Tetel V, Tonissen S, Fraley G S
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, United States.
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, United States.
Gen Comp Endocrinol. 2022 Feb 1;317:113975. doi: 10.1016/j.ygcen.2021.113975. Epub 2022 Jan 4.
It is becoming more common for poultry scientists to utilize direct and indirect measures of stress hormones to monitor bird welfare. However, it has been clear that our understanding of the avian hypothalamic-pituitaryadrenal axis (HPA) is insufficient as evidenced by the many conflicting reports regarding stress responses, such as transportation stress, in poultry. It has long been assumed that the poultry HPA functions similarly to that of mammals, but now we know that there are considerable differences in the avian HPA compared to mammals. Synthesis and release of glucocorticoids (GC) are stimulated by adrenocorticotropin hormone (ACTH); GC are synthesized from a common pathway that begins with cholesterol and pregnenolone. The synthesis of one of the glucocorticoids does not depend upon the synthesis of the other. The purpose of our study was to test the hypothesis that ACTH will stimulate both corticosterone and cortisol release in ducks. To test this hypothesis, we injected artificial ACTH (cosyntropin; 0.0625 mg/kg, 0.031 mg/kg, or 0.016 mg/kg or saline as control) intramuscularly into adult drakes and hens (N = 10/sex/dose). Both glucocorticoids (GC) were assayed in serum using previously verified ELISAs. Blood smears were also assessed for heterophil to lymphocyte ratios (HLR). Data were analyzed by repeated measures 3-way ANOVA with Fishers PLSD as an ad hoc test. We observed that both GC were secreted in significantly (p = 0.0002) different patterns in a dose-dependent manner compared to controls, and that there was a significant (p = 0.0001) sex difference in both GC compared to saline controls. Further, we observed that all doses of ACTH elicited a significant (p = 0.004) sex difference in the HLR response compared to controls, but no dose-dependent effects were noted. Our data suggest that ducks, at least, may utilize more than just corticosterone to maintain physiological homeostasis in response to stress. Further, the time course of the stressor to release GC and subsequent HLR response may be dependent upon sex. More detailed analyses of the HPA are necessary in all avian species to better understand stress responses as we utilize biological bases for welfare assessments and stress responses.
家禽科学家利用应激激素的直接和间接测量方法来监测禽类福利的情况越来越普遍。然而，很明显我们对鸟类下丘脑 - 垂体 - 肾上腺轴（HPA）的了解并不充分，这一点从关于家禽应激反应（如运输应激）的众多相互矛盾的报告中可见一斑。长期以来人们一直认为家禽的HPA功能与哺乳动物相似，但现在我们知道与哺乳动物相比，鸟类的HPA存在相当大的差异。糖皮质激素（GC）的合成和释放受促肾上腺皮质激素（ACTH）刺激；GC由一条从胆固醇和孕烯醇酮开始的共同途径合成。一种糖皮质激素的合成并不依赖于另一种的合成。我们研究的目的是检验ACTH会刺激鸭子同时释放皮质酮和皮质醇这一假设。为了验证这一假设，我们给成年公鸭和母鸡（每种性别/剂量组N = 10）肌肉注射人工合成的ACTH（促肾上腺皮质激素；0.0625mg/kg、0.031mg/kg或0.016mg/kg，或作为对照的生理盐水）。使用先前验证过的酶联免疫吸附测定法（ELISA）检测血清中的两种糖皮质激素（GC）。还评估了血涂片的嗜异性粒细胞与淋巴细胞比例（HLR）。数据通过重复测量三因素方差分析，并使用Fisher最小显著差异法（PLSD）作为事后检验进行分析。我们观察到与对照组相比，两种GC均以剂量依赖性方式呈现出显著不同（p = 0.0002）的分泌模式，并且与生理盐水对照组相比，两种GC均存在显著（p = 0.0001）的性别差异。此外，我们观察到与对照组相比，所有剂量的ACTH在HLR反应中均引发了显著（p = 0.004）的性别差异，但未观察到剂量依赖性效应。我们的数据表明，至少鸭子可能不仅仅利用皮质酮来维持对应激的生理稳态。此外，应激源释放GC和随后的HLR反应的时间进程可能取决于性别。在所有鸟类物种中，有必要对HPA进行更详细的分析，以便在我们将生物学基础用于福利评估和应激反应时更好地理解应激反应。
