Downgrading of lamb carcasses for overfatness is a major source of revenue loss to U.K. sheep farmers due to loss of EEC payments worth up to £20 per head. The difficulties of assessing fatness on live lambs by subjective assessment using lumbar palpation and the fact that in live markets the same techniques are used by the MLC graders cause problems to the farmer attempting to avoid overfat lambs. The trial reported here addresses the problem of how to feed lambs identified at live certification as overfat with the objective of reducing fatness but retaining the meat content of the carcass. Work by Hovell, Orskov, MacLeod and McDonald (1983) using intragastric infusion techniques showed how lambs could maintain positive N balance on diets that were below accepted maintenance levels for energy but had adequate protein.

In the first trial 76 Suffolk X overfat lambs previously fed on roots and concentrates outside were allocated to initial slaughter (28) or barley straw ad lib (24) versus barley straw ad lib + 100 g/day fishmeal pellets (24). Lambs were slaughtered after 14, 28 or 42 days on trial. Data was collected on the straw intake and liveweight change, but slaughter data was not available.