A three-year crossbreeding program between Aradi Saudi breed (A) with Syrian Damascus breed (D) was carried out in two experiments (one in Jouf and the second in Qassim,
Saudi Arabia) to produce four genetic groups of AA, DD, 1/2D1/2A and 3/4D1/4A in each experiment separately. A total number of 677 kids fathered by 36 sires and mothered by 335 dams were used to evaluate performance of kids in terms of growth, carcass and meat composition traits. A generalized least squares procedure was used to estimate direct additive genetic effects and direct and maternal heterosis. All estimates of direct additive effects
for growth traits in Jouf experiment were significantly high and in favour of Damascus kids by 12.0–31.9% for body weights and 13.7–30.6% for daily weight gains compared to the founder breeds (p < 0.01), while in Qassim experiment the estimates ranged from 17.1 to 34.2% for body weights and from 12.3 to 37.2% for daily weight gains (p < 0.01). Estimates of direct genetic effects for carcass traits were mostly significantly in favour of Damascus
goats, but these estimates were in favour of Aradi goats for meat compositions. Moderate and significant direct genetic effects for some carcass traits were in favour of Damascus goats by percentages ranging from 11.7 to 48.6% (p < 0.05 or p < 0.01) relative to the average
of founder breeds. Lean of Aradi kids had higher direct additive effects by 15.7% for dry matter content (p < 0.01) and by 2.8% for ether extract than lean of Damascus kids. Crossbred kids were associated with significant direct heterosis in the majority of growth
traits since heterotic increments were 0.16, 0.76, 0.93, 1.20, 0.79, 0.55 and 1.39 kg in Jouf experiment (p < 0.05) at 0, 4, 8, 12, 16, 20 and 24 weeks of age, while the respective increments in Qassim experiment were 0.31, 0.52, 1.39, 1.49, 1.43, 1.80 and 1.56 kg (p < 0.05
or p < 0.01). Pre-slaughter weight, hot carcass weight, and weights of head, skin, heart, and kidneys showed favourable positive estimates of direct heterosis of 1.35, 0.8 kg, 125, 93, 62, and 16 g, respectively. Estimates of maternal heterosis for growth traits in Jouf experiment
are mostly positively significant since these estimates were ranging from 2.4 to 10.7% for body weights and 2.4–8.4% for daily weight gains, i.e. crossbred dams of kids had moderate heterotic maternity over their purebred dams in most growth traits studied.
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