Behavioral Physiology of Livestock, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany.
Equine Economics, Faculty Agriculture, Economics and Management, Nuertingen-Geislingen University, Nuertingen, Germany.
PLoS One. 2022 Aug 17;17(8):e0272445. doi: 10.1371/journal.pone.0272445. eCollection 2022.
Domestic horses are currently often subject to management practices that can entail social stressors, which in turn can negatively influence immunocompetence and disease susceptibility. The present study therefore aimed to characterize the number of various blood leukocyte subsets in horses, focusing on two potentially stressful housing environments: changes in group composition and relocation to individual stabling. Immune measurements were conducted before as well as one and eight days after changes were made. They were complemented by an assessment of plasma cortisol concentrations as well as behavioral observations. One and eight days after relocation to single housing, the mean numbers of eosinophils, T helper cells and cytotoxic T cells decreased by up to 31%, 20% and 22% respectively, whereas the mean numbers of neutrophils increased by 25%. In contrast, one and eight days after changes in group composition not only the mean number of neutrophils, but also of monocytes, T helper cells and cytotoxic T cells increased by up to 24%, 17%, 9%, and 15% respectively. In consequence, an increase in the neutrophil-to-lymphocyte ratio indicating stress-induced immune modulation was found after relocation to single housing, but not after changes in group composition. The changes in leukocyte numbers after relocation to single housing were accompanied by a transient increase in cortisol concentrations after one day and the occurrence of disturbed behavior patterns one week after change in housing condition. In contrast, changes in group composition did not result in an increase of cortisol concentrations or in an increase of aggressive interactions. The results strongly indicate that individual stabling is an intense stressor leading to acute and lasting alterations in blood counts of various leukocyte types. The study highlights a probable negative impact of single housing on welfare and health of horses and an advantage of group housing systems in view of immunocompetence.
目前，家养马通常受到管理措施的影响，这些措施可能会带来社会压力源，从而对免疫能力和疾病易感性产生负面影响。因此，本研究旨在描述马的各种血液白细胞亚群的数量，重点关注两种潜在的应激性饲养环境：群体组成的变化和搬迁到单独的畜栏。在进行免疫测量之前以及在进行变化后的第 1 天和第 8 天进行了免疫测量。同时还评估了血浆皮质醇浓度以及行为观察。搬迁到单独的畜栏后第 1 天和第 8 天，嗜酸性粒细胞、辅助性 T 细胞和细胞毒性 T 细胞的平均数量分别下降了 31%、20%和 22%，而中性粒细胞的平均数量增加了 25%。相比之下，群体组成变化后的第 1 天和第 8 天，不仅中性粒细胞的平均数量，而且单核细胞、辅助性 T 细胞和细胞毒性 T 细胞的平均数量也分别增加了 24%、17%、9%和 15%。因此，在搬迁到单独的畜栏后，发现中性粒细胞与淋巴细胞比值增加，表明应激引起的免疫调节，但在群体组成变化后则没有。搬迁到单独的畜栏后白细胞数量的变化伴随着皮质醇浓度在第 1 天短暂增加和在改变畜栏条件后的第 1 周出现行为模式紊乱。相比之下，群体组成的变化并没有导致皮质醇浓度的增加或攻击性互动的增加。研究结果强烈表明，单独的畜栏是一种强烈的应激源，会导致各种白细胞类型的血液计数发生急性和持久的变化。该研究强调了单独畜栏对马的福利和健康可能产生负面影响，以及群体畜栏系统在免疫能力方面的优势。
