AbstractIn this experiment, in order to study the formation mechanism of the lamb fur of Tan sheep, skin samples were collected from Tan sheep at the newborn and er-mao stages. Then, the phosphorylated proteomes of the skin samples of Tan sheep at the two different stages were compared and analyzed using a TMT labeled quantitative phosphorylation proteomic technique. A total of 2806 phosphorylated proteins were identified, including 8184 phosphorylation sites. The results of this study’s quantitative analysis showed that when compared with the skin samples at the er-mao stage, the phosphorylation levels of 171 sites had been upregulated in the skin samples at newborn stage. Meanwhile, 125 sites had been downregulated at the same stage. As shown by the results of the functional enrichment analysis of the differentially phosphorylated proteins, they had been mainly enriched in the cysteine and methionine metabolism. In addition, the phosphorylation levels of KAP4.7 and KAP13.1 had also varied during the different skin stages. These results indicated that the cysteine metabolism pathways, as well as the phosphorylation modifications of the keratin associated proteins in the skin, played important roles in the formation of the er-mao stage fur of the Tan sheep. Therefore, the findings of this study provided a new angle for interpreting the formation mechanism of er-mao stage fur properties.