The efficacy of an electric heat blanket (EHB) has previously been confirmed as an alternative method to evaluate heat stress (HS). However, a pair-feeding design has not been used with the EHB model. Therefore, study objectives were to determine the contribution of the nutritional plane to altered metabolism and productivity during EHB-induced HS. Multiparous Holstein cows (n = 18; 140 ± 10 d in milk) were subjected to 2 experimental periods (P); during P1 (4 d), cows were in thermoneutral conditions with ad libitum feed intake. During P2 (4 d), cows were assigned to 1 of 2 treatments: (1) thermoneutral conditions and pair-fed (PF; n = 8) or (2) EHB-induced HS with ad libitum feed intake (n = 10). Overall, the EHB increased rectal temperature, vaginal temperature, skin temperature, and respiration rate (1.4°C, 1.3°C, 0.8°C, and 42 breaths/min, respectively) relative to PF cows. The EHB reduced dry matter intake (DMI; 47%) and, by design, PF cows had a similar pattern and extent of decreased DMI. Milk yield decreased in EHB and PF cows by 27.3% (12.1 kg) and 13.4% (5.4 kg), respectively, indicating that reduced DMI accounted for only ∼50% of decreased milk synthesis. Milk fat content tended to increase (19%) in the EHB group, whereas in the PF cows it remained similar relative to P1. During P2, milk protein and lactose contents tended to decrease or decreased (1.3 and 2.2%, respectively) in both EHB and PF groups. Milk urea nitrogen remained unchanged in PF controls but increased (34.2%) in EHB cows relative to P1. The EHB decreased blood partial pressure of CO2, total CO2, HCO3, and base excess levels (17, 16, 17, and 81%, respectively) compared with those in PF cows. During P2, the EHB and PF cows had similar decreases (4%) in plasma glucose content, but no differences in circulating insulin were detected. However, a group by day interaction was detected for plasma nonesterified fatty acids; levels progressively increased in PF controls but remained unaltered in the EHB cows. Blood urea nitrogen increased in the EHB cows (61%) compared with the PF controls. In summary, utilizing the EHB model indicated that reduced nutrient intake explains only about 50% of the decrease in milk yield during HS, and the postabsorptive changes in nutrient partitioning are similar to those obtained in climate-controlled chamber studies. Consequently, the EHB is a reasonable and economically feasible model to study environmental physiology of dairy cows.

中文翻译：

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验证热应激模型：电热毯和营养面对泌乳奶牛的影响。

先前已经确认了电热毯（EHB）的功效，可以作为评估热应力（HS）的替代方法。但是，EHB模型尚未使用成对进纸设计。因此，研究目标是确定在EHB诱导的HS期间营养面对代谢和生产力改变的贡献。多头荷斯坦奶牛（n = 18；牛奶中140±10 d）进行了2个实验期（P）。在P1（4 d）期间，母牛处于热中性条件下，随意采食。在P2（4 d）期间，将母牛进行2种处理中的1种：（1）热中性条件和成对喂养（PF; n = 8）或（2）EHB诱导的HS，随意采食（n = 10） 。总体而言，EHB提高了直肠温度，阴道温度，皮肤温度和呼吸频率（1.4°C，1.3°C，0.8°C和42呼吸/分钟，相对于PF奶牛）。EHB减少了干物质摄入量（DMI； 47％），从设计上看，PF奶牛的DMI下降的模式和程度相似。EHB和PF奶牛的产奶量分别下降了27.3％（12.1 kg）和13.4％（5.4 kg），这表明DMI下降仅占牛奶合成下降的约50％。EHB组的牛奶脂肪含量倾向于增加（19％），而PF奶牛的脂肪含量与P1相似。在P2期间，EHB和PF组的牛奶蛋白和乳糖含量趋于减少或减少（分别为1.3％和2.2％）。PF对照组的牛奶尿素氮保持不变，但相对于P1，EHB奶牛的尿素氮增加（34.2％）。与PF母牛相比，EHB降低了CO2，总CO2，HCO3和基础过量水平（分别为17％，16％，17％和81％）的血液分压。在P2期间，EHB和PF奶牛的血浆葡萄糖含量下降相似（4％），但未发现循环胰岛素的差异。但是，检测到血浆非酯化脂肪酸之间存在逐日交互作用。PF对照的血红蛋白水平逐渐升高，但EHB奶牛的水平保持不变。与PF对照相比，EHB奶牛的血尿素氮增加（61％）。总而言之，利用EHB模型表明减少的养分摄入量仅解释了HS期间牛奶产量下降的约50％，并且养分分配后的吸收变化与在气候控制室研究中得出的相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。但未发现循环胰岛素的差异。但是，检测到血浆非酯化脂肪酸之间存在逐日交互作用。PF对照的血红蛋白水平逐渐升高，但EHB奶牛的水平保持不变。与PF对照相比，EHB奶牛的血尿素氮增加（61％）。总而言之，利用EHB模型表明减少的养分摄入量仅解释了HS期间牛奶产量下降的约50％，并且养分分配后的吸收变化与在气候控制室研究中得出的相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。但未发现循环胰岛素的差异。但是，检测到血浆非酯化脂肪酸之间存在逐日交互作用。PF对照的血红蛋白水平逐渐升高，但EHB奶牛的水平保持不变。与PF对照相比，EHB奶牛的血尿素氮增加（61％）。总而言之，利用EHB模型表明减少的养分摄入量仅解释了HS期间牛奶产量下降的约50％，并且养分分配后的吸收变化与在气候控制室研究中得出的相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。PF对照的血红蛋白水平逐渐升高，但EHB奶牛的水平保持不变。与PF对照相比，EHB奶牛的血尿素氮增加（61％）。总而言之，利用EHB模型表明减少的养分摄入量仅解释了HS期间牛奶产量下降的约50％，并且养分分配后的吸收变化与在气候控制室研究中得出的相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。PF对照的血红蛋白水平逐渐升高，但EHB奶牛的水平保持不变。与PF对照相比，EHB奶牛的血尿素氮增加（61％）。总而言之，利用EHB模型表明减少的养分摄入量仅解释了HS期间牛奶产量下降的约50％，并且养分分配后的吸收变化与在气候控制室研究中得出的相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。养分分配的吸收后变化与气候控制室研究得出的结果相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。养分分配的吸收后变化与气候控制室研究得出的结果相似。因此，EHB是研究奶牛环境生理的合理且经济可行的模型。