The goal of this experiment was to measure the physiological response of individual laying hens exposed to heat stress (HS). Performance, egg quality, body temperature (BT), and blood chemistry of laying hens were individually recorded before and after various intervals of daily cyclic HS. In total, 407 18-week-old W-36 parent-line laying hens (Hy-Line International, Dallas Center, IA) were housed individually in battery cages. After an acclimation period, baseline data were collected from 22 to 24-wk before the hens were subjected to a daily cyclic HS consisting of 7 h at 35°C returning to 30°C for the remaining 17 h/D from 24 to 28-wk of age. Eggs were collected and individually weighed daily. Feed intake (FI), egg production (EP), egg weights, egg mass, BW, and feed efficiency (FE) (g egg/kg FI) were calculated over 2-wk time periods. Eggs were collected for quality assessment the day before HS began, the 2nd day of HS, and on a weekly basis throughout the 4-wk HS. Blood was collected and BT measured the day before heat HS was initiated, on the first day of HS, and again at 2 and 4-wk of HS. Blood PCO2 and iCa decreased, and blood pH increased within 4 to 6 h of HS (P ≤ 0.01). Shell weights decreased with acute HS, possibly due to the reduction in blood iCa (P ≤ 0.01). After 4-wk of HS the blood pH returned to pre-HS levels but iCa remained decreased (P ≤ 0.01). Shell weights remained low and Haugh units decreased after 2 and 4-wk of HS (P ≤ 0.01). Feed efficiency was increased and FI, EP, and BW decreased by 2-wk of HS and remained low through 4-wk (P ≤ 0.01). The cyclic HS had a significant effect on the performance, egg quality, and blood chemistry over the 4-wk HS.

中文翻译：

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急性和慢性热应激对蛋鸡生产性能、蛋品质、体温和血气参数的影响。

本实验的目的是测量暴露于热应激 (HS) 的个体蛋鸡的生理反应。在每日循环 HS 的不同间隔之前和之后分别记录蛋鸡的性能、蛋质量、体温 (BT) 和血液化学。总共有 407 只 18 周大的 W-36 母系蛋鸡（Hy-Line International，达拉斯中心，IA）被单独饲养在电池笼中。在适应期后，在母鸡每天进行循环 HS 之前，从 22 到 24 周收集基线数据，该循环 HS 包括 7 小时在 35°C 返回到 30°C，其余 17 小时/天从 24 到 28-周岁。每天收集鸡蛋并单独称重。在 2 周的时间段内计算采食量 (FI)、产蛋量 (EP)、蛋重、蛋重、BW 和饲料效率 (FE) (g egg/kg FI)。在 HS 开始前一天、HS 的第二天以及整个 4 周 HS 中每周收集鸡蛋用于质量评估。在热 HS 开始的前一天、HS 的第一天以及 HS 的第 2 周和第 4 周再次采集血液并测量 BT。血 PCO2 和 iCa 降低，血液 pH 值在 HS 后 4 至 6 小时内升高（P ≤ 0.01）。壳重随着急性 HS 下降，可能是由于血液 iCa 减少（P ≤ 0.01）。HS 4 周后，血液 pH 值恢复到 HS 前水平，但 iCa 仍然下降（P ≤ 0.01）。在 HS 的 2 周和 4 周后，壳重仍然很低，哈夫单位下降（P ≤ 0.01）。饲料效率提高，FI、EP 和 BW 在 HS 的 2 周内下降，并在 4 周内保持较低水平（P ≤ 0.01）。与 4 周 HS 相比，循环 HS 对性能、卵质量和血液化学有显着影响。