Partitioning of genetic effects on lifetime performance of mice

Summary A total of 2,457 lifetime performance records of 29 genetic groups of mice was analyzed using multiple regression of records on the proportion of gene contribution from 6 lines (designated as Lines M_P, m_Q, W_P, w_Q, C_P and c_Q). Genetic effects were partitioned into line additive, line maternal, direct heterosis, maternal heterosis and paternal heterosis effects. The line additive and line maternal effects were expressed as deviations from Line c_Q. Seventeen of 25 line additive effects differed significantly (P<0.05) from Line c_Q whereas only 4 of 25 line maternal effects deviated significantly from Line c_Q. Deviations in line additive effects from c_Q were negative in all lines examined whereas deviations in line maternal effects from c_Q were all positive, indicating a negative relationship between line additive and line maternal effects. Direct heterosis effects were all positive and significant (P < 0.01) except in the M_PxW_P cross which was produced by mating Lines M_P and W_P of the same base population (P). Maternal heterosis effects were significant in 10 of 20 cases whereas paternal heterosis effects were significant in 13 of 20 cases. Although direct heterosis is a major component of total heterosis effects (sum of direct, maternal and paternal heterosis), the results suggest that parental heterosis may need to be considered in producing multiple way crosses. The fitting of line additive, line maternal, direct heterosis, maternal heterosis and paternal heterosis effects in the multiple regression model effectively accounted for all genetic effects in lifetime performance.Animal Research Centre Contribution No. 1326