Key Laboratory of Animal Genetics, Breeding and Reproduction, MARA, National Engineering Laboratory for Animal Breeding, Beijing Engineering Technology Research Center of Raw Milk Quality and Safety Control, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
College of Life Sciences and Bioengineering, Beijing Jiaotong University, Beijing 100044, China.
J Agric Food Chem. 2023 Aug 9;71(31):11902-11920. doi: 10.1021/acs.jafc.3c00043. Epub 2023 Jul 25.
Heat stress (HS) negatively influences cows' welfare and productivity. Therefore, a better understanding of the physiological and molecular mechanisms of HS responses from multiple parities is paramount for the development of effective management and breeding strategies. In comparison with first-parity cows in the spring (Spring-1), first-parity cows in the summer (Summer-1) had a significantly higher rectal temperature (RT), respiration rate (RR), drooling score (DS), and daily activity (DA), while lower ( < 0.05) daily rumination (DR), seven-day average milk yield (7AMY), milk yield on sampling day (MY_S), milk yield on test day (MY_T), and lactose percentage (LP) were observed. When comparing the spring (Spring-2) and summer (Summer-2) of the second-parity cows, significant differences were also found in RT, RR, DS, DA, and DR ( < 0.05), corresponding to similar trends with the first parity while having smaller changes. Moreover, significantly negative impacts on performance traits were only observed on fat percentage (FP) and LP. These results showed that there were different biological responses between first- and second-parity Holstein cows. Further, 18 and 17 metabolites were involved in the seasonal response of first- and second-parity cows, respectively. Nine differential metabolites were shared between the two parities, and pathway analyses suggested that cows had an inhibited tricarboxylic acid cycle, increased utilization of lipolysis, and a dysregulated gut microbiome during the summer. The metabolites identified exclusively for each parity highlighted the differences in microbial response and host amino acid metabolism between two parities in response to HS. Moreover, glucose, ethanol, and citrate were identified as potential biomarkers for distinguishing individuals between Spring-1 and Summer-1. Ethanol and acetone were better predictors for distinguishing individuals between Spring-2 and Summer-2. Taken together, the present study demonstrated the impact of naturally induced HS on physiological parameters, production traits, and the blood metabolome of Holstein cows. There are different biological responses and regulation mechanisms between first- and second-parity Holstein cows.
热应激（HS）会对奶牛的福利和生产力产生负面影响。因此，更好地了解 HS 反应的生理和分子机制对于制定有效的管理和育种策略至关重要。与春季第一胎奶牛（Spring-1）相比，夏季第一胎奶牛（Summer-1）的直肠温度（RT）、呼吸率（RR）、流涎评分（DS）和日活动量（DA）显著升高，而日反刍时间（DR）、七天平均产奶量（7AMY）、采样日产奶量（MY_S）、测试日产奶量（MY_T）和乳糖百分比（LP）显著降低（<0.05）。当比较第二胎奶牛的春季（Spring-2）和夏季（Summer-2）时，RT、RR、DS、DA 和 DR 也存在显著差异（<0.05），与第一胎相似，但变化较小。此外，仅观察到脂肪百分比（FP）和乳糖百分比（LP）对性能性状有显著负面影响。这些结果表明，第一胎和第二胎荷斯坦奶牛之间存在不同的生物学反应。此外，18 种和 17 种代谢物分别参与了第一胎和第二胎奶牛的季节性反应。两个胎次之间有 9 个差异代谢物共享，通路分析表明，在夏季，奶牛的三羧酸循环受到抑制，脂解作用增加，肠道微生物组失调。每个胎次特有的代谢物突出了两个胎次在应对 HS 时微生物反应和宿主氨基酸代谢的差异。此外，还鉴定出葡萄糖、乙醇和柠檬酸可作为区分 Spring-1 和 Summer-1 个体的潜在生物标志物。乙醇和丙酮是区分 Spring-2 和 Summer-2 个体的更好预测因子。综上所述，本研究表明，自然诱导的 HS 对荷斯坦奶牛的生理参数、生产性状和血液代谢组有影响。第一胎和第二胎荷斯坦奶牛之间存在不同的生物学反应和调节机制。
