Search

1. This study investigated the pattern of feather follicle morphogenesis and the expression of the Wnt/β-catenin signalling pathway in the skin of yellow-feathered broiler chick embryos during feather development, using haematoxylin and eosin (HE) staining and Western blot assays, respectively. 2. The results showed that the skin displayed protrusions during embryonic days E7-E9, feather buds elongated during E10-E11 with anterior-posterior and proximal-distal asymmetries, and the epidermis invaginated to form the primary feather follicles (Pfs) at E12. At E13, the formation of the feather follicle and the epidermis at the base of the feather bud further invaginated into the dermis. By E15, Pf formation was essentially complete, and secondary feather follicles (Sfs) appeared. It was speculated that Pfs and Sfs developed independently and that Pfs occurred earlier than Sfs. 3. Quantitative measurements of Pf density reached a maximum at E15 and then decreased gradually. Sf density started to increase from E15. 4. Protein expression levels of β-catenin, TCF4, cyclin D1, and c-Myc were significantly increased during E8-E12 (P 0.05) and then decreased from E13 to the day of hatching (DOH) (P 0.05). The result of the β-catenin immunolocalisation signal intensity assay was consistent with the result of the Western blot assay. 5. Collectively, the results indicated that the Wnt/β-catenin signalling pathway is essential for promoting the development of feather follicles, especially during E7-E15.

Avian feathers have robust growth and regeneration capability and serve as a useful model for decoding hair morphogenesis and other developmental studies. However, the molecular signaling involved in regulating the development of feather follicles is unclear. The purpose of this study was to investigate the role of the Wnt/β-catenin pathway in regulating feather morphogenesis in embryonic chicks through in ovo injection of different doses of Dickkopf-1 (DKK1, a specific inhibitor of the target of the Wnt/β-catenin pathway). A total of 120 fertilized embryo eggs were randomly divided into 4 treatments, including a noninjection group (control group) and groups injected with 100 μL of phosphate-buffered saline (PBS)/egg (PBS control group), 100 μL of PBS/egg containing 600-ng DKK1/egg (600-ng DKK1 group), and 100-μL PBS/egg containing 1,200-ng DKK1/egg (1,200-ng DKK1 group). Feathers and skin tissues were sampled on embryonic (E) day 15 and the day of hatching to examine the feather mass, diameter and density of feather follicles, and the protein expression of the Wnt/β-catenin pathway. The results showed that, compared with CON and PBS treatment, the injection of DKK1 into the yolk sac of chick embryos had no significant effect on the hatching rate and embryo weight (P > 0.05), while it significantly decreased the relative mass of feathers in the whole body (P < 0.05). The high dose of DKK1 (1,200-ng DKK1/egg) decreased the relative mass of feathers on the back, chest, belly, neck, wings, head, and legs, which was more obvious than that in the 600-ng DKK1 group, which presented a dose-dependent effect. In addition, DKK1 injection significantly downregulated the protein expression levels of β-catenin, transcription factor 4, Cyclin D1, and c-Myc (P < 0.05). The immunofluorescence result of β-catenin was consistent with the Western blotting assay results. Altogether, these observations suggested that the Wnt/β-catenin signaling pathway is involved in regulating feather follicle development and feather growth during the embryonic development of chicks.

