商業ブロイラーにおける恐怖反応および福祉パラメータに対する自然光および人工光処理の影響評価

In recent years, there has been a movement driven by consumer demands towards adding windows in broiler houses to allow for natural light during rearing; however, little is currently known about the effects of natural light on bird welfare. The objective of this study was to compare the impact of raising broilers under natural light or artificial light on fear response and welfare parameters. Mixed-sex Ross 708 chicks (N = 704) were housed in 16 rooms (44 birds/room), with 8 rooms per light treatment and raised until 56d of age. Chicks were randomly assigned to one of two light treatments: artificial light provided via a 5000 K LED (AL), or natural light provided via window and supplemented with 5000k LED (NL). Three fear tests were performed, novel object test (at 14d and 35d), response to observer test (at 14d and 35d), and novel environment test (at 55d). Welfare indicators such as footpad dermatitis, hock burn, gait score, and latency to lie were assessed at 55d of age. Data from the novel object test and the response to observer test were analyzed using Proc Mixed, whereas data from the novel environment test and welfare indicators were analyzed using Proc GLIMMIX (SAS 9.4). Results showed that broilers raised under AL were more reluctant to approach Zone 2 (1-meter radius) of novel object than NL broilers (P = 0.03). Birds exposed to NL had a shorter mean latency to approach the novel object (69.9 seconds) compared to those under AL conditions (181.4 seconds; P < 0.01). No treatment effects were found on the response to observer test, novel environment test, or welfare parameters except for footpad dermatitis, as bird raised under NL showed lower scores than AL birds (P = 0.03). Overall, this study indicates that the provision of NL did not show significant improvement in the fear levels or the welfare measures of leg health on broiler chickens.