Brown Austin A, Sobotik Eric B, House Gabrielle M, Nelson Jill R, Archer Gregory S
Department of Poultry Science, Texas A&M University, College Station, TX, United States.
Front Physiol. 2022 Aug 16;13:943471. doi: 10.3389/fphys.2022.943471. eCollection 2022.
Different commercial lines of laying hens may show varying levels of fearfulness in response to stressful events or situations. It is important to understand the differences in fear response and stress susceptibility. In this study, four commercial laying hen lines reared from hatch to 32 weeks of age in a cage free system Strains consisted of a brown egg laying line (Hyline Brown; HB) and three white egg laying lines (W36, W80, and LSL). Sixty hens from each strain were used. Each hen was assessed for fearfulness using the following tests: isolation (ISO), emergence (EMG), inversion (INV), and tonic immobility (TI). Stress was assessed based on physical asymmetry (ASYM), corticosterone (CORT) concentrations, and heterophil:lymphocyte ratio (HL). At 3 weeks of age, the W80 birds exhibited more vocalizations during ISO and a shorter duration to emerge than other lines except the HB birds during EMG. Conversely the W36 birds had fewer vocalizations during ISO and emerged quicker than other birds except the LSL during EMG. At 16 weeks of age, the LSL and the W36 bird demonstrated greater fear in TI than the HB. At 30 weeks of age, the observed fear response strategies of each strain changed from previous age and differences were observed between lines ( < 0.05). At both 16 and 30 weeks of age the HB birds had the highest ( < 0.05) stress indicators (CORT, HL, and ASYM). Furthermore, they had a higher CORT after acute stressor ( < 0.05). Commercial lines of laying hens show clear variation in their stress response strategy and stress susceptibility. Brown egg laying hens tend to actively avoid perceived threats whereas white egg laying hens use passive avoidance. Brown egg laying hens also have higher levels in the measures of stress susceptibility than white egg laying hens. Understanding of individual strain response to fearful stimuli and other stressors is important knowledge to appropriately determine welfare differences between strains of layers as the baseline measures are often different.
不同商业品系的蛋鸡在面对应激事件或情况时可能表现出不同程度的恐惧。了解恐惧反应和应激易感性的差异很重要。在本研究中，四个商业蛋鸡品系在无笼系统中从孵化饲养至32周龄。品系包括一个褐壳蛋鸡品系（海兰褐；HB）和三个白壳蛋鸡品系（W36、W80和LSL）。每个品系使用60只母鸡。使用以下测试评估每只母鸡的恐惧程度：隔离（ISO）、出笼（EMG）、翻转（INV）和强直性静止（TI）。基于身体不对称性（ASYM）、皮质酮（CORT）浓度和嗜异性粒细胞：淋巴细胞比率（HL）评估应激。在3周龄时，W80品系的鸡在ISO测试中发出更多叫声，并且在EMG测试中除HB品系的鸡外，比其他品系的鸡出笼时间更短。相反，W36品系的鸡在ISO测试中叫声较少，并且在EMG测试中除LSL品系的鸡外，比其他鸡出笼更快。在16周龄时，LSL品系和W36品系的鸡在TI测试中表现出比HB品系的鸡更大的恐惧。在30周龄时，每个品系观察到的恐惧反应策略与之前的年龄不同，并且品系间存在差异（P<0.05）。在16周龄和30周龄时，HB品系的鸡应激指标（CORT、HL和ASYM）最高（P<0.05）。此外，它们在急性应激源后CORT更高（P<0.05）。商业蛋鸡品系在应激反应策略和应激易感性方面表现出明显差异。褐壳蛋鸡倾向于主动避免感知到的威胁，而白壳蛋鸡则采用被动回避。褐壳蛋鸡在应激易感性指标方面也比白壳蛋鸡水平更高。了解各个品系对应激刺激和其他应激源的反应是重要的知识，以便在基线测量通常不同的情况下，适当地确定蛋鸡品系之间的福利差异。
