Effects of a dynamic light schedule on sustainability indicators in finishing pig production

We investigated if mimicking natural daylight improves social, environmental and economic sustainability in pig production. A dynamic light treatment was compared to a reference treatment consisting of TL (tube lights) using 224 pigs. Dynamic light included gradual changes in intensity at the start and end of the day, variation in color temperatures and a higher average intensity. Gradual intensity changes were hypothesized to improve synchronous (in)activity and thereby stimulate functional pen use. Variation in color temperatures in combination with a higher intensity were expected to benefit pig welfare. Hypotheses were partly confirmed, with a tendency for better space use under dynamic light (more pigs lying in the resting area), but more pen fouling in the feeding area. Effects on animal welfare were also contradictory. Dynamic light increased damaging manipulation, tended to worsen ear lesions, and increased non-resource-related aggression. Contrastingly, dynamic light reduced resource-related aggression, dog-sitting, and conjunctivitis scores, and tended to reduce total aggression frequency. Feed use was higher under dynamic light, while weight gain did not differ between treatments. Electricity use and net income change were less favorable under dynamic light, partly due to the increased number of light sources required to generate higher intensity. The stockkeeper slightly preferred working with the dynamic light. Light did not affect play behavior, production performance, post-mortem abnormalities, tear staining, bursitis and aggression-related skin lesions. To conclude, dynamic light did not clearly outperform TL, as both positive and negative effects were observed. Further research is recommended to optimize light schedules in pig housing.