Influence of a 12.5 per cent rapeseed diet and an avian reovirus on the production of leg abnormalities in male broiler chickens.

The incidence of different forms of leg abnormality were recorded in reovirus (S1133) infected and control male broiler chickens fed on a normal commercial diet or one of similar nutritive value containing 12.5 per cent rapeseed meal. Regular serological examination showed that birds remained free from Mycoplasma gallisepticum and M synoviae infection throughout the 10 week period of investigation. Precipitating antibodies to the reovirus were detected in 90 per cent of the infected birds between the third and 10th week after infection. Carotene levels in rapeseed fed groups showed no significant differences between reovirus infected and control birds or between birds with or without clinical signs of leg abnormality. The most frequent and severe leg abnormalities were present in the infected birds fed on the rapeseed diet, followed by those fed on the normal commercial diet. There was a highly significant difference (P less than 0.01) between the number of birds with leg abnormalities in each of these groups and their corresponding control groups. The lesions which were mainly responsible for these differences were tenosynovitis and enlarged hocks. Oral infection with reovirus did not appear to make the birds more susceptible to other types of leg abnormality, although the severest lesions of dyschondroplasia were seen in birds which had been exposed to the dual effects of reovirus and rapeseed diet.