Analysis of reasons for sow culling and seasonal effects on reproductive disorders in Southern China.

Sow culling rates have a direct correlation to the economic efficiency of both breeding herd and commercial herd. Analyzing the reasons of sow culling could lead to improve production efficiency of farms. This study, which involved inspections of four farms in Southern China, manifested that the rate of unplanned sow-culling has reached to 78.1% in total culls. In which, reproductive disorders and lameness accounted for 35.3% and 22.5%, respectively. The average parity of culled sows was 4.9, but a high proportion (19.6%) of sows was culled at their first parity. Anestrus, the highest proportion of reproductive disorders, accounting for 47.7%, occurred in July followed by June (17.7% and 11.8% respectively). The frequency of culling due to reproductive disorders in Southern China was higher than others regions, which suffered from the high temperature and humidity in Southern China. The frequency of sow culling reached its peak in the summer, specifically in July (12.3%), which means that hot weather has an adverse effect on sow culling. Pig farmers should take effective measures to reduce heat stress as nutrition strategies or cooling systems in gestation and/or farrowing sow herds between May and July in Southern China.