In Sweden, the interest in use of electronic sow feeding (ESF) systems for group-housed gestating sows is growing. The use of ESF systems is associated with several benefits as the system allows for e.g. individual feeding of animals and saves space in the barn when sows are housed in large groups. Housing gestating sows in an ESF system is, however, also associated with several challenges. Gestating sows are fed restrictive amounts of concentrates to reduce reproductive problems, which means that the sows may likely still be motivated for eating/feed seeking. A lasting motivation for eating/feed seeking combined with group housing on relatively confined space, will result in increased levels of aggression, following increased competition. We expect that provision with roughage will increase satiety and thereby lower the level of aggression in the pen and improve the clinical condition of the sows.
Project was completed in 2020
The study supports the existing findings, that vulva biting is a welfare problem, when sows are housed in an ESF-unit. Aggression did occur and the level of aggression, as reflected by the level of skin lesions, appeared to decrease over time in the higher parity sows but not in the younger sows. Accordingly, both Arey (1999) and O’Connell et al., (2003) suggested that in particular the welfare of low ranking animals (which are most often the younger animals) may be challenged (e.g. have more injuries and be positioned lower in the feeding order) in high competition housing systems such as the ESF-system.
Contrary to the expected, provision with hay silage had no significant effects on any of the recorded variables. A reason for this may be the low amounts of silage provided. When providing sows with access to grass silage, O’Connell (2007) found that sows consumed an average of 1.8 kg daily, which is far from the <300 g/sow/day provided in the present study. Thus, the small amounts may not have been enough to affect the satiety level of the animals or occupy them to a level affecting the group dynamic in the pen. Furthermore, the sows only had access to two hay racks per ESF pen, which were located relatively close to each other and only two sow lengths from the entrance of the feeding station.
Future studies should consider using larger amounts of hay silage and consider providing better access to this resource to avoid the risk of simply creating another limited resource in the pen. In the present study the two hay racks were placed in an area with solid concrete, intended as a lying area. Even a solid lying area can be considered as a limited resource at the minimum dimensions that apply to ESF systems.
The results from the measurements of back fat showed a relatively large proportion of fat sows. The reason for this is unclear, but may be explained by the fact that the amount of feed delivered by the feed stations were not correctly calibrated. Constant calibration of the feed stations is important for an optimal operation.