This study was conducted to explore the regulatory role of the target of rapamycin complex 1 (TORC1) signaling pathway in crop milk synthesis in breeding pigeons (Columba livia). Three groups of breeding pigeons in the lactation period (n = 30 pairs/group) were respectively injected with rapamycin (RAPA, a specific inhibitor of the target of rapamycin complex) at doses of 0 (vehicle, control), 0.6, or 1.2 mg/kg body weight (BW)/day via the wing vein for 7 days. The average daily feed intake (ADFI) and BW of the breeding pigeons and the BW of young squabs were respectively recorded throughout the experimental period. The breeding pigeons were sacrificed to collect their crop tissues, crop milk, and serum on the eighth day of the experiment. The results showed that neither 0.6 nor 1.2 mg/kg BW RAPA injection affected BW loss or ADFI in breeding pigeons (P > 0.05), while crop thickness and crop relative weight were significantly decreased (P < 0.05) in the 1.2 mg/kg BW rapamycin-injected group. Simultaneously, RAPA (especially at 1.2 mg/kg BW) decreased the crude protein, αs1-casein, αs2-casein, β-casein, and amino acid contents (Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Ile, Leu, Tyr, Lys, His, Arg, and Pro) of crop milk (P < 0.05) and the concentrations of albumin, total protein, and uric acid in the serum of breeding pigeons (P < 0.05). Additionally, the expression of TORC1 pathway-related proteins (TORC1, S6K1, S6, 4EBP1, and eIF4E) was downregulated in the crop tissues of breeding pigeons by 0.6 or 1.2 mg/kg BW/day RAPA injection (P < 0.05). Accordingly, the average daily gain (ADG) of young squabs declined, and the mortality rate increased significantly (P < 0.05). Together, the results showed that RAPA reduced protein and amino acid levels in the crop milk of breeding pigeons and retarded young squab growth, suggesting a crucial role of TORC1 in crop milk synthesis in breeding pigeons.

The study aimed to investigate the effects of pioglitazone hydrochloride (PGZ) and resveratrol (RES) on yellow-feathered broiler chickens. A total of 500 broiler chickens were randomly divided into four groups and fed a basic diet (control group) or a basic diet supplemented with 15 mg/kg PGZ, 400 mg/kg RES, or 15 mg/kg PGZ plus 400 mg/kg RES for 28 days. Compared with the control group, the PGZ and PGZ plus RES groups presented a significantly higher average daily gain and a decreased feed-to-gain ratio. Increases in the dressing percentage, semi-eviscerated yield, muscle intramuscular fat content, and C18:1n-9c, C18:3n-6, C20:3n-3, and monounsaturated fatty acid (MUFA) percentages were found in the PGZ plus RES group. Moreover, the diet supplemented with RES or PGZ plus RES increased the activities of catalase, glutathione peroxidase, and superoxide dismutase, and decreased the levels of reactive oxygen species of thigh muscle. Additionally, the mRNA abundance of peroxisome proliferator-activated receptor &gamma, coactivator 1&alpha, fatty acid-binding protein 3, nuclear factor erythroid-2-related factor 2, and superoxide dismutase 1 was increased in the PGZ plus RES group. In conclusion, this study suggested that dietary supplementation of PGZ combined with RES improved the growth performance, the muscle intramuscular fat content, and antioxidant ability of yellow-feathered broiler chickens.

This study aimed to investigate the effects of dietary supplementation with dl-methionine (dl-Met) and dl-methionyl-dl-methionine (dl-Met-Met) in breeding pigeons on the carcass characteristics, meat quality and antioxidant activity of squabs. A total of 324 pairs of breeding pigeons were selected and allotted to 9 treatments in a completely randomized design, and the birds were fed dietary treatments for 45 d, including a Met-deficient basal diet (BD, crude protein = 15%, Met = 0.25%) and BD + 0.15%, 0.30%, 0.45%, or 0.60% dl-Met or dl-Met-Met diets. Compared with the diet fed to the BD group, dietary dl-Met or dl-Met-Met supplementation effectively increased the carcass yield, semieviscerated yield, eviscerated yield, breast muscle yield, thigh muscle yield, a* value, catalase activity, total superoxide dismutase activity and glutathione peroxidase activity, but decreased the L* value, malonaldehyde concentration, drip loss and cooking loss of squabs (p &lt, 0.05). The relative bioavailability values of dl-Met-Met relative to those of dl-Met were 467% and 376% based on carcass yield and breast muscle yield, respectively (p &lt, 0.001). