Rain and windchill as factors in the occurrence of pneumonia in sheep.

A computerised information retrieval system of abattoir pathology and meteorological data has been used to investigate the effect of prevailing weather conditions on the occurrence of pleurisy and pneumonia in the sheep population of Northern Ireland. Significant correlation coefficients were found between the percentage condemnations due to pleurisy and pneumonia in sheep and rainfall, windspeed, temperature and humidity. The most significant correlation was found with windspeed. The paper describes the calculation of a new meteorological variable, the rain/windchill factor. Very highly significant correlation coefficients were found between the percentage lung condemnations in sheep and the rain/windchill factor prevailing during the same month and both one and two months previously. The paper discusses the practical implications of these findings for sheep production and highlights the desirability of protecting sheep from adverse climatic conditions during the winter months.