Liu, Z., Torrey, S., Newberry, R. C. et al. 2020. Play behaviour reduced by environmental enrichment in fast-growing broiler chickens. Applied Animal Behaviour Science 232, 105098.

The objective of this study was to evaluate effects of environmental enrichment on play behaviour in fast-growing broiler chickens. Chicks (19 of each sex) were randomly assigned to 6 non-enriched (NE) pens and 6 pens enriched (E) with a raised platform, hanging weighing scale, peck stone, and suet feeder filled with wood shavings which was refilled every other day. Three worm running tests (on days 10, 24, and 38), and three free-space tests (on days 8, 21, and 35) were performed to stimulate play behaviour. From video recordings, occurrences of worm exchange, worm pecking, worm chasing, and worm running in the worm running tests, and running, frolicking (i.e. running with wing use), wing flapping (while stationary), and sparring in the free-space tests, were quantified. Video recordings were also made on days 23, 30, and 37 to observe spontaneous play. Generalized linear mixed models were used to investigate effects of enrichment, age and their interaction on occurrence of the different forms of play behaviour per bird per 5 min in the worm running and free-space tests, and per hour in spontaneous play observations. In worm running tests, chickens in NE pens performed more worm exchange (P = 0.034), worm chasing (P < 0.001), and worm running (P = 0.035) than those in E pens. In free-space tests, running (P < 0.001), frolicking (P = 0.016), and all play behaviour combined (sum of running, frolicking, wing flapping, and sparring; P < 0.001), were more frequent in NE than E pens. In the test contexts, worm chasing declined with age in both NE and E pens (P < 0.001), and running, frolicking and all play behaviour combined declined with age in NE pens while remaining low and unchanged in E pens. In contrast, occurrence of worm pecking (P = 0.004) and wing flapping (P < 0.001), both performed while stationary, increased with age in both NE and E pens. Total spontaneous play behaviour (sum of running, frolicking, wing flapping, and sparring) did not differ between treatments (P = 0.644) but did decline with age (P = 0.013). In conclusion, while NE birds did not differ from E birds in the performance of spontaneous play, they were more responsive than E birds during tests intended to stimulate play behaviour in broilers. This was possibly because of the larger contrast between their relatively unstimulating environment and the test conditions, resulting in them being more easily aroused. The findings also show that the worm running and free-space tests were effective in stimulating play.