Heat stress (HS) affects the production performance in chickens and causes economic loss to the producers. Most of the studies have been conducted on and for the welfare of broilers. We still lack information on the physiological parameters being affected during chronic heat stress in layers. To fill this gap, the present study evaluated the effect of heat stress (induced in the chamber) during the prelaying period (21–23 weeks) on plasma levels of the hormones leptin and ghrelin and GH and expression of the respective receptors and heat stress markers. Three groups were considered, one at room temperature (CR) and the other two groups (SH and CH) subjected to heat stress at 39°C for four hours for three weeks (21–23 weeks of age). The SH group (SH) feed was supplemented with fermented yeast culture (FYC, 700 mg/kg), whereas the CH group was devoid of it. After that, all the groups were shifted to shed under natural ambient conditions till 31 weeks of age. Studies were restricted to production performance only. Feed offered without yeast culture (CH group) had a smaller concentration of plasma hormones () and increased expression fold of the hormone receptors (). Further, the group also presented higher liver AMP kinase enzyme, plasma MDA (malondialdehyde), and cholesterol concentrations. These changes likely explained the decrease in feed intake and the CH group’s body weight and further reduced the production performance during the laying period. Supplementation with FYC to birds had an opposite effect on the above-mentioned parameters, reducing HS effects. In summary, supplementation with FYC (700 mg/kg) maintained physiological parameters as in the CR group under HS conditions and negated adverse effects on parameters both before and during laying periods.

中文翻译：

---

补充发酵酵母培养物对荷尔蒙及其受体对暴露于较高温度和暴露后尼科巴里鸡生产性能的影响

热应激（HS）影响鸡的生产性能并给生产者造成经济损失。大多数研究都是为了肉鸡的福利而进行的。我们仍然缺乏关于在层间慢性热应激期间受到影响的生理参数的信息。为了填补这一空白，本研究评估了产蛋前（21-23 周）热应激（在室内诱导）对瘦素、生长素释放肽和 GH 的血浆水平以及相应受体和热应激的表达的影响标记。考虑了三组，一组在室温 (CR) 下，另外两组（SH 和 CH）在 39°C 下经受热应激 4 小时，持续三周（21-23 周龄）。SH组（SH）饲料中添加发酵酵母培养物（FYC，700 mg/kg），而CH组则没有。之后，所有组都在自然环境条件下转移到棚屋，直到31周龄。研究仅限于生产性能。未提供酵母培养物（CH 组）的饲料的血浆激素浓度较低（)和增加的激素受体表达倍数 (）。此外，该组还表现出较高的肝 AMP 激酶、血浆 MDA（丙二醛）和胆固醇浓度。这些变化可能解释了采食量和 CH 组体重的下降，并进一步降低了产蛋期间的生产性能。向鸟类补充 FYC 对上述参数有相反的影响，降低了 H2S 的影响。总之，在 HS 条件下，补充 FYC (700 mg/kg) 维持了 CR 组的生理参数，并在产蛋前和产蛋期间消除了对参数的不利影响。