A prospective longitudinal study of diseases of lambs born in December and January and housed through to slaughter was carried out on three flocks (A, B and C) between 1989 and 1991. In the first year of the investigation (1989–90) three cohorts of approximately 80 lambs were examined in detail on a regular (weekly or fortnightly) basis. This involved over 2000 examinations and at least one clinical abnormality was observed in each lamb. In the second year (1990–1) the farmers were asked to present sick lambs for treatment on the farm. Farmers from flocks A and B participated in this part of the study; a total of 97/1295 lambs that were slaughtered received at least one treatment.

The carcases and visceral organs of lambs from each flock were observed after slaughter. There was no association between the abnormalities observed during routine examination of the cohort lambs (year 1) and those observed at post mortem meat inspection. However, in year 2, in lambs from flock A, there was a significant association between lambs treated for arthritis or pneumonia on the farm and the presence of arthritic or pleuritic lesions, respectively, post mortem. In both years of the study lambs which were older when slaughtered were significantly more likely to have pleuritic, pneumonic or arthritic lesions at meat inspection.

It was concluded that routine examination of groups of lambs is an inefficient and possibly ineffective method to identify lambs with lesions at slaughter. However, lambs which have been treated for disease, and the older lambs in a flock, had an increased prevalence of lesions post mortem and hence more detailed inspection of these animals would increase the efficiency of meat inspection.