Anhui Provincial Key Laboratory of Livestock and Poultry Product Safety Engineering, Institute of Animal Husbandry and Veterinary Medicine, Anhui Academy of Agricultural Sciences, Hefei, Anhui, China.
College of Animal Science and Technology, Yangzhou University, Yangzhou, China.
PeerJ. 2023 Apr 7;11:e15112. doi: 10.7717/peerj.15112. eCollection 2023.
Heat stress causes infertility in male rabbits in summer. This study was conducted to determine the effects of heat stress on semen quality and seminal plasma metabolites of male rabbits. To achieve these objectives, the temperature and humidity index (THI) was used to determine the stress state of male rabbits during different months, thereby the rabbits were divided into heat stress and no heat stress groups. The quality of the semen and the biochemical indices of seminal plasma were then analyzed. Next the plasma metabolites of rabbits in both groups were evaluated using the ultra-high performance liquid chromatography-mass spectroscopy (UPLC-MS)/MS technique. Our results showed that the THI value of the rabbit housing in May was 20.94 (no heat stress). The THI value of the housing in August was 29.10 (heat stress group, = 10). Compared with the non-heat stress group, the sperm motility, density, and pH in the heat stress group ( = 10) were significantly decreased ( < 0.01); the semen volume decreased significantly ( < 0.05); and the sperm malformation rate increased significantly ( < 0.01). The number of grade A sperm significantly decreased, while the numbers of B and C grade sperm significantly increased ( < 0.01). The total sperm output (TSO), total motile sperm (TMS), and total functional sperm fraction (TFSF) decreased significantly ( < 0.01). Heat stress protein 70 (HSP70) and acid phosphatase (ACP) in the seminal plasma of rabbits in the heat stress group ( = 20) were significantly increased ( < 0.01). Seminal plasma testosterone (T), α-glucosidase (α-Glu), and fructose decreased significantly ( < 0.01). The concentrations of Mg ( < 0.05), Na ( < 0.01), and K ( < 0.01) in metal ions were significantly decreased. These findings indicated that heat stress severely affected the quality of the male rabbit semen. Furthermore, UPLC-MS/MS technology was used to analyze the seminal plasma samples of rabbits in the heat stress group and non-heat stress group ( = 9 for each group). In total, 346 metabolites were identified, with variable importance in project (VIP) > 1.0, fold change (FC) > 1.5 or < 0.667, and < 0.05 as the threshold. A total of 71 differential metabolites were matched, including stearic acid, betaine, arachidonic acid, L-malic acid, and indole. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differential metabolites revealed 51 metabolic pathways, including synthesis and degradation of ketones, serine and threonine metabolism, tryptophan metabolism, and the citric acid cycle. Our study has shown that the sperm motility, sperm pH value, and sperm density of male rabbits decreased significantly under heat stress, and the sperm malformation rate increased significantly. Furthermore, the quality of semen was shown to deteriorate and the energy metabolism pathway was disturbed. These findings provide a theoretical reference for alleviating the adaptive heat stress in male rabbits.
夏季高温会导致公兔不育。本研究旨在确定热应激对雄性兔子精液质量和精液浆代谢物的影响。为此，我们使用温度和湿度指数（THI）来确定不同月份雄性兔子的应激状态，从而将兔子分为热应激组和非热应激组。然后分析精液质量和精液浆生化指标。接下来，使用超高效液相色谱-质谱联用技术（UPLC-MS/MS）评估两组兔子的血浆代谢物。结果表明，5 月份兔舍的 THI 值为 20.94（非热应激），8 月份兔舍的 THI 值为 29.10（热应激组， = 10）。与非热应激组相比，热应激组（ = 10）的精子活力、密度和 pH 值显著降低（ < 0.01）；精液量显著减少（ < 0.05）；精子畸形率显著增加（ < 0.01）。A级精子数量显著减少，B 级和 C 级精子数量显著增加（ < 0.01）。总精子输出量（TSO）、总活动精子（TMS）和总功能精子分数（TFSF）显著减少（ < 0.01）。热应激组（ = 20）的热应激蛋白 70（HSP70）和酸性磷酸酶（ACP）显著增加（ < 0.01）。精液浆睾酮（T）、α-葡萄糖苷酶（α-Glu）和果糖显著减少（ < 0.01）。金属离子中 Mg（ < 0.05）、Na（ < 0.01）和 K（ < 0.01）的浓度显著降低。这些发现表明，热应激严重影响雄性兔精液质量。此外，使用 UPLC-MS/MS 技术分析热应激组和非热应激组（每组 9 只）的兔精液浆样本。总共鉴定出 346 种代谢物，VIP > 1.0、FC > 1.5 或 < 0.667 和 < 0.05 作为阈值。总共匹配到 71 种差异代谢物，包括硬脂酸、甜菜碱、花生四烯酸、L-苹果酸和吲哚。差异代谢物的京都基因与基因组百科全书（KEGG）富集分析显示 51 条代谢途径，包括酮的合成和降解、丝氨酸和苏氨酸代谢、色氨酸代谢和柠檬酸循环。本研究表明，雄性兔子在热应激下精子活力、精子 pH 值和精子密度显著下降，精子畸形率显著升高。此外，精液质量恶化，能量代谢途径受到干扰。这些发现为缓解雄性兔子的适应热应激提供了理论参考。
