Institute of Behavioural Physiology, Research Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Institute of Behavioural Physiology, Research Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Animal. 2022 Apr;16(4):100495. doi: 10.1016/j.animal.2022.100495. Epub 2022 Mar 23.
Hair cortisol concentration (HCC) is used as an indicator of long-term stress or pathologies in humans and increasingly in animals. Although the main mechanism for the incorporation of cortisol into the hair shaft is by diffusion from blood, cortisol may also be incorporated from external sources by contamination of the hair surface. In farm animals under conventional husbandry conditions and trapped animals, contamination of hair with cortisol-containing body fluids, especially with urine, was shown to be a considerable confounding factor when studying HCCs. We recently found that cattle and pigs exhibit elevated HCCs in distal hair segments and assume that the incorporation of external cortisol is facilitated in these older hair segments. Therefore, the aim of this study was to investigate the effects of urine contamination on HCC in different hair segments of pigs and cattle, and to determine whether different cleaning protocols can prevent contamination effects. In an in vivo experiment in pigs (n = 18) and an in vitro experiment in cattle (n = 12), hairs were repeatedly contaminated with urine of the respective species and then shaved or cut in segments. Cortisol concentrations in hair segments were analysed by enzyme immunoassay after washing with isopropanol and extraction with methanol. Results were compared with HCCs in untreated hairs or hairs treated with water. Moreover, additional bovine hair samples contaminated with urine were subjected to two further cleaning procedures. Contamination with urine generally increased HCCs, and it was demonstrated for the first time that this effect is more pronounced in distal compared to proximal hair segments in both species. The immersion of bovine hair in vitro in water caused a washout of cortisol, which was also more pronounced in distal hair segments. In general, the different cleaning protocols for cattle hair did not prevent contamination effects, so we assume that external cortisol not only adheres but is incorporated into the hair shaft. Structural damage of older, distal hair segments may facilitate permeability of the hair matrix and diffusion of cortisol from and into aqueous solutions. Thus, the validity of HCC as a marker of stress is compromised in animals where soiling of hair with body fluids is a risk factor. Therefore, hair samples should be collected from clean body regions and, if possible, using proximal hair segments.
毛发皮质醇浓度 (HCC) 被用作人类和动物中长期压力或病理的指标。尽管皮质醇纳入毛发的主要机制是通过从血液扩散，但皮质醇也可能通过毛发表面的污染从外部来源纳入。在常规养殖条件下的农场动物和被捕食的动物中，毛发被含有皮质醇的体液污染，尤其是尿液污染，被证明是研究 HCC 时一个相当大的混杂因素。我们最近发现，牛和猪在远端毛发段中表现出升高的 HCC，并假设外部皮质醇的纳入在这些较老的毛发段中更容易。因此，本研究的目的是调查尿液污染对猪和牛不同毛发段 HCC 的影响，并确定不同的清洁方案是否可以防止污染影响。在猪的体内实验（n = 18）和牛的体外实验（n = 12）中，毛发反复被各自物种的尿液污染，然后刮毛或分段切割。用异丙醇洗涤和甲醇提取后，通过酶免疫分析测定毛发段中的皮质醇浓度。结果与未处理毛发或用水处理毛发的 HCC 进行比较。此外，还对另外污染有尿液的牛毛样本进行了另外两种清洁程序。尿液污染一般会增加 HCC，这是首次在两个物种中，远端毛发段比近端毛发段表现出更明显的效果。牛的体外毛发浸入水中会导致皮质醇的冲洗，在远端毛发段中更为明显。一般来说，牛毛的不同清洁方案并没有防止污染影响，因此我们假设外部皮质醇不仅附着在毛发上，而且还纳入了毛发轴。较老、远端毛发段的结构损伤可能会增加毛发基质的通透性，并促进皮质醇从水溶液扩散到毛发中。因此，在毛发被体液污染是一个风险因素的动物中，HCC 作为压力标志物的有效性受到损害。因此，应从清洁的身体部位采集毛发样本，如果可能的话，使用近端毛发段。
