Estimates of the genetic parameters of a Dorper flock in Brazil

Dorper sheep breeding increased in several countries but the estimates of genetic parameters for some traits remain unknown. Therefore, this study aimed to estimate genetic parameters for body weights at birth (BW), 30 (W30), 60 (W60) and 90 (W90) days of age, total and daily weight gains from 0 to 30 (WG1 and DWG1), 30 to 60 (WG2 and DWG2) and 60 to 90 days (WG3 and DWG3), Longissimus muscle area (LMA) and backfat thickness (BFT) measured by ultrasound between 12th and 13th ribs, and scrotal perimeter (SP) in the Dorper sheep breed using REML. The database analyzed involved 3131 sheep, of which were 1697 females and 1434 males. The assessments of direct heritability for weight and weight gain were normally found to be low, showing moderate values for W90 (0.21 +/- 0.04) and WG3 (0.23 +/- 0.06) alone. The heritabilities estimates for LMA, BFT and SP were 0.07 +/- 0.03, 0.10 +/- 0.05 and 0.34 +/- 0.07, respectively. Positive and generally high genetic correlations were observed between the weight and weight gain variables, but the correlations between total and daily gains showed some variations, and in certain cases they approached zero. While the genetic correlation between LMA and EFT was 0.76 +/- 0.13, both revealed high genetic correlation with DWG3. The scrotal perimeter also showed high genetic correlation with DWG3 (0.72 +/- 0.10). In conclusion, the W90, WG3 and SP are appropriate selection criteria for Dorper sheep improvement. The LMA and BFT however, show a lower potential for genetic gains with the selection, as they exhibited low heritability, but they can serve as reliable selection criteria because they are related to sheep carcass quality.