Atoui Ahlem, Najari Sghaier, Diaz Clara, Ramón Manuel, Ragab Mohamed, Laaroussi Aicha, Abdennebi Mouldi, Carabaño Maria Jesus
Laboratory of Livestock and Wildlife, Institute of Arid Regions (IRA), Medenine 4119, Tunisia.
Depto de Mejora Genética Animal, INIA-CSIC, Ctra de La Coruña Km 7.5, 28040 Madrid, Spain.
Animals (Basel). 2024 Oct 3;14(19):2846. doi: 10.3390/ani14192846.
This study evaluates the impact of thermal load on the weights of Tunisian local kids using 24 models with cubic and quadratic Legendre polynomials, based on daily temperatures (Tmin, Tmax, and Tavg) on the day of weight recording and averaged over 7, 14, and 21 days before weighing. The deviance information criterion (DIC) consistently shows that cubic polynomial models offer a better fit than quadratic models, highlighting their superior accuracy in studying the effects of thermal load on kid weights. The models with the best fit utilized average or maximum temperatures over 14 or 21 days. The patterns of response were similar across the temperature variables and periods, showing a stable weight response at lower temperatures (thermoneutral region) followed by a decline as the temperatures increased. The weight loss was -125 g/°C beyond the moderate heat stress threshold (Tavg21 = 17.7 °C) and -450 g/°C beyond the severe heat stress threshold (Tavg21 = 25.3 °C) for Tavg21. The heat stress thresholds for moderate heat stress (HS1) were 8.6 °C for Tmin14, 27.4 °C for Tmax14, and 18.6 °C for Tavg14; moreover, for acute heat stress (HS2), they were 17.2 °C for Tmin14, 32.4 °C for Tmax14, and 25.5 °C for Tavg14. High variability in individual responses was observed, with differences in the slope of response ranging from 2.0 kg/°C for moderate heat stress to around 3.0 kg/°C for severe heat stress for Tavg. The correlations between the weights under different temperatures were low, indicating that rankings based on weight could change with varying heat conditions. The animals with larger weight levels generally demonstrated better heat tolerance, and those with good heat tolerance under moderate conditions were also likely to have good tolerance under severe conditions.
本研究使用24个带有三次和二次勒让德多项式的模型，基于体重记录当天的每日温度（最低温度、最高温度和平均温度）以及称重前7天、14天和21天的平均温度，评估热负荷对突尼斯当地幼崽体重的影响。偏差信息准则（DIC）始终表明，三次多项式模型比二次模型拟合得更好，突出了它们在研究热负荷对幼崽体重影响方面的更高准确性。拟合最佳的模型使用了14天或21天的平均温度或最高温度。不同温度变量和时间段的响应模式相似，在较低温度（热中性区）下体重响应稳定，随后随着温度升高而下降。对于平均温度21天（Tavg21），超过中度热应激阈值（Tavg21 = 17.7°C）时体重减轻为-125克/°C，超过重度热应激阈值（Tavg21 = 25.3°C）时体重减轻为-450克/°C。对于最低温度14天（Tmin14），中度热应激（HS1）的热应激阈值为8.6°C；对于最高温度14天（Tmax14），为27.4°C；对于平均温度14天（Tavg14），为18.6°C；此外，对于急性热应激（HS2），Tmin14为17.2°C，Tmax14为32.4°C，Tavg14为25.5°C。观察到个体反应存在高度变异性，平均温度下，中度热应激的反应斜率差异为2.0千克/°C，重度热应激约为3.0千克/°C。不同温度下体重之间的相关性较低，表明基于体重的排名可能会随热条件的变化而改变。体重水平较高的动物通常表现出更好的耐热性，在中度条件下耐热性好的动物在重度条件下也可能具有良好的耐受性。
