Experimental studies of chronic pneumonia of sheep

Strains of Mycoplasma ovipneumoniae and Pasteurella haemolytica isolated from sheep affected with chronic pneumonia were inoculated by endobronchial route to conventionally-reared and SPF (Specific Pathogen-Free) lambs. Changes resembling those of the naturally-occurring disease were produced in most lambs given the organisms in combination and in some given M. ovipneumoniae alone. Similar but less extensive changes were seen in SPF lambs and fewer animals were affected. Different strains of M. ovipneumoniae did not affect the extent of changes produced in SPF lambs. M. ovipneumoniae became established in the lungs of both types of sheep; P. haemolytica did so less readily.

It was concluded that chronic pneumonia may be reproduced in conventional animals by combined inoculation of M. ovipneumoniae and P. haemolytica. Age and status of immunity to mycoplasmas may account for the different responses of conventional and SPF lambs.     

Some effects of copper deficiency on leucocyte function in sheep and cattle

Peripheral blood leucocytes from copper-deficient (less than 8 mumol per litre plasma) and copper-sufficient (more than 8 mumol per litre) ewes and lambs were tested for their ability to ingest and kill Candida albicans in vitro. Killing capacity was significantly reduced in both copper-deficient ewes and lambs, although phagocytic capacity was apparently unimpaired. Similar results were obtained with copper-deficient calves, in which it was further shown that copper repletion restored candidacidal activity. Leucocyte and erythrocyte superoxide dismutase (LSOD and ESOD respectively) activities were both significantly decreased in hypocupraemic ewes and there was a linear relationship between their activities in the two cell types: LSOD activities were reduced by approximately 35 per cent and ESOD activities by 67 per cent. Cyanide inhibition tests indicated that the manganese-dependent form of the enzyme contributed little to the total activity of LSOD or ESOD. There was a tendency for leucocytes from copper-deficient ewes to release greater amounts of superoxide anion after stimulation with opsonised zymosan. Their viability was similar to that of leucocytes from control sheep and was unaffected for up to three hours after stimulation.