Learning, health and productivity of group-housed sows conditioned to signal-feeding under realistic husbandry conditions

Signal-feeding is a discrimination task for pigs where individual acoustic signals indicate the availability of feed at an electronic feeding station. It has been shown that this feeding technique has the potential to reduce agonistic interactions between pigs and improve animal welfare. As a side effect, signal-feeding was found to facilitate the accessibility of the feeding stations. Therefore, this feeding system may have the potential to improve the pigs' overall feed supply and productivity. Signal-feeding has been successfully adapted for use with adult sows at conventional electronic feeding stations and was tested under near-practical conditions. The present field study was conducted to test the applicability of signal-feeding under the realistic conditions of a conventional piglet rearing facility. The aim was to verify that sows can cope with the signal discrimination task under the limitations of intensive livestock farming which comprises large groups with high feed concurrence and only one training opportunity per day. Furthermore, the study should confirm any positive effects on the animals' health and welfare and, for the first time, substantiate the economic viability of signal-feeding by demonstrating a reduced workload and increased productivity compared to conventional electronic feeding stations. As a main result of the study, we observed that a single training opportunity per day and training in groups of more than 30 sows resulted in a training duration that ranged from 12 to 38 days for the majority of sows. The liquid feeding system utilised was found to be inadequate for reward delivery. It left feed remains on the station floor and could not provide the feed reward in sufficiently close temporal relation to the animal behaviour. The feed remains in combination with the somewhat random reward delivery created sufficient motivation for some sows to continue visiting the feeding station. As a result, no improvements in the accessibility of the feeder were observed. Under these conditions, we did not find any effects on the productivity of the sows in terms of the number of piglets born alive or the number of weak or crushed piglets. However, the training itself led to an increased number of shallow skin lesions and higher medical costs at the beginning of the study when the majority of sows received their conditioning. This effect disappeared later, when only replacement sows were trained. This study demonstrates that in sows an automated operant conditioning of a complex signal discrimination task is possible even under the considerable limitations of intensive livestock farming. However, future studies