Emotion and Cognition Group, Department of Farm Animal Health, Utrecht University, the Netherlands.
J Anim Sci. 2013 Jan;91(1):137-46. doi: 10.2527/jas.2012-5227. Epub 2012 Oct 9.
Feather pecking and cannibalism in farm-kept laying hens are damaging behaviors both in terms of animal welfare and economic loss, and a major challenge in modern poultry farming. Both rearing with a foster hen and genetic selection have been demonstrated to reduce feather pecking in laying hens. We examined the effects of rearing with a foster hen, genetic selection for low mortality from cannibalism, and interactions between both, using cellular morphology and levels of the rate-limiting enzyme in dopamine production, tyrosine hydroxylase, in the hippocampus and nidopallium caudolaterale (NCL) as a potential measure for laying hen welfare. Hens from the second generation of a sib-selection scheme line derived from a pure-bred White Leghorn line, selected for low mortality and for production characteristics, or their control line (CL) selected only for production characteristics, were housed with or without a foster Silky hen for the first 7 wk of life. Aside from the presence or absence of a foster Silky hen during the first 7 wk of life, housing conditions were identical for all hens. The hens were then sacrificed and brains were removed at 52 wk of age. Brains were sectioned and stained using a Nissl staining to reveal cell soma morphology, or using immunocytochemistry for tyrosine hydroxlase. A greater degree of lateralization in the hippocampus was observed in hens reared without a foster hen, as measured by absolute difference in cell soma size between hemispheres (P<0.05). The low mortality line showed decreased concentrations of tyrosine hydroxylase in the NCL compared with the CL (P<0.005). Our results indicate that morphological changes in brain induced in very early life can be detected in adult hens, and that genetic selection against mortality due to cannibalism impacts tyrosine hydroxylase in the NCL of laying hens. These observations strengthen the notion that brain measures may be useful as potential readouts for animal welfare.
在农场饲养的蛋鸡中，啄羽和同类相食是两种具有破坏性的行为，既影响动物福利，又造成经济损失，也是现代家禽养殖面临的主要挑战。通过寄养母鸡和遗传选择来减少蛋鸡啄羽的方法已得到证实。我们利用细胞形态学和多巴胺生成限速酶酪氨酸羟化酶的水平，研究了在蛋鸡中利用寄养母鸡、遗传选择低同类相食死亡率以及两者相互作用的效果，以此作为评估蛋鸡福利的潜在指标。我们从一个纯系白来航鸡系中选择了第二代同系选择系，该系通过选择低死亡率和生产特征进行选育，或者仅选择生产特征的对照系（CL），这些母鸡在生命的前 7 周与或不与寄养的丝毛母鸡一起饲养。除了前 7 周是否有寄养的丝毛母鸡外，所有母鸡的饲养条件都是相同的。然后，在 52 周龄时将母鸡处死并取出大脑。用尼氏染色法对大脑进行切片和染色，以显示细胞体形态，或用酪氨酸羟化酶免疫细胞化学染色。与没有寄养母鸡的母鸡相比，饲养母鸡的大脑海马体的侧化程度更高，这通过两个半球之间的细胞体大小的绝对差异来衡量（P<0.05）。与对照系（CL）相比，低死亡率系的 NCL 中的酪氨酸羟化酶浓度降低（P<0.005）。我们的结果表明，在非常早期的生命中诱导的大脑形态变化可以在成年母鸡中检测到，并且对由于同类相食导致的死亡率进行遗传选择会影响蛋鸡 NCL 中的酪氨酸羟化酶。这些观察结果加强了这样一种观点，即大脑测量值可能作为动物福利的潜在指标有用。
