Seasonal infertility in sows: a five year field study to analyze the relative roles of heat stress and photoperiod.

The objective of this study was to analyze the relative roles of high temperature and photoperiod as environmental factors of seasonal infertility in swine. The results of five years (2003-2007) of ultrasound pregnancy diagnosis carried out in 266 indoor farms were analyzed. For all farms, the data covered the entire study period.