The type of group housing for sows should be selected based on the overall target of the herd. Three options exist for feed control: average feed intake for all sows, equal intake for all individuals, and different amounts to different animals. Floor feeding, the most basic form of group housing, has issues with aggression and can only really see an appropriate average intake. These problems can be reduced (but not eliminated) by increasing space allowance and putting skinny sows into separate groups. A trickle system can provide a relatively even distribution of feed. Sows enter small individual stalls while feed is trickled down at an appropriate rate. Individual confinement is the only way to control individual feed intake. This is possible with stalls that lock the sow in and electronically controlled gates to allow different groups access to the feeding stalls at different times of the day. Electronic sow feeders are an alternative that electronically monitors how much a sow eats in a feeding area. This amount is reset daily, which allows for a daily allotment of feed for each sow. Social management of sows considers frequency of regrouping, sorting, and group size. A static group of sows are grouped once and only once during gestation while a dynamic group adds new animals on several occasions. Dynamic grouping could be detrimental to the sows welfare and productivity. One of the main benefits of group housing is the ability of the sow to manage its own comfort. Fairly rapid estrus detection can be achieved by bringing a boar to a pen adjacent to the group for a short period each day. If several animals need breeding they can be penned in stalls for a short time. Research done at the Prairie Swine Centre show that there was only a 2% difference in productivity between a static group, dynamic group, and conventional gestation stalls.