Iida Ryosuke, Piñeiro Carlos, Koketsu Yuzo
Department of Agriculture, School of Agriculture, Meiji University, Kanagawa 214-8571, Japan.
Department of Data Management and Analysis, PigCHAMP Pro Europa S.L., 40006 Segovia, Spain.
J Anim Sci. 2021 Jul 1;99(7). doi: 10.1093/jas/skab173.
High temperature is an environmental factor that impairs sow fertility. In this study, we identified the critical weeks for heat stress effects on aspects of fertility performance, namely weaning-to-first-service interval (WSI) and farrowing rate (FR). We also examined the threshold temperatures above which the fertility performance deteriorated and whether there were any differences between parities regarding heat stress effects or thresholds. Performance data of sows in 142 herds from 2011 to 2016 were matched to appropriate weekly averaged daily maximum temperatures (Tmax) from weather stations close to the herds. Two types of ratios (i.e., ratio for WSI and odds ratio for FR) were used to identify the critical weeks for heat stress by comparing the respective measures for two sow groups based on Tmax in different weeks around weaning or service events. The ratios for WSI were calculated between groups of sows exposed to Tmax ≥ 27 °C or <27 °C in each week before weaning, with the Tmax cutoff value based on a recent review study. Similarly, the odds ratios for FR for the two groups were calculated in weeks around service. The weeks with the largest differences in the fertility measures between the two Tmax groups (i.e., the highest ratio for WSI and the lowest odds ratio for FR) were considered to be the critical weeks for heat stress. Also, piecewise models with different breakpoints were constructed to identify the threshold Tmax in the critical week. The breakpoint in the best-fit model was considered to be the threshold Tmax. The highest ratios for WSI were obtained at 1 to 3 wk before weaning in parity 1 and 2 or higher sow groups. The threshold Tmax leading to prolonged WSI was 17 °C for parity 1 sows and 25 °C for parity 2 or higher sows. Increasing Tmax by 10 °C above these thresholds increased WSI by 0.65, and 0.33 to 0.35 d, respectively (P < 0.01). For FR, the lowest odds ratios were obtained at 2 to 3 wk before service in parity 0, 1, and 2 or higher sow groups. The threshold Tmax leading to reductions in FR was 20, 21, and 24 to 25 °C for parity 0, 1, and 2 or higher sow groups, respectively. Increasing Tmax by 10 °C above these thresholds decreased FR by 3.0%, 4.3%, and 1.9% to 2.8%, respectively (P < 0.01). These results indicate that the critical weeks for heat stress were 2 to 3 wk before service for FR and 1 to 3 wk before weaning for WSI. The decreases in fertility performance in parity 0 to 1 sows started at temperatures 3 to 8 °C lower than in parity 2 or higher sows.
高温是损害母猪繁殖力的一个环境因素。在本研究中，我们确定了热应激对繁殖性能各方面产生影响的关键周数，即断奶至首次配种间隔（WSI）和产仔率（FR）。我们还研究了繁殖性能开始恶化时的临界温度，以及不同胎次在热应激影响或临界温度方面是否存在差异。将2011年至2016年142个猪群中母猪的性能数据与各猪群附近气象站每周平均每日最高温度（Tmax）进行匹配。通过比较断奶或配种事件前后不同周基于Tmax的两个母猪组的相应指标，使用两种类型的比率（即WSI比率和FR优势比）来确定热应激的关键周数。WSI比率是在断奶前每周暴露于Tmax≥27°C或<27°C的母猪组之间计算的，Tmax临界值基于最近的一项综述研究。同样，在配种前后的几周内计算两组的FR优势比。两个Tmax组之间繁殖指标差异最大的周数（即WSI最高比率和FR最低优势比）被认为是热应激的关键周数。此外，构建了具有不同断点的分段模型以确定关键周的临界Tmax。最佳拟合模型中的断点被视为临界Tmax。在第1胎和第2胎或更高胎次的母猪组中，断奶前1至3周获得了最高WSI比率。导致WSI延长的临界Tmax，第1胎母猪为17°C，第2胎或更高胎次母猪为25°C。高于这些临界值Tmax每升高10°C，WSI分别增加0.65天和0.33至0.35天（P<0.01）。对于FR，在第0胎、第1胎和第2胎或更高胎次的母猪组中，配种前2至3周获得了最低优势比。导致FR降低的临界Tmax，第0胎母猪为20°C，第1胎母猪为21°C，第2胎或更高胎次母猪为24至25°C。高于这些临界值Tmax每升高10°C，FR分别降低3.0%、4.3%和1.9%至2.8%（P<0.01）。这些结果表明，热应激的关键周数对于FR是配种前2至3周，对于WSI是断奶前1至3周。第0至1胎母猪繁殖性能下降开始时的温度比第2胎或更高胎次母猪低3至8°C。
