In crossbreeding program for five years involving the Saudi Gabali rabbits (S) and Spanish maternal line called V-line (V), two lines named Saudi 2 and Saudi 3 were synthesized to be convenient for hot climate. A total of 3496 litters of 922 does fathered by 199 sires and mothered by 451 dams were evaluated for milk yield at days intervals of 0-7, 7-21, 21-28, and total 0-28 and milk conversion ratio as kg of litter gain per kg of milk suckled. Across the six generations studied, Saudi 2 and Saudi synthesized are characterized by heterotic effects in milk yield and conversion since superiority rates for does of the two synthetic lines developed were 32.6, 29.4, 41.0, 29.6 and 35.0 % in MY7, MY21, MY28, TMY and MCR comparable to purebreds does, respectively. Estimates of direct, maternal, and grand-maternal heterosis for milk traits were moderate and significant, while the estimates of direct recombination effects were mostly non-significant. The cyto-plasmatic effects on milk traits were approvable to Saudi rabbits.