Influence of access to maize silage on sham chewing and stomach ulcer of gestating sows

Diets of gestation sows are typically restricted to ~60% of their ad libitum intake. In addition, these diets are often offered daily with a concentrated feed, and as a result, the sows are likely to have an unfulfilled feeding motivation. Both hunger and lack of ability to perform foraging behaviours contribute to stereotypic behaviours, such as sham chewing (D’Eath et al. 2009). O’Connell (2007) and Stewart et al. (2010) found that the combination of a high fibre diet with access to straw reduced sham chewing compared to a control diet without straw. Giving finishers permanent access to wrap hay from racks, in addition to standard Danish pelleted diet, (Poulsen and Thoning 2015) could reduce the incidence of gastric ulcer. The aim of this study was to assess the effect of providing supplementary maize silage on stomach ulcers in culled sows and sham chewing of gestating sows in groups. It was hypothesised that maize silage would reduce stomach ulcers and sham chewing.

A total of 2988 gestation sows in two different Danish herds with group housing were included in the study. Both herds had ~1200 sows and the sows were inserted into the gestation pens 4 weeks after weaning. In each herd, the sows were either given 3 kg of maize silage on the floor at feeding once daily, or no roughage (control). All sows were offered straw as bedding (legislation). Data was collected on farm by a technician from the Pig Research Centre. Sows chewing with white foam and no feed/straw in the mouth were defined as sham chewing. In both herds, the sows were examined 5 h after feeding. After weaning, stomachs from culled sows were examined for stomach ulcers and given a score from 1 to 10 according to severity (Jensen et al. 2017).

Stomach ulcers were analysed by a Chi-test and data on the percentage of sows per pen sham chewing were analysed by a t-test (SAS v7.1, SAS Institute Inc., Cary, NC, USA). Each herd was analysed separately and the results are shown in Table 1.

Maize silage given as a supplement during the gestation period had no effect on stomach ulcer in culled sows at weaning. Maize silage reduced the proportion of sows sham chewing significantly in both herds compared with sows only offered straw as bedding. In conclusion, 3 kg of maize silage per sow per day in the gestation period had a positive influence on the percentage of sows sham chewing, but no influence on stomach ulcer at weaning.

Table 1.  Effect of maize silage on stomach ulcers at weaning and sham chewing five hours after feeding