Relative preference for wooden nests affects nesting behaviour in broiler breeders

Optimising nest design for broiler breeders has benefits for both the animals and producer.The welfare of the hens will increase by providing preferred housing, while also reducing eggslaid outside the nests. These floor eggs cause economic losses by compromised automaticegg collection and reduced saleability and hatchability. Attractiveness of nests can involvefactors as seclusion, material and nest climate. In this study, four nest box designs are offeredin a relative preference test: a plastic control nest, a plastic nest with a partition to divide thenest in two areas, a plastic nest with a ventilator underneath to create air flow inside the nestand a wooden nest. Six groups of 100 hens and 9 roosters had access to these four nests in arandomised location during the ages of 20 to 34 weeks. Nest and floor eggs were collected fivedays a week. Camera images from inside the nests made during the ages 25-26 wk and 27-28wk were analysed on behaviour. This included general activity, nest inspections, nest visitsand social interactions. At 32 wk of age the wooden nests were closed, and the subsequentresponse of the hens was monitored in terms of number of eggs. We found a clear preferencefor the wooden nest in number of eggs (69.3±1.0%) compared to the control nest (15.1±0.8%),partition nest (10.2±0.5%) and the ventilator nest (5.4±0.4%; P<0.0001). This preference wasalso reflected in increased time spent sitting, together with fewer nest inspections and visitsper egg laid in the nest. The preference for the wooden nest led to crowding, which caused anincreased amount of piling, nest displacement, aggression and head shaking. After the woodennests were closed, the hens still had preference for nest design, although this was stronglyinfluenced by the location of the nest. We conclude that the broiler breeder hens in this studyhad a strong preference for the wooden nests and the fact that they were willing to accept thecrowded circumstances in these nests, shows the strength of this preference. When deniedaccess to their preferred nest, the hens chose a new nesting location based on nest designdepending on proximity to their original nesting location. This study shows how the materialused for nests is an important factor in suitability and should therefore be taken into accountwhen designing nests. In future experiments we will investigate gregariousness nesting furtherin addition to studying the influence of genetics and mobility on nesting behaviour.