Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA.
Department of Dairy Science, Virginia Tech, Blacksburg, VA.
J Anim Sci. 2018 Apr 14;96(4):1375-1387. doi: 10.1093/jas/sky057.
Heat stress (HS) and immune challenges negatively impact nutrient allocation and metabolism in swine, especially due to elevated heat load. In order to assess the effects of HS during Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection on metabolism, 9-wk old crossbred barrows were individually housed, fed ad libitum, divided into four treatments: thermo-neutral (TN), thermo-neutral PRRSV infected (TP), HS, and HS PRRSV infected (HP), and subjected to two experimental phases. Phase 1 occurred in TN conditions (22 °C) where half the animals were infected with PRRS virus (n = 12), while the other half (n = 11) remained uninfected. Phase 2 began, after 10 d with half of the uninfected (n = 6) and infected groups (n = 6) transported to heated rooms (35 °C) for 3 d of continuous heat, while the rest remained in TN conditions. Blood samples were collected prior to each phase and at trial completion before sacrifice. PPRS viral load indicated only infected animals were infected. Individual rectal temperature (Tr), respiration rates (RR), and feed intakes (FI) were determined daily. Pigs exposed to either challenge had an increased Tr, (P < 0.0001) whereas RR increased (P < 0.0001) with HS, compared to TN. ADG and BW decreased with challenges compared to TN, with the greatest loss to HP pigs. Markers of muscle degradation such as creatine kinase, creatinine, and urea nitrogen were elevated during challenges. Blood glucose levels tended to decrease in HS pigs. HS tended to decrease white blood cell (WBC) and lymphocytes and increase monocytes and eosinophils during HS. However, neutrophils were significantly increased (P < 0.01) during HP. Metabolic flexibility tended to decrease in PRRS infected pigs as well as HS pigs. Fatty acid oxidation measured by CO2 production decreased in HP pigs. Taken together, these data demonstrate the additive effects of the HP challenge compared to either PRRSV or HS alone.
热应激（HS）和免疫挑战会对猪的营养分配和代谢产生负面影响，尤其是由于热负荷增加。为了评估猪繁殖与呼吸综合征病毒（PRRSV）感染期间 HS 对代谢的影响，将 9 周龄杂交公猪单独饲养，自由采食，分为四个处理组：常温（TN）、常温 PRRSV 感染（TP）、HS 和 HS PRRSV 感染（HP），并进行两个实验阶段。第一阶段在 TN 条件（22°C）下进行，其中一半动物感染 PRRS 病毒（n = 12），另一半（n = 11）保持未感染。第二阶段开始时，未感染组的一半（n = 6）和感染组的一半（n = 6）在 10 天后被运送到加热室（35°C）进行 3 天的连续加热，而其余的仍留在 TN 条件下。在每个阶段之前和试验结束前处死前采集血液样本。PPRS 病毒载量表明只有感染动物被感染。每天测定个体直肠温度（Tr）、呼吸频率（RR）和采食量（FI）。暴露于任何一种挑战的猪的 Tr 均升高（P < 0.0001），而 RR 随着 HS 的增加而升高（P < 0.0001），与 TN 相比。与 TN 相比，所有挑战都会导致 ADG 和 BW 下降，而 HP 猪的损失最大。肌肉降解标志物如肌酸激酶、肌酐和尿素氮在挑战期间升高。HS 猪的血糖水平有下降趋势。HS 猪在 HS 期间白细胞（WBC）和淋巴细胞减少，单核细胞和嗜酸性粒细胞增加，但中性粒细胞显著增加（P < 0.01）。感染 PRRS 的猪和 HS 猪的代谢灵活性也有下降趋势。通过 CO2 产生测量的脂肪酸氧化在 HP 猪中减少。综上所述，这些数据表明 HP 挑战与 PRRSV 或 HS 单独相比具有累加效应。
