Heterosis for litter size traits in native by two exotic inbred pig crosses

Inbred strains generated from native and exotic pigs were compared with their F1and f2 backcross populations for a range of litter size performance traits. Animals were intensively reared and at 81⁄2 months of age, the inbred genotypes from each strain were reciprocally mated to each other to generate F1 crossbred genotypes; while gilts from each crossbred group were backcrossed to their male parents to obtain four backcross progeny groups. Litter size traits performances were better in the crossbred groups than in the inbred parents and this improvement could be ascribed to the dominant genes from the exotic parents. Significant (P<0.05) heterosis were obtained by the crossbred groups in most of the litter size characteristics like prolificacy, nursing ability, sex – ratio, litter weight and gestation lengths. The heterosis observed in the litter size traits were low and mostly non – significant. The backcross groups recorded residual heterosis in the litter size traits monitored and the magnitude was higher in the exotic than the native backcrosses. The results future indicate that the litter size traits performance of the crossbred groups were mostly influenced by maternal, sex –linked, dominance and epistatic gene actions. It could be suggested that the litter size traits production potential of the native pig could be improved further by cross mating selected native and exotic backcross pig. This could be followed by crises – crossing before group trait selection.