Effect of genotype, sex and parity on growth traits of diallel crossed Nigerian indigenous and exotic pigs
Three breeds of pig namely; Indigenous (IN), Large white (LW) and Landrace (LR) breeds were crossed in full diallel arrangement to evaluate the effects of cross, sex and parity on growth traits as well as establish the nature of gene action due to the growth traits at birth, weaning and 20 weeks of age. Each line crossed in a full 3x3 diallel cross resulted in a total of 132, 107 and 105 pigs at birth, weaning and 20 weeks of age respectively. General Combining Ability (GCA), Specific Combining Ability (SCA) and Reciprocal Effects (RE) were estimated for eight traits which includes Body weight (BWT), Ear length (EL), Tail length (TL), Heart girth (HG), Snout circumference (SC), Snout length (SL), Height at wither (HW) and Body length (BL). There were significant differences (P < 0.05) among the various crosses, sex and parity but no significant interaction. The LRxLW cross consistently expressed higher body weight and morphometric traits than other crosses at birth, weaning and 20 weeks of age, while the INxIN expressed least body weight at birth and 20 weeks of age, while LWxIN was the least at weaning. There was no significant GCA effect (P>0.05) on all the traits measured, but SCA was significant (P<0.01) for all morphometric traits and body weight. RE was significant for body weight at birth and weaning, while at 20 weeks, was significant for SC and HW. The non-significant GCA estimates along with significant SCA estimates suggest that the genes governing the eight traits measured do not act additively, but non-additively, implying that improvement of those traits may be attained by exploiting heterosis through planned crossbreeding. However, the significant reciprocal effect in body weight and some morphometric traits indicates maternal and sex-linked effect at the affected ages, implying that significant reciprocal cross may be used to attain high performance for the growth traits in the progeny.
Key words: Diallel cross, General combining ability, Specific combining ability, Reciprocal
effects, Indigenous pigs, Growth traits.