Growth and carcass composition in the crossbred progeny of six terminal sire breeds of sheep

Abstract

Records were available for the progeny of Dorset Down, Oxford, Suffolk, Ile-de-France, Oldenburg and Texel sires out of Border Leicester × Blackface and Animal Breeding Research Organisation Dam Line × Blackface ewes. The data analysed were: (a) growth traits to 12 weeks for 2585 lambs, the progeny of 102 sires; (b) growth traits for slaughter at fixed weights of 35kg and 40kg for 1884 lambs (79 sires); and (c) half carcass dissection traits for 956 lambs (65 sires). Oxford and Suffolk cross lambs were heaviest at all ages and thus youngest at slaughter. Texel cross lambs grew slowly to 12 weeks but were not significantly older than Dorset Down, Ile-de-France and Oldenburg cross lambs at slaughter. The Texel cross produced the leanest carcass with a high lean/bone ratio and eye-muscle area. Dorset Down and Ile-de-France cross lambs were fattest at slaughter but had high values for lean/bone ratio and eye-muscle area. Interactions between breed of sire and slaughter weight were non-significant for all traits (P>0·05). Breed differences in carcass composition were also compared statistically as if at a constant percentage of subcutaneous fat. The differences were not so great as at constant live weight but the Texel cross would have had the leanest carcass. Side weights would be heaviest in the Texel and lowest in the Dorset Down and Ile-de-France. Oxford, Suffolk and Dorset Down cross lambs would be youngest at slaughter and Texel and Oldenburg crosses oldest.