Light during incubation and noise around hatching affect cognitive bias in laying hens

T.B. Rodenburg, N.J.T. Scholten, E.N. de Haas

Research output: Chapter in Book/Report/Conference proceedingAbstract


Incubation and hatching conditions can influence development of laying hens. In commercial conditions, chicks are incubated in the dark and hatch in a noisy environment. This may affect their behavioural and cognitive development in a negative way and may have lasting effects on their assessment of ambiguous stimuli in a cognitive bias test. The aim of this study was to investigate the effects of light during incubation and noise around hatching on cognitive bias in adult laying hens. To meet that aim, eggs were incubated and hatched according to four different treatments in a 2×2 cross design: during the first 16 days of incubation, they would either be incubated in the dark or in a 12L:12D light schedule. From 17 to 21 days of age, half of the eggs from each light treatment would either be incubated in a noisy environment (playback commercial incubator noise; 90 dB) or a quiet environment (60-70 dB). Birds were kept in groups of maximum 10 birds in floor pens separated per treatment from 0 to 35 weeks of age (seven groups per treatment). At 35 weeks of age, 32 hens (eight per treatment) were trained for a cognitive bias test, where they had to learn that one side of the test arena was rewarded (mixed grains and mealworms) and the other side was not (smell of feed only). The rewarded side was varied according to a balanced design. The experimenter was blind to birds’ treatments. When a bird had learned the task, she was tested with ambiguous cues, where the feeder would be placed in the centre (50%), nearer the unrewarded side (25%) or nearer the rewarded side (75%). This was done by subjecting each hen to 12 trials, where two rewarded (R) trials and one unrewarded (U) trial (order RRU or RUR, balanced design) were followed by one of the ambiguous trials. For all hens, the first ambiguous trial was the 50% trial, followed by the 25% trial and the 75% trial. Latency to approach the feeder was analysed using a mixed model with treatment, trial order and type of cue as fixed factors (including all interactions) and pen nested within treatment as random factor. Over all treatments, birds had a shorter latency to reach the feeder with the rewarded cue compared to all other cues, and with the 50% and 75% compared to the unrewarded and 25% cue as expected (F4,360=211.4; P<0.001). There was a significant interaction between treatment and type of cue (F12,360=2.11; P<0.05). Birds from the light and noise treatment were slower than birds from the other groups in the ambiguous 50% trial (F1,360=3.49; P<0.05), which is interpreted as a more pessimistic response to the ambiguous cue. The light treatment during incubation may have resulted in a faster embryo development. This may in turn have resulted in chicks that were more sensitive to the noise treatment that was applied around hatching. In conclusion, incubation and hatching conditions in laying hens can affect cognitive bias in laying hens. Creating more quiet incubators and could have positive effects on laying hen welfare.

Original languageEnglish
Title of host publicationProceedings of the 51st Congress of the International Society for Applied Ethology (ISAE), 7-10 August 2017, Aarhus, Denmark
Subtitle of host publicationUnderstanding animal behaviour
EditorsMargit Bak Jensen, Mette S. Herskin, Jens Malmkvist
Place of PublicationWageningen
PublisherWageningen Academic Publishers
ISBN (Electronic)9789086868582
ISBN (Print)9789086863112
Publication statusPublished - 2017
Event51st Congress of the International Society for Applied Ethology (ISAE): Understanding animal behavour - Aarhus, Denmark
Duration: 7 Aug 201710 Aug 2017


Conference51st Congress of the International Society for Applied Ethology (ISAE)

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