Selection index to improve growth traits and carcass composition in Lori-Bakhtiari sheep

Selection indices to improve growth traits and carcass composition for Lori-Bakhtiari sheep calculated. The selection goal comprised carcass lean weight (CMW) and carcass fat weight (TFTW) at six months of age and selection criteria were included live weight (BW6M)، estimated fat-tail weight (EFTW) and ultrasonic soft tissue depth (UGR) at six months of age. The expected annul responses to selection on different indices were culculated with relative economic values of 4. 61 and -0. 92 for carcass lean weight and carcass fat weight، respectively. The expected annul responses to selection on base different indices with different proportional ram (2، 4، 6، 8 and 10 percent) were calculated. Average ratios of selection intensity to generation interval، for the two sexes، were 0. 52، 0. 48، 0. 45 0. 43 and 0. 41، respectively. The highest expected response to selection annually were observed for increase lean weight and decrease fat weight with full selection index comprised BW6M، EFTW and UGR traits. The expected annul responses to selection ranged from 320 to 252 g CMW and from -118 to -93 g TFTW with selection index comprised BW6M، EFTW، and UGR traits for proportional ram 0. 02 to 0. 10. Economic response of full selection index and selection index included BW6M and EFTW traits were similar and higher than other indices. The efficiency expected response than direct selection for CMW and TFTW was 0. 82 with full selection index. The genetic gain annually of CMW decreased with increasing proportional ram and in difference selection goal and index. The lean weight than to fat weight decreased higher annually in full selection index.