An experiment was carried out at the Glensaugh research station to investigate the effects of breeds of ewe, differing in mature body size on the utilisation of a long-established reseed maintained at sward heights of 3.5 and S.5 cm until weaning.

The experimental area, dominated by Lolium perenne (40%), Poa spp (30%) with other grasses (10%) and weed species (20%), was divided into 12 plots each of 0.7 ha. When the mean sward height reached at least 3.5 cm in every plot (13.5.85) they were each stocked with 9 ewes + 15 lambs from one of 3 ewe genotypes (Border Leicester x Blackface, GF; East Friesland x Blackface, EFX; Cheviot x Shetland, SHX) in two replicates. All lambs were sired by Suffolk rams.

Mean sward height, herbage mass and estimated herbage accumulation rate were measured weekly and ewes and lambs were weighed weekly. Sward heights were maintained on each plot by movement of an electric fence to vary the grazing area. The area behind the fence was maintained at an equal sward height by non-experimental ewes and lambs to permit movement in any direction. The lambs were approximately 6 weeks old at the beginning of the trial and were weaned after 13 weeks on the plots.