EFFECT OF TYPE OF CROSS ON LITTER SIZE AND LITTER WEIGHT OF PUREBRED AND CROSSBRED SWINE

Data on 321 litters from the first three gestations of purebred and si ngle crosses of Duroc (D), Landrace (L), Yorkshire (Y) and Large White (LW) swine were analyzed by least squares to evaluate the effects of breed, general combining ability, specific combining ability, maternal and reciprocal effects and total and specific heterosis on total numb er of piglets at birth (TNPB), number of piglets alive at birth (NPAB) , at 21 days (NP21), at weaning (NP35) and at the end of the growth pe riod (NP77) as well as litter weight at birth (LWB), at 21 days (LW21) , at weaning (LW35) and at the end of the growth period (LW77). Purebr ed Large White litters had a better performance than Duroc litters for traits: NPAB, NP21 and NP35. Breed significantly affected LW35, thoug h there were no differences among L, LW and Y breeds, which had heavie r litters compared to Duroc. There was no significant effect of genera l combining ability either on litter size or litter weight. Specific c ombining ability significantly affected only LWB. Better performance w as observed for D x Y and L x LW crosses. Maternal effect had no signi ficant effect on litter size traits, but significantly affected LWB, L W21 and LW35. Lower litter weights were observed for LW breed (LWB) an d D breed (LW21 and LW35). Reciprocal effect and total heterosis did n ot affect any of the traits. Significant effects of specific heterosis (P less than or equal to 0.05) were observed only for D x Y crosses, with estimated values of 21.84% (LW35) and 22.50% (LW77).