglets inoculated orally or by aerosol

Three-week old piglets were subjected to two levels of moderate, chronic cold stress immediately post-weaning and inoculated orally or by aerosol with an enterotoxigenic strain ofEscherichia coli. Oral challenge, as well as both piglet-produced and artificial aerosols ofE. coliwere capable of inducing infection. In infected animals, live-weight gain and food conversion efficiency were significantly worse at 15°C than at 20° or 30°C. The incidence and severity of diarrhoea was greatest at 15°C and least at 30°C, but only in those piglets fedad libitum. Piglets fed at a restricted level kept at 15°C did not become infected or suffer a check in growth after inoculation. In the absence of other risk factors, piglets kept at thermoneutrality are unlikely to suffer post-weaning diarrhoea even in the presence of an enterotoxigenic strain ofE. coli. Diarrhoeic piglets did not exhibit the normal rise in food intake at temperatures below their thermoneutral zone. Traditionally, the design specification and control of the thermal environment in a piggery has been based on the performance of predominantly healthy pigs but the results of this study imply that the additional criterion of health can now be used.