The metabolic heat production of modern pigs has increased by an average of 16%, compared with sows of 30 years ago. Therefore, it is likely that temperature recommendations require updating to meet the needs of modern pigs. The objective of this study was to evaluate whether different reproductive stages of sows altered thermal preference and if current recommendations required updating. Twenty multiparous sows (3.4 ± 1.2 parity) in different reproductive stages (nonpregnant: n = 7; mid-gestation: 58.5 ± 5.68 d, n = 6; and late-gestation: 104.7 ± 2.8 d, n = 7) were tested. Thermal preference was individually tested, and sows could freely choose a temperature, using a thermal gradient between 10.4 and 30.5 °C. Sows were given 24 h to acclimate to the thermal apparatus. Before testing began, sows were given daily feed allotment and returned to the apparatus. Video from the 24-h test period was used to record sow behavior (time spent inactive), posture (upright and sternal and lateral lying), and location using instantaneous scan samples every 15 min. Data were analyzed using PROC MIXED procedure in SAS 9.4. A cubic regression model was used to calculate the sow’s most preferred temperature based on the location, or temperature, in which they spent the most time. The preference range was calculated using peak temperature preference ±SE for each sow. The reproductive stage altered where sows spent their time within the thermal gradient (P < 0.01). Late-gestation sows preferred cooler temperatures (14.0 °C) than mid-gestation (14.8 °C; P < 0.01) and nonpregnant sows (14.8 °C; P < 0.01). In summary, sow thermal preferences were within the lower half of the current recommended range (10 to 25 °C). This indicates that temperatures at the higher end of the recommended range could be uncomfortable to sows and that the thermal comfort zone of sows may be narrower than recommendations indicate.

中文翻译：

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母猪繁殖三个阶段的热偏好评估

与 30 年前的母猪相比，现代猪的代谢产热平均增加了 16%。因此，温度建议可能需要更新以满足现代猪的需求。本研究的目的是评估母猪的不同繁殖阶段是否会改变热偏好，以及当前的建议是否需要更新。测试了 20 头不同生殖阶段的经产母猪（3.4 ± 1.2 胎次）（非妊娠：n = 7；妊娠中期：58.5 ± 5.68 天，n = 6；妊娠晚期：104.7 ± 2.8 天，n = 7）。对热偏好进行了单独测试，母猪可以使用 10.4 到 30.5 °C 之间的热梯度自由选择温度。母猪被给予 24 小时以适应热力设备。在测试开始之前，每天给母猪分配饲料并送回设备。24 小时测试期间的视频用于记录母猪行为（不活动时间）、姿势（直立、胸骨和侧卧）和位置，每 15 分钟使用一次瞬时扫描样本。使用 SAS 9.4 中的 PROC MIXED 程序分析数据。三次回归模型用于根据母猪花费最多时间的位置或温度来计算母猪最喜欢的温度。偏好范围是使用每头母猪的峰值温度偏好±SE计算的。母猪在热梯度内度过的繁殖阶段发生了变化（P < 0.01）。与妊娠中期（14.8 °C；P < 0.01）和非妊娠母猪（14.8 °C；P < 0.01）相比，妊娠晚期母猪更喜欢凉爽的温度（14.0 °C）。总之，母猪的热偏好在当前推荐范围的下半部分（10 到 25 °C）。这表明，在推荐范围的较高端的温度可能会让母猪感到不舒服，并且母猪的热舒适区可能比推荐值更窄。