The present study aimed to comparatively characterize the ruminal epithelial protein expression profiles in lambs fed ewe milk or milk plus starter diet using proteome analysis. Twenty new-born lambs were randomly divided into a group receiving ewe milk (M, n = 10) and a group receiving milk plus starter diet (M + S, n = 10). From 10 d old, M group lambs remained with the ewe and suckled ewe milk without receiving the starter diet. The lambs in the M + S group were separated from the ewe and received starter feed. All lambs were slaughtered at 56 d old. Eight rumen epithelia samples (4 per group) were collected to characterize their protein expression profiles using proteomic technology. Proteome analysis showed that 31 upregulated proteins and 40 downregulated proteins were identified in the rumen epithelium of lambs in response to starter diet supplementation. The results showed that starter feeding regulates a variety of biological processes in the epithelium, especially blood vessel development and extracellular matrix protein expression. Meanwhile, the expression of proteins associated with synthesis and degradation of ketone bodies, butanoate metabolism, and citrate cycle signaling transduction pathway were upregulated in the group with starter diet supplementation, including 3-hydroxy-3-methylglutaryl coenzyme A synthase (HMGCS2, fold change [FC] = 1.93), 3-hydroxybutyrate dehydrogenase 1 (BDH1, FC = 1.91), and isocitrate dehydrogenase 1 (IDH1, FC = 8.12). The metabolic processes associated with ammonia detoxification and antioxidant stress were also affected by starter diet supplementation, with proteins, microsomal glutathione S-transferase 3 (MGST3, FC = 2.37) and IDH1, linked to the biosynthesis of glutamate and glutathione metabolism pathway being upregulated in the group with starter diet supplementation. In addition, starter feeding decreased the expression of Ras-related protein rap-1A (RAP1A, FC = 0.48) enriched in Rap1 signaling pathway, Ras signaling pathway, cyclic adenosine monophosphate (cAMP) signaling pathway, and mitogen-activated protein kinase (MAPK) signaling pathway. In summary, starter feed supplementation changed the expression of proteins related to energy production, ammonia detoxification, antioxidant stress, and signaling pathways related to proliferation and apoptosis, which facilitates the rumen epithelia development in lambs. The results provide new insights into the molecular adaptation of rumen epithelia in response to starter diet supplementation at the protein level in lambs.

本研究旨在使用蛋白质组分析比较表征饲喂母羊奶或牛奶加起子日粮的羔羊的瘤胃上皮蛋白表达谱。20 只新生羔羊被随机分为一组接受羊奶（M，n  = 10）和一组接受牛奶加开胃饲料（M + S，n = 10）。从10日龄开始，M组羔羊与母羊和母乳喂养的母羊奶不接受开食日粮。M+S组的羔羊与母羊分开，接受开食料。所有羔羊均在56日龄时屠宰。收集了 8 个瘤胃上皮样品（每组 4 个）以使用蛋白质组学技术表征它们的蛋白质表达谱。蛋白质组分析表明，在补充开胃饲料的羔羊瘤胃上皮中鉴定出 31 种上调蛋白和 40 种下调蛋白。结果表明，发酵剂喂养调节上皮细胞的多种生物过程，尤其是血管发育和细胞外基质蛋白表达。同时，与酮体合成和降解、丁酸代谢、和柠檬酸循环信号转导通路在添加起始饮食的组中上调，包括 3-羟基-3-甲基戊二酰辅酶 A 合酶（HMGCS2，倍数变化 [FC] = 1.93）、3-羟基丁酸脱氢酶 1（BDH1，FC = 1.91 ) 和异柠檬酸脱氢酶 1 (IDH1, FC = 8.12)。与氨解毒和抗氧化应激相关的代谢过程也受到初始饮食补充的影响，蛋白质、微粒体谷胱甘肽 S-转移酶 3（MGST3，FC = 2.37）和 IDH1，与谷氨酸的生物合成和谷胱甘肽代谢途径在补充起始饮食的组。此外，饲喂降低了富含 Rap1 信号通路、Ras 信号通路、环磷酸腺苷 (cAMP) 信号通路和丝裂原活化蛋白激酶 (MAPK) 信号通路。总之，添加起始饲料改变了与能量产生、氨解毒、抗氧化应激以及与增殖和凋亡相关的信号通路相关的蛋白质的表达，从而促进了羔羊瘤胃上皮的发育。该结果提供了对瘤胃上皮细胞在蛋白质水平上对起始日粮补充的反应的分子适应性的新见解。这有助于羔羊瘤胃上皮的发育。该结果提供了对瘤胃上皮细胞在蛋白质水平上对起始日粮补充的反应的分子适应性的新见解。这有助于羔羊瘤胃上皮的发育。该结果提供了对瘤胃上皮细胞在蛋白质水平上对起始日粮补充的反应的分子适应性的新见解。