Constant light in early life induces fear-related behavior in chickens with suppressed melatonin secretion and disrupted hippocampal expression of clock- and BDNF-associated genes

Yang Yang; Wei Cong; Jie Liu; Mindie Zhao; Peirong Xu; Wanwan Han; Deyun Wang; Ruqian Zhao

doi:10.1186/s40104-022-00720-4

Constant light in early life induces fear-related behavior in chickens with suppressed melatonin secretion and disrupted hippocampal expression of clock- and BDNF-associated genes

J Anim Sci Biotechnol. 2022 Jun 21;13(1):67. doi: 10.1186/s40104-022-00720-4.

Authors

Yang Yang^{1

2}, Wei Cong^{1

2}, Jie Liu^{1

2}, Mindie Zhao^{1

2}, Peirong Xu^{1

2}, Wanwan Han^{1

2}, Deyun Wang^{1

3}, Ruqian Zhao^{4

5}

Affiliations

¹ MOE Joint International Research Laboratory of Animal Health & Food Safety, Institute of Immunology, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
² Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
³ Institute of Traditional Chinese Veterinary Medicine, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
⁴ MOE Joint International Research Laboratory of Animal Health & Food Safety, Institute of Immunology, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. zhaoruqian@njau.edu.cn.
⁵ Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. zhaoruqian@njau.edu.cn.

Abstract

Background: 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.

Results: 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.

Conclusions: 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.

Keywords: BDNF/ERK; Constant light; Fear-related behavior; Hippocampus.

Abstract

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