Statistical analysis was conducted on sow stillbirth traits of three mating types with 1686 litters including Erhualian, Large White and F1. The number of stillborn piglets per litter (NSB) in Erhualian, Large White and F1 averaged 0.87, 0.32, 0.72, and the percentage born alive (PBA) averaged 95.1%, 97.1% , 95.7% , respectively. The Erhualian pig with a higher litter size also had a higher stillbirth rate. The results of the variance analysis indicated that the mating type, parity, farrowing year X farrowing season interaction and the total number born had highly significant effects on both NSB and PBA in sows (P < 0.001). Farrowing season had highly significant effects on NSB (P<0.01), and significant effects on PBA (P< 0.05). Farrowing year had no significant effects on NSB (P >0.05), and highly significant effects on PBA (P < 0.01). From parity 1 to parity 10, the least square means for NSB progressively increased with increasing parity, the least square means for PBA progressively decreased with increasing parity. The sows farrowed in winter had the highest NSB and the lowest PBA, the sows farrowed in autumn had the lowest NSB and the highest PBA. The least square means for NSB markedly increased with an increase in the total number born, indicating that the positive phenotypic correlation existed between them. The least square means for PBA markedly decreased with an increase in the total number born, indicating that the negative phenotypic correlation existed between them. The estimating results of the paternal half sib indicated that the heritabilities for NSB and PBA were 0.111 and 0.123, the genetic correlation, phenotypic correlation and environmental correlation between them were -0.985, -0.947 and -0.942, respectively.
CHU Ming-xing,WANG Ping-qing and WU Chang-xin( Institute of Animal Science , Chinese Academy of Agricultural Sciences , Beijing 100094 , P. R. China
