Reproductive performance in relation to uterine and embryonic traits during early gestation in Meishan, Large White and crossbred sows

Previous studies have shown that females of the Chinese Meishan breed and of their F 1 , cross with European Large White pigs are very prolific, producing about four more piglets per litter than control Large White females. The main cause of this prolificacy is enhanced prenatal survival for a given ovulation rate in Meishan and F 1 females and this is controlled by genes of the mother, not those of the conceptus. The objectives of this study were to determine whether genotypic differences in embryo survival were apparent in the period immediately after attachment and to compare embryonic and uterine development at this time. Sows in their third parity (20 Large White, 14 Meishan, 25 Large White×Meishan F 1 and 25 Meishan×Large White F 1 ) were killed 20-22 days after mating and their reproductive tracts recovered for further study