| Abstrakt: |
The aim of present research was to estimate genetic parameters and trends of prolificacy traits in Afshari sheep breed under the FecB gene introgression breeding program. In this research, phenotypic data were collected from 2000 to 2015 at the Research Station of University of Zanjan. The reproductive traits include the total number of lambs born (NLB) and number of lambs at weaning (NLW), and composite traits as total litter weight at birth (TLWB) and total ltter weight at weaning (TLWW). The data were analysed using ASReml software according to restricted maximum likelihood (REML) procedure. The fixed model effects parameters were: year, season, age of ewe. Results showed genetic group and number of parturition in the model were significant (P<0.05). The direct heritability estimates for NLB, NLW, TLWB and TLWW were 0.08, 0.08, 0.12 and 0.12, before gene introgression and 0.07, 0.10, 0.08 and 0.12 after gene introgression, respectively. The genetic trend of NLB, TLWB, TLWW and NLW from 2000 to 2006 (before gene introgression) were 0.003 ± 0.002 lambs/year, 0.0005 ± 0.003 g/year, 0.010 ± 0.002 g/year and 0.0003 ± 0.003 lambs/year, respectively and 0.055 ± 0.003 lambs/year, 0.04 ± 0.002 g/year, 0.026 ± 0.004 g/year and 0.005 ± 0.005 lambs/year, respectively from 2007 to 2015 (after gene introgressions cheme). Because of gene introgression breeding scheme implementation and parturition of gene carrying ewes in this research station from 2007 to 2015, the genetic trend was positive with a few fluctuations. The results showed that the insertion and stabilization of the FecB gene caused a significant different in the genetic trend of the prolificacy traits. These results suggest that breeding strategy based on transfer major genes such as FecB and cross breeding for genetic improvement of reproduction efficiency is more effective than the classic phenotypic selection. [ABSTRACT FROM AUTHOR] |
