[Effect of thermal manipulation during incubation on the hematological variables, serum biochemistry and morphometry of cloacal bursa of Japanese quails submitted to chronic heat stress]

ABSTRACT The objective of this study was to evaluate the effects of manipulation of the incubation temperature on the immune response of quails challenged thermally after hatching. For this, 540 eggs were distributed in three incubators, with temperature of 37.8°C and 60% humidity. From the 6th day of incubation to hatching the temperatures were adjusted to 37.8°C (standard), 38.5°C (intermediate) and 39.5°C (high). After hatching the quails were weighed and distributed in a completely randomized design with three incubation temperatures (37.8, 38.5 and 39.5°C) and two ambient temperatures (stress and thermoneutral). At 10, 20, 30 and 40 days four quail per treatment were euthanized to collect the cloacal burse, liver and heart to determine the absolute weight (g), relative weight (%) and area of the bursal follicles. Blood was sampled for determination of hemogram, leukogram and serum biochemistry. The data were analyzed and the differences between the means were determined by the Tukey test at 5%. Heat stress from 20 days onwards promotes a reduction in the absolute weight of the liver, heart, cloacal sac and in the area of the follicles. In addition, there was heterofilia, lymphopenia and increased heterophile/lymphocyte ratio. In conclusion, heat stress after 10 days of age can cause immunosuppression.

摘要 本研究旨在探讨孵化期温度调控对出雏后遭受热应激的鹌鹑免疫应答的影响。为此，将540枚鹌鹑蛋分配至3台孵化器中，初始孵化温度设定为37.8℃、相对湿度60%。自孵化第6天至出雏阶段，将孵化器温度分别调整为37.8℃（标准组）、38.5℃（中温组）与39.5℃（高温组）。出雏后，对鹌鹑称重，并采用完全随机设计进行分组，设置3种孵化温度（37.8、38.5、39.5℃）与2种环境温度（热应激组与热中性组）。分别于出雏后第10、20、30、40天，对每个处理组的4只鹌鹑实施安乐死，采集腔上囊（cloacal bursa）、肝脏与心脏，测定其绝对重量（g）、相对重量（%）以及法氏囊滤泡面积。采集血液样本以检测血常规、白细胞分类计数及血清生化指标。对所有数据进行统计分析，采用Tukey检验进行均值间差异比较，检验水准设为5%。研究结果显示，出雏后20天起施加热应激，可导致鹌鹑肝脏、心脏、腔上囊的绝对重量以及法氏囊滤泡面积显著降低；此外，可观察到异嗜性粒细胞增多、淋巴细胞减少以及异嗜性粒细胞/淋巴细胞比值升高。综上，鹌鹑出雏后10天起遭受热应激可引发免疫抑制。