Relationships among steroid hormone levels in newborn piglets, birth weight, placental weight, vitality of offspring and litter size.

Blood estrone sulfate (E(1) S), estrone (E(1) ), estradiol (E(2) ) and progesterone (P(4) ) in newborn piglets were measured to clarify the relationships among birth and placental weight, vitality of offspring and litter size. First, the association between vital status (normal, weak and stillborn) from 165 newborn piglets of 18 litters and steroid concentrations; second, steroid concentrations from 152 newborn normal piglets and litter size; and third, steroid content in fetal placenta from 50 newborn normal piglets of six litters and litter size, were investigated. In the normal group, the birth and placental weight were significantly higher than those in the other groups. Blood E(1) S levels in the stillborn group were significantly lower, whereas E(1) , E(2) and P(4) were significantly higher compared to the normal group. Blood and placental E(1) S levels in the small litter group were significantly higher than those in the other groups. However, there was no significant difference among the three litter size groups in the levels of steroid hormones in maternal blood. These results indicate that vitality of newborn piglets is related to E(1) S concentration of neonate, to birth weight and placental weight. However, steroid hormone concentrations of newborn piglets were greatly affected by the number of littermates.