Effects of Dam and Sire Breeds on Lamb Carcass Quality and Composition in Pasture-Based Systems.

This study explored the impacts of sire and dam breed on carcass quality and composition in a pasture-based system and the use of DXA to rapidly rank carcasses for leanness. Southdown (SD) and Suffolk (SF) ewes were mated to Texel (TX) or SD rams to produce seventy-nine lambs. Lambs were raised on pasture-based systems with limited grain supplementation. Lamb birth weight was greater ( < 0.01) for TX, regardless of dam breed. Lambing rate was lower ( < 0.01) for SD than SF ewes. Circulating myostatin concentrations were greater ( < 0.05) on d 42 than d 75 or d 110 but did not differ by sire breed. Texel-sired lambs had greater ( < 0.01) carcass weight, ribeye area and quality grade compared to SD-sired. Total and primal fat mass as predicted from DXA was higher ( < 0.05) in carcasses from SD than TX sires. Muscles from TX lambs had greater ( < 0.05) polyunsaturated fatty acid (PUFA) composition than SD-sired. Shear force values were influenced ( < 0.01) by dam breed, muscle cut and postmortem age but not by sire breed. The use of TX sires in pasture-based systems improved carcass leanness and muscle PUFA concentrations without altering tenderness.