Group of Research in Ruminants (G2R), Department of Animal and Food Sciences, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Department of Agri-Food Engineering and Biotechnology, Universitat Politècnica de Catalunya, Barcelona, Spain.
Sci Rep. 2020 Mar 19;10(1):5055. doi: 10.1038/s41598-020-61900-8.
Heat stress and mastitis are major economic issues in dairy production. The objective was to test whether goat's mammary gland immune response to E. coli lipopolysaccharide (LPS) could be conditioned by heat stress (HS). Changes in milk composition and milk metabolomics were evaluated after the administration of LPS in mammary glands of dairy goats under thermal-neutral (TN; n = 4; 15 to 20 °C; 40 to 45% humidity) or HS (n = 4; 35 °C day, 28 °C night; 40% humidity) conditions. Milk metabolomics were evaluated using H nuclear magnetic resonance spectroscopy, and multivariate analyses were carried out. Heat stress reduced feed intake and milk yield by 28 and 21%, respectively. Mammary treatment with LPS resulted in febrile response that was detectable in TN goats, but was masked by elevated body temperature due to heat load in HS goats. Additionally, LPS increased milk protein and decreased milk lactose, with more marked changes in HS goats. The recruitment of somatic cells in milk after LPS treatment was delayed by HS. Milk metabolomics revealed that citrate increased by HS, whereas choline, phosphocholine, N-acetylcarbohydrates, lactate, and ß-hydroxybutyrate could be considered as putative markers of inflammation with different pattern according to the ambient temperature (i.e. TN vs. HS). In conclusion, changes in milk somatic cells and milk metabolomics indicated that heat stress affected the mammary immune response to simulated infection, which could make dairy animals more vulnerable to mastitis.
热应激和乳腺炎是奶牛生产中的主要经济问题。本研究旨在测试山羊乳腺对大肠杆菌脂多糖（LPS）的免疫反应是否可以通过热应激（HS）来调节。在热中性（TN；n = 4；15 至 20°C；40 至 45%湿度）或 HS（n = 4；35°C 白天，28°C 夜晚；40%湿度）条件下，通过乳腺内给予 LPS 来评估奶山羊的奶成分和奶代谢组学变化。使用 H 核磁共振波谱法评估奶代谢组学，并进行多元分析。热应激使采食量和产奶量分别减少了 28%和 21%。LPS 处理引起 TN 山羊发热反应，但由于 HS 山羊的体温升高，这种反应被掩盖。此外，LPS 增加了奶蛋白，降低了奶乳糖，HS 山羊的变化更为明显。HS 会延迟 LPS 处理后奶中体细胞的募集。奶代谢组学表明，HS 增加了柠檬酸，而胆碱、磷酸胆碱、N-乙酰碳水化合物、乳酸和β-羟丁酸可以被认为是炎症的潜在标志物，其模式因环境温度（即 TN 与 HS）而异。总之，奶体细胞和奶代谢组学的变化表明，热应激影响了乳腺对模拟感染的免疫反应，这可能使奶牛动物更容易患乳腺炎。
