Estimation of breed effects and non-additive genetic variation for ostrich slaughter and skin traits

The study quantified breed effects and putative non-additive genetic variation for quantitative and qualitative slaughter and skin traits involving three ostrich breeds: South African Black (SAB), Zimbabwean Blue (ZB), and Kenyan Red (KR) ostriches. Such data from contemporary slaughter groups with all three pure breeds represented were analyzed together (SAB: n = 457; ZB: n = 74; KR: n = 50). Two 2 × 2 diallel crossbreeding designs were used to assess crosses of ZB and KR birds with the SAB strain. Subsequently, the data from SAB, ZB and their reciprocal crosses, slaughtered together; as well as the data from SAB and KR ostriches, along with their reciprocal crosses, respectively, were analyzed separately. ZB and KR birds outperformed SAB birds for most size-related slaughter and skin traits. Linear contrasts were used to distinguish the effects of breed, heterosis, and the dam line. For the ZB x SAB design, additive breed effects were significant for slaughter weight (10.4%), crust skin size (3.9%) and nodule shape score (1.6%) (all P < 0.05). Significant heterosis were found for slaughter weight (4.3%), crust skin size (1.7%) and nodule size score (3.7%) (P < 0.05). Dam line effects were observed for skin weight (4.1%) and hair follicle score (4.1%). In the KR x SAB design, additive breed effects were like outcomes for the ZB x SAB design. Heterosis estimates were significant (P < 0.05) for slaughter weight (5.8%), crust skin size (2.9%), crown length (1.7%) and nodule size score (4.4%). Dam line effects were significant for slaughter weight (3.7%) and nodule size score (3.8%). In conclusion, ZB and KR birds outperformed their SAB contemporaries for size and size-related traits. Crossbreeding with these genotypes could improve some size-related traits over the mid-parent value of purebreds.