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

SIMPLE SUMMARY: This research examined the use Texel or Southdown sires on Southdown or Suffolk dams to improve carcass quality and muscle composition in lambs produced on pasture-based systems. Texel-sired lambs had heavier carcasses, larger ribeye areas and individual muscle weights from the loin and leg. Dual energy X-ray absorptiometry was used to rapidly rank carcasses for leanness by dam and sire breeds. Texel-sired lambs had lower, more desirable, rank for carcass leanness and less total carcass fat. Individual muscles of the loin and leg from the various breed combinations were evaluated for fatty acid composition and tenderness. Dam and sire breed influenced fatty acid composition of the muscles. The semitendinosus muscle had the highest total fatty acid content and lowest ratio of n-6 to n-3 fatty acids. Overall, muscles from these lambs finished on pasture with limited grain supplementation were very lean, with high concentrations of polyunsaturated fatty acids and a ratio of n-6 to n-3 fatty acid of below 4:1, which is considered beneficial for human health and reduction of coronary heart disease. The use of Texel sires in pasture-based systems improved carcass leanness and muscle PUFA concentrations without altering tenderness. ABSTRACT: 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 (p < 0.01) for TX, regardless of dam breed. Lambing rate was lower (p < 0.01) for SD than SF ewes. Circulating myostatin concentrations were greater (p < 0.05) on d 42 than d 75 or d 110 but did not differ by sire breed. Texel-sired lambs had greater (p < 0.01) carcass weight, ribeye area and quality grade compared to SD-sired. Total and primal fat mass as predicted from DXA was higher (p < 0.05) in carcasses from SD than TX sires. Muscles from TX lambs had greater (p < 0.05) polyunsaturated fatty acid (PUFA) composition than SD-sired. Shear force values were influenced (p < 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.