Evaluation of heat stress effects on production traits and somatic cell score of Holsteins in a temperate environment
Evaluation of heat stress effects on production traits and somatic cell score of Holsteins in a temperate environment
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DOI：
10.3168/jds.2012-5947
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发表时间：
2013-03-01
影响因子：
3.5
通讯作者：
Gengler, N.
中科院分区：
文献类型：
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作者：
Hammami, H.;Bormann, J.;Gengler, N.
本研究旨在评估大陆性温带气候下荷斯坦牛所表现出的热应激程度。 2000 年至 2011 年间从 604 个牛群的 23,963 头奶牛收集的牛奶、脂肪、蛋白质和体细胞计数测试日记录与卢森堡 14 个公共气象站的气象数据相结合。通过对 24 小时内每小时 TI 进行平均，计算出根据温度、相对湿度、太阳辐射和风速加权的 6 种不同热指数 (TI) 的日值。热应激阈值首先通过折线回归模型确定。此后应用回归模型来量化热应激导致的牛奶产量损失。有效确定了牛奶和蛋白质产量下降的临界点。对于脂肪产量，没有为任何研究的 TI 确定有效阈值。随着 TI 值的增加，每日脂肪产量趋于稳定下降。每日体细胞评分模式的特点是最低和最高 TI 范围内的值均增加，表观温度指数对冷应激的反应更为明显。 TI 和性状之间的阈值不同。对于生产性状，温湿度指数（THI）范围为 62（TI1）至 80（TI3），表观温度指数范围为 16（TI5）至 20（TI6）。相应的体细胞评分阈值较高，范围分别为 66 (TI1) 至 82 (TI3) 和 20 (TI5) 至 23 (TI6)。使用传统 Till (TI1) 时，观察到每单位轻度、中度和极端热应激水平的最大产奶量下降分别为 0.164、0.356 和 0.955 kg。 TI2（根据风速和太阳辐射调整的 Till 指数）检测到，每年牛奶、脂肪和蛋白质损失最高，分别为 54、5.7 和 4.2 公斤。后一个指数可以被认为是热应激的最佳指标，可用于温带地区在预期气候变化下的预测和牛群管理的第一步。
This study was aimed to evaluate the degree of thermal stress exhibited by Holsteins under a continental temperate climate. Milk, fat, protein, and somatic cell count test-day records collected between 2000 and 2011 from 23,963 cows in 604 herds were combined with meteorological data from 14 public weather stations in Luxembourg. Daily values of 6 different thermal indices (TI) weighted in term of temperature, relative humidity, solar radiation, and wind speed were calculated by averaging hourly TI over 24 h. Heat stress thresholds were first identified by a broken-line regression model. Regression models were thereafter applied to quantify milk production losses due to heat stress. The tipping points at which milk and protein yields declined were effectively identified. For fat yield, no valid threshold was identified for any of the studied TI. Daily fat yields tended to decrease steadily with increasing values of TI. Daily somatic cell score patterns were marked by increased values at both lowest and highest TI ranges, with a more pronounced reaction to cold stress for apparent temperature indices. Thresholds differed between TI and traits. For production traits, they ranged from 62 (TI1) to 80 (TI3) for temperature-humidity indices (THI) and from 16 (TI5) to 20 (TI6) for apparent temperature indices. Corresponding somatic cell score thresholds were higher and ranged from 66 (TI1) to 82 (TI3) and from 20 (TI5) to 23 (TI6), respectively. The largest milk decline per unit of mild, moderate, and extreme heat stress levels of 0.164, 0.356, and 0.955 kg, respectively, was observed when using the conventional Till (TI1). The highest yearly milk, fat, and protein losses of 54, 5.7, and 4.2 kg, respectively, were detected by TI2, the Till index that is adjusted for wind speed and solar radiation. The latter index could be considered as the best indicator of heat stress to be used for forecast and herd Management in a first step in temperate regions under anticipated climate changes.