Estimation of additive and non-additive effects on milk production traits in Iranian Holstein crossbred population
Direct and interactive effect (individual and maternal heterosis) was estimated using data from rotational crosses between Holsteins with Iranian native breeds. Traits of interest were milk yield, fat yield, fat percent and milk days. Complete data were available on 155240 animals from 1991 through 2003. Direct additive’s effect, individual heterosis, maternal heterosis and recombination (interactions between presences of Holstein gene in two parents) effects were estimated by multiple regression method in SAS 8.2 with mixed models procedure. The least squares means of milk yield, fat yield, fat percent and milk days were 2722.68±1 541.12 kg, 122.97±47.40 kg, 3.97±0.73 percent and 260.10±89.51 days respectively. All direct and indirect genetic effects are significant in milk and milk days traits ( P<0.05). Individual and maternal heterosis and recombination effect are not significant on fat yield and fat percent traits. The individual and recombination effect were negative effect on milk yield. The result suggested that the Holstein is a favourable breed for crossbreeding program in developing country as Iran.