National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China.
Guizhou Nayong Professor Workstation of China Agricultural University, Bijie, China.
J Anim Sci. 2020 Nov 1;98(11). doi: 10.1093/jas/skaa348.
Conditions in early life play profound and long-lasting effects on the welfare and adaptability to stress of chickens. This study aimed to explore the hypothesis that the provision of environmental complexity in early life improves birds' adaptive plasticity and ability to cope with a challenge later in life. It also tried to investigate the effect of the gut-brain axis by measuring behavior, stress hormone, gene expression, and gut microbiota. One-day-old chicks were split into 3 groups: (1) a barren environment (without enrichment items) group (BG, n = 40), (2) a litter materials group (LG, n = 40), and (3) a perches with litter materials group (PLG, n = 40). Then, enrichment items were removed and simulated as an environmental challenge at 31 to 53 d of age. Birds were subjected to a predator test at 42 d of age. In the environmental challenge, when compared with LG, PLG birds were characterized by decreased fearfulness, lower plasma corticosterone, improved gut microbial functions, lower relative mRNA expression of GR, and elevated mRNA expressions of stress-related genes CRH, BDNF, and NR2A in the hypothalamus (all P < 0.05). Unexpectedly, the opposite was true for the LG birds when compared with the BG (P < 0.05). Decreased plasma corticosterone and fearfulness were accompanied by altered hypothalamic gene mRNA expressions of BDNF, NR2A, GR, and CRH through the HPA axis in response to altered gut microbial compositions and functions. The findings suggest that gut microbiota may integrate fearfulness, plasma corticosterone, and gene expression in the hypothalamus to provide an insight into the gut-brain axis in chicks. In conclusion, having access to both perches and litter materials in early life allowed birds to cope better with a future challenge. Birds in perches and litter materials environment may have optimal development and adaptive plasticity through the gut-brain axis.
早期生活条件对鸡的福利和应激适应能力产生深远而持久的影响。本研究旨在探讨以下假设：即在早期生活中提供环境复杂性可以提高鸟类的适应可塑性和应对后期生活挑战的能力。本研究还试图通过测量行为、应激激素、基因表达和肠道微生物群来研究肠道-大脑轴的影响。将 1 日龄小鸡分为 3 组：（1）贫瘠环境（无富集物）组（BG，n=40），（2）垫料组（LG，n=40）和（3）带垫料栖木组（PLG，n=40）。然后，在 31 至 53 日龄时去除富集物并模拟环境挑战。在 42 日龄时对鸡进行捕食者测试。在环境挑战中，与 LG 相比，PLG 鸟类的特征是恐惧程度降低、血浆皮质酮降低、肠道微生物功能改善、GR 相对 mRNA 表达降低、下丘脑应激相关基因 CRH、BDNF 和 NR2A 的 mRNA 表达升高（均 P<0.05）。出乎意料的是，LG 鸟类与 BG 相比则相反（P<0.05）。血浆皮质酮和恐惧程度降低伴随着下丘脑 BDNF、NR2A、GR 和 CRH 基因 mRNA 表达的改变，这是通过 HPA 轴对肠道微生物组成和功能改变的反应。研究结果表明，肠道微生物群可能通过 HPA 轴整合恐惧、血浆皮质酮和下丘脑基因 mRNA 表达，为研究禽类肠道-大脑轴提供了新的视角。总之，早期生活中接触栖木和垫料可以使鸟类更好地应对未来的挑战。处于栖木和垫料环境中的鸟类可能通过肠道-大脑轴获得最佳的发育和适应可塑性。
