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The objective of our study was to assess the effect of rumen-protected niacin supplementation on the transcriptome of liver tissue in growing Angus × Simmental steers and heifers through RNA-seq analysis. Consequently, we wanted to assess the known role of niacin in the physiological processes of vasodilation, detoxification, and immune function in beef hepatic tissue. Normal weaned calves (~8 months old) were provided either a control diet or a diet supplemented with rumen-protected niacin (6 g/hd/d) for a 30-day period, followed by a liver biopsy. We observed a significant list of changes at the transcriptome level due to rumen-protected niacin supplementation. Several metabolic pathways revealed potential positive effects to the animal’s liver metabolism due to administration of rumen-protected niacin; for example, a decrease in lipolysis, apoptosis, inflammatory responses, atherosclerosis, oxidative stress, fibrosis, and vasodilation-related pathways. Therefore, results from our study showed that the liver transcriptional machinery switched several metabolic pathways to a condition that could potentially benefit the health status of animals supplemented with rumen-protected niacin. In conclusion, based on the results of our study, we can suggest the utilization of rumen-protected niacin supplementation as a nutritional strategy could improve the health status of growing beef cattle in different beef production stages, such as backgrounding operations or new arrivals to a feedlot.

本研究旨在通过RNA测序（RNA-seq）分析，探究过瘤胃烟酸（rumen-protected niacin）补充对生长阶段安格斯×西门塔尔阉牛与青年母牛肝脏组织转录组的影响。同时，本研究亦旨在明确烟酸在肉牛肝脏组织的血管舒张、解毒及免疫功能等生理过程中的已知调控作用。本研究选取约8月龄的断奶犊牛，随机分为两组，分别饲喂基础对照日粮与添加6 g/头/天过瘤胃烟酸的试验日粮，干预周期为30天，随后采集肝脏活检样本。研究结果显示，补充过瘤胃烟酸可显著改变肝脏组织的转录组表达谱。多条代谢通路因过瘤胃烟酸的施用呈现出对肉牛肝脏代谢的潜在积极效应，具体表现为脂解作用、细胞凋亡、炎症反应、动脉粥样硬化、氧化应激、纤维化及血管舒张相关通路的表达水平下调。综上，本研究表明，过瘤胃烟酸补充可使肝脏转录调控系统重塑多条代谢通路，有望提升受试肉牛的健康水平。综上所述，基于本研究结果，我们建议将过瘤胃烟酸补充作为一项营养调控策略，用于改善不同肉牛生产阶段的牲畜健康状况，例如育肥前期饲养环节或新进育肥场的肉牛。