# Role of Illumination and Light Colour Temperature in the Preference Behaviour of Weaned Piglets

## TL;DR

This study shows that weaned piglets change their lighting preferences as they age, with implications for improving their welfare and housing design.

## Contribution

The study reveals how light intensity and color temperature affect piglet behavior and hygiene over time.

## Key findings

- Piglets initially preferred dark areas but later showed a shift towards illuminated areas with 3000 Kelvin color temperature.
- Piglets' lighting preferences changed with age and time of day, with no clear preference by the end of the study.
- Pens with 6500 Kelvin light were more soiled, suggesting a link between lighting and hygiene.

## Abstract

Light plays an important role in the behaviour, health and productivity of livestock. While the effects of day length on pigs—particularly in the context of reproduction—have been studied, little is known about how light intensity and colour temperature influence their behaviour. In this study, the impact of different brightness levels (80 lux and ~0 lux) and two-colour temperatures (bluish light at 6500 Kelvin and reddish light at 3000 Kelvin) was examined. The piglets were free to move between the different lighting conditions and were continuously observed by cameras, with their behaviour analysed afterwards. Initially, piglets in the first batch preferred darkened areas, whereas, in batch two, they stayed in the illuminated pens, especially when the colour temperature was 3000 Kelvin. However, this changed as the animals grew older, with the piglets’ preference shifting towards the darker areas until, by the end of the study, no clear preference could be detected. While the darkened areas remained largely clean, the area with the 6500 Kelvin colour temperature was more frequently soiled with faeces. These findings suggest that pigs respond to different lighting conditions and may benefit from lighting concepts aligned with their natural behaviour. This knowledge can help improve both animal welfare and the design of pig housing in swine production.

This study investigated the preference behaviour of 24 four-week-old weaned piglets under different lighting conditions (0 lux with 0 Kelvin vs. 80 lux with 3000 Kelvin vs. 6500 Kelvin). Two trials with 12 piglets each were conducted over five weeks in a room with four interconnected pens, allowing free movement between the pens. Pens A and B were nearly dark (~0 lux), while pen C (80 lux, 3000 Kelvin) and pen D (80 lux, 6500 Kelvin) were illuminated. On three days in weeks 1, 3 and 5, behaviour (lying, eating and activity) was recorded using video observations and a 5 min time sampling method. Cleanliness was also monitored daily. In the first week, piglets in the first batch preferred the darkened pens, whereas piglets in the second batch preferred illuminated pens, especially when the colour temperature was 3000 Kelvin. By the third week, piglets in the second batch now preferred darker areas. In the fifth week, the piglets spent more time in the dark in the mornings and evenings but showed no preference for colour temperature. The darkened pens remained mostly clean, whereas pen D, which had a light colour temperature of 6500 Kelvin, was the most soiled. The results show that piglet behaviour changes with age and the time of day, suggesting that lighting concepts can be adapted to improve both animal welfare and pen hygiene.