Comparing Physiology, Behaviour and Hippocampal Gene Expression in Laying Hens Housing in Differing Experimental Housing Conditions, and that Exhibited Different Housing Preferences

Design of the
housing environment and resources provided may influence the long-term welfare
of commercial laying hens. Accessing nest boxes, perches and foraging materials
appears to be a behavioural priority for hens, but whether the quality of each
alternative is important to their overall experience is unclear. For this
reason, hens were housed in an environment that was designed to be “Preferred”
(P; n = 15) or “Non-Preferred” (NP; n = 15) for 26 weeks. P pens were large and
had deep wood shavings as litter, while NP pens were smaller and had a wire
floor. P pens contained more expansive nest boxes and perches than those in the
NP pens, along with a peat/sand mix dust bath which was absent from the NP
housing. P hens were also given daily positive reinforcers (e.g. food treats),
while NP hens experienced negative reinforcers (e.g. water spray). At the end
of the housing period, a range of physiological and behavioural measures were
taken, and birds were given a series of two-way preference tests between their
experimental housing (either P or NP) and a housing environment intermediate to
both conditions. Tissue was collected from the HF, and the expression of mRNA
transcripts for a range of candidate genes relating to adult hippocampal
neurogenesis (AHN) and glucocorticoid regulation was measured using
quantitative PCR. Preference for the experimental housing relative to the
intermediate conditions was significantly higher for birds housed in P than in
NP conditions. However, no other measure differentiated between hens housed in
the two conditions. A minority of birds from each condition made the unexpected
choice, and serum corticosterone was higher in these individuals than in hens
that made the majority choice. In the caudal HF, expression of doublecortin (DCX) mRNA was also lower in hens that
made the minority choice. The MR/GR mRNA ratio was lower in the rostral
HF of NP housed hens that made the minority choice (in favour of the NP
conditions), which might suggest that this subgroup of birds was the most
stressed. Expression of proliferative marker PCNA was higher in hens that chose the intermediate conditions over
either experimental housing condition. The validity of transcription as a proxy
for AHN in chickens is currently uncertain, and consistency between qPCR assays
was lower when cDNA came from different reverse transcriptions. However, the
existing and novel measures of experience both suggest that variation between
individuals, reflected by their preferences, may exceed differences arising
from an inanimate housing environment designed to be relatively positive or
negative for welfare. Work was approved by the University of Bristol Animal
Welfare and Ethical Review Body and conducted under U.K. Home Office Licences
(PPL: 30/2779 and 30/3392). Animal use and care was in accordance with the
Animals (Scientific Procedures) Act 1986, EU directive 2010/63/EU and the UK
Home Office code of practice for the housing and care of animals bred, supplied
or used for scientific purposes. Collection and post-mortem analysis of tissue
was approved by the Animal Welfare and Ethical Review Body at Newcastle
University (Project ID #549).

本研究的目的是探讨住宅环境及所提供资源的配置如何影响商业产蛋鸡的长期福利。鸡群在获取巢箱、栖架和觅食材料方面似乎表现出行为上的优先级，然而，每种替代方案的质量是否对其整体体验至关重要尚不明确。因此，将鸡群置于一种被设计为“首选”（P；n=15）或“非首选”（NP；n=15）的环境中饲养26周。P舍宽敞，铺有深层木屑作为垫料，而NP舍较小，地面为金属网。P舍比NP舍拥有更多宽敞的巢箱和栖架，以及一种泥炭/沙混合的尘埃浴，而NP舍则无。P鸡每天还会得到正面的强化物（例如食物奖励），而NP鸡则经历负面的强化物（例如水喷溅）。在饲养周期结束时，对生理和行为指标进行了多种测量，并对鸟类进行了实验性住宅（P或NP）与介于两种条件之间的住宅环境之间的双向偏好测试。从海马区收集组织，并使用定量PCR技术测量了与成年海马神经发生（AHN）和糖皮质激素调节相关的候选基因mRNA转录本的表达。与中间条件相比，饲养在P条件下的鸟类对实验性住宅的偏好显著更高。然而，没有其他指标能区分两种条件下的鸡。每个条件中都有少数鸟类做出了意外的选择，而这些个体的血清皮质酮水平高于做出多数选择的鸡。在尾端海马区，做出少数选择的鸡的双皮质素（DCX）mRNA表达也较低。NP饲养的鸡在鼻端海马区的MR/GR mRNA比率较低（有利于NP条件），这可能表明这一群体中的鸟类压力最大。选择中间条件而非任何实验性住宅条件的鸡中，增殖标记PCNA的表达更高。目前，转录作为鸡AHN代理的有效性尚不确定，当cDNA来自不同的逆转录时，qPCR检测的一致性较低。然而，现有和新的经验度量均表明，个体之间的差异，通过其偏好反映出来，可能超过由旨在相对积极或消极影响福利的无生命住宅环境引起的差异。本研究经布里斯托尔大学动物福利与伦理审查委员会批准，并在英国内政部许可证（PPL：30/2779和30/3392）下进行。动物的使用和照料符合1986年《动物（科学程序）法案》、欧盟指令2010/63/EU以及英国内政部关于饲养、供应或用于科学目的的动物照料实践指南。组织收集和尸检分析经纽卡斯尔大学动物福利与伦理审查委员会批准（项目ID #549）。