The sow or gilt should be mated twice, 12 to 18 hours apart, and the second service date recorded, say Graeme Taylor and Greg Roese, livestock officers at The Pig Site (thepigsite.com).
They add that during the interval, she should be returned to a pen or stall on her own. If she has to be returned to a group of sows, this should only be done after she has gone off heat. Check the sow 18 to 23 days after
