Estimation of genetic parameters and genetic gains for reproductive traits and body weight of D'man ewes

The current study consisted of genetic analysis for reproductive performance and body weight using from 2003 to 2863 records of 1018 D'man ewes born from 136 sires and 468 dams. Data were collected from 1988 till 2009 in the Errachidia Experimental Station (ESE) of the Institut National de la Recherche Agronomique. Conception rate (CR), litter size at birth (LSB), litter size at weaning (LSW), litter weight at birth (LWB), litter weight at weaning (LWW), gestation length (GL) and ewe's body weight (EBW) averaged 94.4%, 2.38 lambs, 2.03 lambs, 6.23 kg, 39.6 kg, 149.9 days and 44.8 kg, respectively. The analysis of variance showed that LWB and EBW were influenced by age of ewe, parity and period of lambing. Also, period of lambing had significant effects on all studied traits. However, age of the ewe did not affect LSB and LWW. Genetic parameters and genetic trends for reproductive traits and EBW, estimated through REML and BLUP procedures using a repeatability animal model including additive genetic and permanent environment effects, in addition to fixed effects, resulted in heritability estimates of 0.09, 0.11, 0.10, 0.10, 0, 0.22 and 0.44 and repeatability estimates of 0.19, 0.13, 0.16, 0.10, 0, 0.26 and 0.62 for LSB, LSW, LWB, LWW, CR, GL and EBW, respectively. Genetic correlations among traits ranged from −0.21 and 0.93 and phenotypic correlations varied from −0.07 to 0.82. Estimated annual genetic progress was very small; 0.0009 lambs for LSB and −0.0078 kg for EBW. The study concluded that the actual genetic parameter estimates could be used in a breeding program to improve the productivity of D'man ewes and to make significant genetic progress.