Preference of Commercial Free-Range Layers for Shelters of Different Sunlight Filtering

Free-range commercial layer farming in Australia has been increasing for the last decade in response to consumer demand for free-range eggs. To meet this demand, there is a focus on research to optimise free-range system design and management. A range of external factors have been shown to impact hens’ daily outdoor range use including weather conditions, time of day, season and range enrichments (Richards et al., 2011; Larsen and Rault, 2021). Sunlight intensity and ultraviolet radiation could be factors affecting use of the outside range in free-range systems. Artificial shelters within the range could provide protection from sunlight for free-range hens in Australian climates with more extreme sunlight.

This study was conducted across two individual flocks (Flock-A, and Flock-B) of a commercial free-range layer farm (December 2020 to March, 2021) in Queensland, Australia to assess hen preferences for artificial shelters of commercially available shade cloths of different densities. Three types of shade cloth shelters with three replicates each were used including (i) 50% UV block, (ii) 70% UV block, and (iii) 90% UV block across two flocks consecutively. Although the shade cloths are marketed as blocking UV radiation, they also filtered out solar radiation in the visible spectrums and are hence referred to as ‘sunlight filtering’. Each shelter (4 m L x 3 m W x 1 m H) was positioned in a straight line parallel with the shed 10.5 m away from the pop holes. Both flocks consisted of approximately 20,000 Hy-Line Brown laying hens, and all observations were taken between 34 to 40 weeks of age. A high-resolution security camera system was installed for recording the hens’ preferences across daylight hours. A weather station was set-up at the respective farm site with different sensors to record the irradiance of sunlight spectrums including ultraviolet radiation (UVAB) (280-400 nm) (W/m²), photosynthetically active radiation (PAR) (400-700 nm) (μmol/m2 /s), and total solar radiation (TSR) (100 nm- 1 mm) (W/m²) [TSR was later used to extract infrared radiation (IR) (W/m²)] along with an ambient air temperature and relative humidity sensor. A total of 14 days of video for Flock-A and 17 days for Flock-B were analysed with image snapshots at 30-min intervals used to count the number of hens under the individual shelters. Data were analysed by JMP® 14.0 to test hens’ shelter preferences across the day using GLMMs. The relationship of sunlight and weather variables with hens’ shelter preferences was determined by fitting linear ridge regression models using ‘lmridge’ package in R statistical software.

There was a significant interaction between sunlight-filtering shelter and time of day for hen preferences in both Flock-A (F (36, 2331) = 3.49, p < 0.0001), and Flock B (F (36, 2844) = 2.63, p < 0.0001) where more hens preferred the 90%, followed by the 70% then 50% sunlight-filtering shelters. The overall use of shelters by hens significantly varied across the time of day with peaks in the morning and in the late afternoon compared to the mid-day (both flocks, P < 0.0001). Among the sunlight and weather variables, the majority of the variance in the models resulted from the ambient temperature in both study flocks; however, UVAB was also significantly correlated with hens’ shelter preferences in Flock-B. The study indicated that the higher level of sunlight-filtering shelters on the range were preferred by hens. However, there were still lower numbers of birds outside during the midday period suggesting hens prefer to remain indoors at this time despite the available range shelters.