Relationships between environmental conditions and behaviour of laying hens in an aviary system

The study explored the relationships between environmental conditions and behaviour of laying hens of two genotypes (225 brown- and 225 white-feathered) kept in two pens of a multi-tier aviary system. During the month of January 2024, for 3 weeks (hens from 31 to 33 weeks of age), environmental conditions as for temperature, humidity, CO2, NH3, decibel, lux, and particulate matter (PM1, PM2.5, PM4, PM10), were recorded using a multi-sensor placed at the animal level across the various tiers of the aviary: litter level (10 cm above the ground), between first-second tier (180 cm), and third tier (270 cm). Hen behaviour was assessed through the analysis of daily video recordings for 3 days. Correlations between environmental data and the number of animals showing behaviours at different hours and for all available recordings were calculated using PROC CORR of SAS. As for behaviours at the litter level, pecking and scratching were correlated with relative humidity, NH3, and lux (r=+0.15; P<0.001), whereas dust bathing was correlated with air particulate (PM2.5, PM4, and PM10) and temperature (r=+0.26 and r=+0.21, respectively; P<0.001). On the first tier of the aviary, scratching and pecking were positively correlated with humidity, NH3, lux, PM10 (r=+0.30; P<0.001), whereas preening was significantly correlated with NH3, lux, decibel, and particulate matter (r=+0.23; P<0.001). Resting on perches was negatively correlated with NH₃ and decibel (r=−0.32; P<0.001). On the second tier, resting on perches was negatively correlated with decibel, CO2, lux, and particulate matter (r=−0.26; P=0.001), whereas scratching and pecking were negatively correlated with temperature (r=−0.21; P<0.001), and positively with CO₂ and decibel (r=+0.18; P<0.001). On the third tier, pecking and scratching were correlated with light, humidity, NH3, and PM10 (r=+0.30; P<0.001). Resting on perches was moderately and negatively correlated with decibel, CO2, temperature, and particulate matter (r=−0.55; P<0.001) while resting and pecking showed weak correlations with NH3, lux, decibel, PM1 (+0.14 +0.21). In conclusions, over a short period of time (3 weeks) and under the controlled indoor conditions of the farm, behaviours of hens were significantly correlated with environmental variables, although the degree of the correlations was weak or moderate. In perspective, data collected over longer periods and in different seasons should be considered for a comprehensive evaluation. Research supported by Agritech National Research Center and was funded by the European Union – NextGenerationEU (Piano Nazionale di Ripresa e Resilienza (PNRR) – Missione 4 Componente 2, Investimento 1.4 – D.D. 1032 17/06/2022, CN00000022).