Delayed development in Large White purebreds than crossbreds with Meishan born in the same litter
Résumé
A crossbreeding design based on the use of mixed semen from Large White (LW) and Meishan (MS) boars was set up to study differences in late development of purebred and crossbred fetuses developed in the same uterine environment, i.e. either LW or MS. Caesareans were performed at the end of the second gestation to study characteristics of fetuses at 90 d and 110 d of development. A total of 312 fetuses from 9 LW and 10 MS sows were dissected. The four genetic types of piglets were compared according to body, bones and organs traits measured on the experimental farm or from image analyses. The model for statistical comparison included the fixed effect of sex, the interaction between genetic type and age of development, the percent of purebreds in the litter and litter size as covariates, and the sow random effect. Purebred (PB) and crossbred (CB) fetuses differed for body weight and body length at 90 d and 110 d of development in MS sows (P<0.05) but not in LW sows. LW PB were heavier and longer than MS PB at 110 d but not 90 d (P<0.05). The body mass and ponderal indexes of LW PB were lower than those of LW CB at 90 d and 110 d, and of MS PB and MS CB at 90 d only. These indexes were lower in MS CB than MS PB at 90 d but the difference disappeared at 110 d. Proportionally to body length, the femur was the shortest in LW PB, intermediate in the 2 reciprocal CB types, and the longest in MS PB (at 90 d). Proportionally to body weight, liver was the lightest in LW PB, of intermediate weight in the 2 CB types, and the heaviest in MS PB (P<0,05). Ratios of the brain weight above weight of several organs at 90 d were the highest in LW PB, intermediate in the 2 CB types, and the lowest in MS PB, indicative of sparing effects in LW PB. Our findings outlined a delay of late fetal development in LW PB fetuses. The complementary comparison of born alive LW PB that died or survived the first 24 h after birth confirmed that disproportionate development is correlated with lower survival.