Sherbrooke Research and Development Centre, Agriculture and Agri-food Canada, 2000 College Street, Sherbrooke, Québec, Canada, J1M 1Z3; Population Medicine, Ontario Veterinary College, University of Guelph, Gordon Street & College Avenue West, Guelph, Ontario, Canada, N1G 2W1.
Sherbrooke Research and Development Centre, Agriculture and Agri-food Canada, 2000 College Street, Sherbrooke, Québec, Canada, J1M 1Z3.
Physiol Behav. 2022 Oct 1;254:113898. doi: 10.1016/j.physbeh.2022.113898. Epub 2022 Jul 2.
The objective of this study was to describe the physiological response of gestating and lactating sows to naturally-occurring environmental conditions, and to identify factors that may contribute to or prevent heat stress, while being kept outdoors in Québec, Canada during the summer. Six groups of 4 Yorkshire-Landrace sows lived in outdoor pens equipped with a wallow, shade structure, farrowing huts and access to a pasture from July to September 2018. Between week 15 of gestation and week 3 of lactation (inclusive), we recorded the location of each sow 5 days/week during 5 daily 15-min observation periods, and additionally measured the sow's respiratory rate and mud cover at the end of each observation period. Simultaneously, we collected sow body temperature data with vaginal temperature loggers 24 h/d on week 15 of gestation and week 2 of lactation, and monitored environmental conditions with temperature and humidity loggers to calculate the temperature humidity index (THI). Sows had significantly higher and more variable body temperatures during lactation compared to gestation (P ≤ 0.0001), and when THI was analysed as a continuous variable, it was positively associated with sow body temperature during the night in lactation. During gestation, neither respiratory rate nor body temperature were associated with high or low levels of THI (P = 0.15 and 0.79, respectively) or mud cover (P = 0.29 and 0.94, respectively). However, in lactation, respiratory rate was higher when, simultaneously, THI exceeded 74 and mud cover was low (P = 0.006), while a THI higher than 74 and a low mud cover had independent effects on body temperature (P = 0.012 and 0.004, respectively). In lactation, sows that spent an entire observation period in the farrowing hut also had a higher respiratory rate than sows that left the hut at least once (P = 0.009). In summary, lactating sows were more likely to show increases in respiratory rate and body temperature in warmer conditions than gestating sows, and our findings also suggest that time in the farrowing hut may be a risk factor for heat stress. However, mud cover may limit these physiological consequences when sows have access to a wallow.
本研究的目的是描述妊娠和哺乳期母猪对自然环境条件的生理反应，并确定可能导致或预防热应激的因素，同时在加拿大魁北克省的夏季将它们饲养在户外。2018 年 7 月至 9 月期间，6 组约克夏-兰德瑞斯母猪生活在配备泥坑、遮荫结构、产仔棚和牧场通道的户外围栏中。在妊娠第 15 周到哺乳期第 3 周（含）期间，我们每周 5 天在每天 5 次每次 15 分钟的观察期内记录每头母猪的位置，并在每次观察结束时测量母猪的呼吸频率和泥覆盖面积。同时，我们使用阴道温度记录仪在妊娠第 15 周和哺乳期第 2 周每天 24 小时记录母猪的体温数据，并使用温度和湿度记录仪监测环境条件以计算温度湿度指数（THI）。与妊娠相比，哺乳期母猪的体温显著升高且变化更大（P≤0.0001），并且当将 THI 作为连续变量进行分析时，它与哺乳期夜间母猪体温呈正相关。在妊娠期间，呼吸率和体温均与高或低 THI 水平（P=0.15 和 0.79）或泥覆盖面积（P=0.29 和 0.94）无关。然而，在哺乳期，当 THI 超过 74 且泥覆盖面积低时，呼吸率更高（P=0.006），而 THI 高于 74 和泥覆盖面积低对体温有独立影响（P=0.012 和 0.004）。在哺乳期，整个观察期都在产仔棚中的母猪的呼吸率也高于至少离开一次棚的母猪（P=0.009）。总之，与妊娠母猪相比，哺乳期母猪在较温暖的条件下更有可能出现呼吸率和体温升高的情况，我们的研究结果还表明，在产仔棚中停留的时间可能是热应激的一个风险因素。然而，当母猪可以进入泥坑时，泥覆盖面积可能会限制这些生理后果。
