Population structure of a nucleus herd of Dorper sheep and inbreeding effects on growth, carcass, and reproductive traits

This study evaluated the pedigree structure of 3780 animals and assessed the inbreeding effect on the breeding values of body weight at 90 days (W90), longissimus muscle area (LMA), backfat thickness (BFT), and scrotal perimeter (SP) in a Dorper sheep flock. The pedigree completeness was 81.8% (1st generation), 56.6% (2nd generation), and 39% (3rd generation). The effective population sizes identified for complete, equivalent, and maximum generations were 83.07, 102.96, and 188.54, respectively. The flock included 62 effective founders and 57 effective ancestors, with 23 ancestors found responsible for 50% of the variability. The average inbreeding coefficient was 0.32%. The inbreeding effect was observed to be significant (P < 0.05) for LMA (0.0198 ± 0.0069) and BFT (0.0031 ± 0.0015). Thus, the pedigree under investigation showed reasonable completeness, but the generation interval (4.0 ± 1.7 years) needs to be decreased for the genetic gain per generation to be maximized. Moreover, in recent years there has been a dramatic reduction in effective population size (Ne) and increase in inbreeding in this flock, which can have consequences in the mid and long-term, although negative effects were not observed in the present study.