Abstract:
The reproductive performance of pigs is one of the main determinants of the profit farmers
make from pig production. This study was undertaken to describe whether periods of high
environmental temperature have an effect on the farrowing rate, litter sizes and number of
stillbirths in commercial breeding units in South Africa. Data were collected weekly from four
commercial breeding units with good records from December 2010 to August 2012. These
data included the number of sows mated, number of sows farrowed and number of piglets
born alive, as well as the number of stillbirths. Note was also taken of whether environmental
temperature control mechanisms were employed. Temperature data from weather stations
within 100 km of the breeding units were obtained from the South African Weather Service.
In all breeding units a decrease in farrowing rate following mating during severe average
temperatures (> 30 °C) when compared to the farrowing rate following mating during mild
average temperatures (< 22 °C) was observed. When mating occurred at higher temperatures,
the resultant litter size was marginally decreased in the breeding units that did not employ
environmental temperature control, but was unaffected in the breeding units that did. In all
four breeding units the trend was for the average number of piglets born alive to increase
as the environmental temperature around the time of farrowing increased and the trend in
three of the four breeding units was for the percentage of stillbirths per litter to decrease with
increased temperature around the time of farrowing. The most significant observation in this
study was the trend for farrowing rates to decrease following inseminations during times of
high ambient temperatures (> 30 °C). Environmental temperature control did not negate this
effect, but the breeding units employing the environmental temperature control did show
higher average farrowing rates overall.
