Yang Yang, Cong Wei, Liu Jie, Zhao Mindie, Xu Peirong, Han Wanwan, Wang Deyun, Zhao Ruqian
MOE Joint International Research Laboratory of Animal Health & Food Safety, Institute of Immunology, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
J Anim Sci Biotechnol. 2022 Jun 21;13(1):67. doi: 10.1186/s40104-022-00720-4.
Light management plays an important role in the growth and behavior of broiler chickens. Constant light in early post hatch stage has been a common practice in broiler industry for improving growth performance, while whether and how constant light in early life affects the behavior of broiler chickens is rarely reported.
In this study, newly hatched chicks were kept in either constant (24 L:0 D, LL) or (12 L:12 D, LD) photoperiod for 7 d and then maintained in 12 L:12 D thereafter until 21 days of age. Constant light increased the average daily feed intake but not the body weight, which led to higher feed conversion ratio. Chickens in LL group exhibited fear-related behaviors, which was associated with higher corticosterone, lower melatonin and 5-HT levels. Concurrently, constant light exposure increased the mRNA expression of clock-related genes and suppressed the expression of antioxidative genes in the hippocampus. Moreover, brain derived neurotrophic factor/extracellular signal-regulated kinase (BDNF/ERK) pathway was suppressed in the hippocampus of chickens exposed to constant light in the first week post hatching.
These findings indicate that constant light exposure in early life suppress melatonin secretion and disrupts hippocampal expression of genes involved in circadian clock and BDNF/ERK pathway, thereby contributing to fear-related behaviors in the chicken.
光照管理在肉鸡的生长和行为中起着重要作用。孵化后早期阶段持续光照是肉鸡行业提高生长性能的常见做法,然而早期持续光照是否以及如何影响肉鸡行为的报道却很少。
在本研究中,刚孵出的雏鸡在持续(24小时光照:0小时黑暗,LL)或(12小时光照:12小时黑暗,LD)光周期下饲养7天,之后维持在12小时光照:12小时黑暗直至21日龄。持续光照增加了平均日采食量,但未增加体重,这导致了更高的饲料转化率。LL组的鸡表现出与恐惧相关的行为,这与较高的皮质酮、较低的褪黑素和5-羟色胺水平有关。同时,持续光照增加了时钟相关基因的mRNA表达,并抑制了海马体中抗氧化基因的表达。此外,在孵化后第一周暴露于持续光照的鸡的海马体中,脑源性神经营养因子/细胞外信号调节激酶(BDNF/ERK)通路受到抑制。
这些发现表明,早期持续光照会抑制褪黑素分泌,破坏海马体中参与昼夜节律时钟和BDNF/ERK通路的基因表达,从而导致鸡出现与恐惧相关的行为。