Methionine improves feather follicle development in chick embryos by activating Wnt/β-catenin signaling

This study was conducted to explore the regulatory role of methionine (Met) in feather follicle and feather development during the embryonic period of chicks. A total of 280 fertile eggs (40 eggs/group) were injected with 0, 5, 10, 20 mg of L-Met or DL-Met/per egg on embryonic day 9 (E9), and whole-body feather and skin tissues were collected on E15 and the day of hatching (DOH). The whole-body feather weight was determined to describe the feather growth, and the skin samples were subjected to hematoxylin and eosin staining and Western blotting for the evaluation of feather follicle development and the expressions of Wingless/Int (Wnt)/β-catenin signaling pathway proteins, respectively. The results showed that L- or DL-Met did not affect the embryo weight (P > 0.05), but increased the absolute and relative whole-body feather weights. Specifically, 5 and 10 mg of L-Met and 5, 10, and 20 mg of DL-Met significantly increased the absolute feather weight at E15 (P < 0.05), and 10 mg of L-Met and 5 and 10 mg of DL-Met significantly increased the absolute and relative feather weight on the DOH (P < 0.05). Moreover, a main effect analysis suggested that changes in the embryo and feather weights were related to the Met levels (P < 0.05) but not the Met source (P > 0.05). The levels of L- and DL-Met were quadratically correlated with the absolute and relative feather weights of chicks on the DOH (P < 0.05). Correspondingly, all doses of L- and DL-Met significantly increased the diameter and density of feather follicles on the DOH (P < 0.05), as well as the activity of Wnt/β-catenin on E15 and the DOH (P < 0.05). In conclusion, injection of either L- or DL-Met can improve feather follicle development by activating Wnt/β-catenin signaling, and thereby promoting feather growth; furthermore, no difference in feather growth was found between L- and DL-Met treatments. Our findings might provide a nutritional intervention for regulating feather growth in poultry production.