An evaluation for five-year crossbreeding project was performed for pre-slaughter weight (PSW), weights of hot carcass (HCW) and offal (OW) as edible carcass, dressing percentages (DP), weights of head (HW), fur (FURW), lung (LW) and viscera (VW) as non-edible carcass traits, weights of meat (MW), bone (BW) and fat (FW) as tissues composition and percentages of dry matter (DM), crude protein (CP), ether extract (EE) and ash in the lean as meat quality traits. This crossing project involving a Spanish maternal line called V-line (V) and a Saudi Gabali (S) rabbits and 14 genetic groups of V, S, ½V½S, ½S½V, ¾V¼S, ¾S¼V, (½V½S)2, (½S½V)2, (¾V¼S)2, (¾S¼V)2, ((¾V¼S)2)2, ((¾S¼V)2)2, Saudi 2 (synthesized maternal line), and Saudi 3 (synthesized paternal line) were produced in this project. A total number of 2770 rabbits fathered by 91 sires and mothered by 402 dams were slaughtered. Heritability and common litter effects were estimated using an animal model and solutions of the mixed model equations for the genetic group effects were estimated to identify the possibilities of using Saudi 2 and Saudi 3 as synthetic lines in hot climate areas.

Heritability estimates were mostly moderate and ranging from 0.17 to 0.22 for edible carcass traits, 0.12 to 0.22 for non-edible carcass traits, 0.14 to 0.20 for lean composition traits, and 0.12 to 0.36 for meat quality traits. For common litter effects, the estimates were mostly moderate or high and ranging from 0.31 to 0.35, 0.29 to 0.39, 0.15 to 0.29, and 0.17 to 0.23, respectively. Relative to line V or Saudi Gabali, Saudi 2 (with ¾ of its genes coming from line V) and Saudi 3 (with only ¼ of its genes coming from line V) were mostly significantly superior in PSW, edible carcass (HCW, OW), DP, non-edible carcass (HW, LW, VW), tissues composition (MW, BW), MBR, and meat quality traits (DM, EE and ash). In most cases, the estimates for Saudi 2 were found to be significant ranging from 5.3 to 17.0% for slaughter and edible carcass traits, from 9.7 to 18.1% for non-edible carcass traits, 7.5 to 15.1% for tissues compositions, and 3.8 to 39.2 % for meat quality traits comparable to purebred Saudi rabbits, while the estimates for Saudi 3 ranged from 8.6 to 18.6%, 11.7 to 18.8%, 8.5 to 13.9%, and 3.2 to 47.1%, respectively.

In practice, both Saudi 2 and Saudi 3 could be used as specialized synthetic lines convenient for hot climate countries since they were significantly superior in carcass performance, lean composition and meat quality traits relative to the founder lines.