الفهرس 
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Abstract
This investigation was carried out to estimate variance component (heritability and genetic correlation mainly), to investigate and construct sex selection indices to choose the more efficient index to use for evaluation and ranking ewes.
Data used in the present study were collected from Mallawy (south Egypt) experimental station belonging to the Ministry of Agriculture during the period from 1994 to 2010. The total available number of Farafra ewes and lambs in the present study was 837 and 1158, respectively. Mallawy station followed the system of three lambing per two years in the entire period.
The traits were used in this study were weaning and yearling weight (WW and YW, respectively) as a growth traits; and number of lamb born and weaned and kilograms weaned (NLB, NLW and KGW, respectively) in the first parity and first three parities (TNLB, TNLW and TKGW). These traits were studied in three combinations as follows:
1. WW, NLB and NLW.
2. WW, NLB and KGW.
3. YW, NLB and NLW.
The same combinations were used for the first three parities to estimate the heritability and variance components of these traits and to construct sex selection indices.
The statistical analysis of data was done on three main stages The first main stage was done with GLM procedure of the SAS program Institute Inc. (2000) in three steps. First step was to adjust KGW for the different fixed effects. Second step to correct WW at 60 days, YW at 365 days. Third step was to estimate least square means for all studied traits. The second main stage was to estimate variance components by using G-sample program. The third and last stage was to investigate and construct selection indices
The heritabilites were estimated for WW, YW, NLB, TNLB and TNLW were ranged from 0.03 to 0.09, 0.05 to 0.08, 0.04 to 0.07, 0.01 to 0.05 and 0.01 to 0.03, respectively.
And were 0.004, 0.06 and 0.01 for NLW, KGW and TKGW, respectively.
The positive genetic correlation was between WW with NLB, NLB with NLW, TNLB with TKGW and YW with TNLB.
The best selection indices were the first and fourth which were constructed from WW, NLB and NLW in the first parity and first three parities, respectively.
This investigation was carried out to estimate variance component (heritability and genetic correlation mainly), to investigate and construct sex selection indices to choose the more efficient index to use for evaluation and ranking ewes.
Data used in the present study were collected from Mallawy (south Egypt) experimental station belonging to the Ministry of Agriculture during the period from 1994 to 2010. The total available number of Farafra ewes and lambs in the present study was 837 and 1158, respectively. Mallawy station followed the system of three lambing per two years in the entire period.
The traits were used in this study were weaning and yearling weight (WW and YW, respectively) as a growth traits; and number of lamb born and weaned and kilograms weaned (NLB, NLW and KGW, respectively) in the first parity and first three parities (TNLB, TNLW and TKGW). These traits were studied in three combinations as follows:
1. WW, NLB and NLW.
2. WW, NLB and KGW.
3. YW, NLB and NLW.
The same combinations were used for the first three parities to estimate the heritability and variance components of these traits and to construct sex selection indices.
The statistical analysis of data was done on three main stages The first main stage was done with GLM procedure of the SAS program Institute Inc. (2000) in three steps. First step was to adjust KGW for the different fixed effects. Second step to correct WW at 60 days, YW at 365 days. Third step was to estimate least square means for all studied traits. The second main stage was to estimate variance components by using G-sample program. The third and last stage was to investigate and construct selection indices
The heritabilites were estimated for WW, YW, NLB, TNLB and TNLW were ranged from 0.03 to 0.09, 0.05 to 0.08, 0.04 to 0.07, 0.01 to 0.05 and 0.01 to 0.03, respectively.
And were 0.004, 0.06 and 0.01 for NLW, KGW and TKGW, respectively.
The positive genetic correlation was between WW with NLB, NLB with NLW, TNLB with TKGW and YW with TNLB.
The best selection indices were the first and fourth which were constructed from WW, NLB and NLW in the first parity and first three parities, respectively.