Abstract Laying hens have undergone strong selection pressure for traits related to productivity in recent decades. This has led to an impressive increase in egg production but is also assumed to cause undesirable side effects, such as behavioural changes or increased bone damage. Resource trade-offs resulting from egg production might trigger such changes. Our hypothesis was that hens from lines selected for high levels of egg production need to conserve energy to maintain productivity by reducing locomotor activity. We further assumed that the reduced locomotor activity is accompanied by poorer motor coordination abilities. In addition to the performance level, phylogenetic origin has potential implications for behavioural and physiological differences. Thus, we compared hens from four purebred layer lines in a 2 × 2 model that differed in productivity levels (a line with high egg production (320 eggs/year) and a line with moderate egg production (200 eggs/year)) and phylogenetic origins (white and brown egg layer lines). Furthermore, hens of each line were kept in compartments of two different sizes (large, with stocking densities of 3.19 hens/m2; and small, with stocking densities of 5.94 hens/m2), to examine the effect of space and stocking density on the behaviour and bone strength of the hens. In total, we tested 742 chickens from the four different layer lines. We recorded their general locomotor activity in their home compartments and tested their motor coordination using a rotarod test. After the laying period, we examined the bone breaking strength of the tibiotarsi and the humeri from chickens of all four lines. The hens from both highly productive lines possessed poorer motor coordination than the hens from the moderately productive lines of corresponding phylogenetic origin. Furthermore, the hens from the brown egg-laying lines performed better than the hens from the white egg-laying lines. Compartment size had a positive effect on the motor coordination of the hens from the moderately productive lines and interacted with productivity. However, general locomotor activities were not different between the hens from lines with different productivities or of different phylogenetic origins. The hens from the moderately productive lines possessed higher bone breaking strengths than the hens from the highly productive lines within the phylogenetic groups. Our results show that the hens from the lines with high productivity have poorer motor coordination and lower bone breaking strength than the hens with moderate productivity. These results can help to gain further understanding of practical problems, such as the high prevalence of bone damage in laying hens.

中文翻译：

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运动中的鸡：产蛋水平和围栏大小对蛋鸡运动能力和骨骼稳定性的影响（Gallus gallus formadomadomica）

摘要 近几十年来，蛋鸡在与生产力相关的性状方面承受了很大的选择压力。这导致产蛋量显着增加，但也被认为会引起不良副作用，例如行为改变或骨骼损伤增加。鸡蛋生产导致的资源权衡可能会引发此类变化。我们的假设是，选择高产蛋品系的母鸡需要通过减少运动活动来保存能量以保持生产力。我们进一步假设运动活动的减少伴随着较差的运动协调能力。除了性能水平外，系统发育起源对行为和生理差异有潜在影响。因此，我们在 2 × 2 模型中比较了来自四个纯种蛋鸡品系的母鸡，这些母鸡的生产力水平不同（产蛋量高的品系（320 个蛋/年）和产蛋量中等的品系（200 个蛋/年））和系统发育起源（白色和棕色鸡蛋层线）。此外，每条线的母鸡被饲养在两种不同大小的隔间中（大，放养密度为 3.19 只母鸡/平方米；小，放养密度为 5.94 只/平方米），以检查空间和放养密度对母鸡的行为和骨骼强度。我们总共测试了来自四个不同层系的 742 只鸡。我们在他们的家庭隔间中记录了他们的一般运动活动，并使用旋转棒测试测试了他们的运动协调性。产卵期过后，我们检查了所有四系鸡的胫骨和肱骨的断骨强度。来自两个高产品系的母鸡比来自相应系统发育起源的中等生产品系的母鸡具有较差的运动协调性。此外，棕色产蛋系的母鸡比白色产蛋系的母鸡表现更好。隔间大小对来自中等生产线的母鸡的运动协调有积极影响，并与生产力相互作用。然而，来自具有不同生产力或不同系统发育起源的品系的母鸡之间的一般运动活动没有差异。来自中等生产力品系的母鸡比来自系统发育组中高生产力品系的母鸡具有更高的骨断裂强度。我们的结果表明，与中等生产力的母鸡相比，来自高生产力品系的母鸡的运动协调性较差，骨断裂强度较低。这些结果有助于进一步了解实际问题，例如蛋鸡骨损伤的高发率。