Data from 1,909 purebred, F1, backcross and @entity9900 inter se combinations of Angus and Hereford were used to estimate average individual, maternal and grandmaternal genetic effects, individual and maternal heterosis, dominance and epistatic genetic effects. Models for evaluating heterosis and epistatic or recombination effects were discussed. Average individual effects indicate that Angus, compared with Hereford, had @entity291 that were born earlier, had lighter birth weights, lower pre- and postweaning gains and lower pregnancy rates. Angus also produced lighter weight carcasses with more fat cover and marbling. Maternal effects of Angus were in the direction of reduced birth weight, greater calving ease, higher preweaning but lower postweaning growth rate and increased @entity1386 when contrasted with Hereford. There was a tendency for opposite direction of maternal and grandmaternal effects for traits influenced by preweaning maternal environment. When additive X additive effects were ignored, total heterosis was significant for earlier day born, heavier birth weight, preweaning and postweaning gain, and heavier and fatter carcasses. Heterosis retained in F3 inter se vs F1 generation crosses indicated that net epistatic effects were relatively negligible for date of calving, birth weight, @entity1017 and fat cover. There was a greater reduction of heterosis effects than expected from dominance alone for survival, pregnancy and marbling score. Loss of heterosis in F3 was less than expected for postweaning gain, carcass @entity735 . Except for survival, pregnancy and marbling, these deviations from dominance expectations, or lack of them, are favorable for F3 composite populations.

Heterosis retained in advanced generations of crosses among Angus and Hereford XXXX .

@entity9900 :: ('280685(Tax:9913)', 'Gene') :: ['F2 and F3'] @entity735 :: ('MESH:D005124', 'Disease') :: ['weight and rib eye area'] @entity1017 :: ('MESH:D015430', 'Disease') :: ['weaning gain'] @entity291 :: ('9913', 'Species') :: ['calves'] @entity1386 :: ('MESH:D018205', 'Disease') :: ['fatness']
@entity291 :: (9913,Species) :: ['cattle']
