Detection of estrus was performed twice daily using a sexually mature boar. Sows with
positive back-pressure test were taken to the breeding pens where they were artificially
inseminated. The first insemination was performed 12 h after estrus onset. The subsequent
inseminations were performed in 12–24 h intervals until estrus ended. Sows that presented
a weaning-estrus interval shorter than 1 day and the nulliparous females received the first
insemination at the onset of estrus.