Management factors affecting activity and aggression in dynamic group housing systems with electronic sow feeding: a field trial

A series of 24-h video studies an four commercial Danish pig herds investig ated the behaviour of pregnant sows kept in dynamic groups (72 to 200 sows) with electronic sow feeding (ESF). The herds mainly differed with respect to provision of a layer of unchopped straw as bedding material, the frequen cy of introduction/removal of animals, space allowance in the lying area, g roup size and number of feeding stations, and starting times for the feedin g cycle. All herds had one feeding cycle per 24 h. Six 24-h video recording s in the most settled period with respect to rank relationships (2 to 12 da ys after the last introduction) were collected from each herd and analysed according to activity and aggressive interactions. In two of the four herds recordings were collected in two separate periods with different starting times for the feeding cycle. In all herds peaks of activity in the morning and in the afternoon were evident. Furthermore, the diurnal variation was o verlaid by an increase in activity at the start of the feeding cycle. The a ctivity and aggression in the feeding area as well as the duration per sow of the period with high feeder occupation were lowest in herds where a laye r of straw bedding was provided. Changing feeding start from day time to ni ght time was accompanied by a reduced feeder occupation in the period follo wing start of the feeding cycle. However, in herd 1 (characterized by no li tter, high stocking density and high frequency of grouping) the level of ag gression was reduced, whereas it was increased in herd 2 (characterized by straw in lying area, low stocking density, low frequency of regrouping). Nu mber of regroupings and space allowance apparently had no obvious effects o n the average frequency of aggression or the aggression per sow at risk in periods between introduction of new animals, but space allowance may have i mproved social function by weakening the association between activity and a ggression. Due to the small number of herds included the present results we re descriptive rather than conclusive. However, the study supports the sugg estions that provision of unchopped straw as bedding material and starting the feeding cycle in the evening for overnight feeding may improve behaviou r in dynamic group housing systems with ESF However, the benefits of starti ng the feeding cycle in the evening may depend on low disturbance in daytim e from other management procedures.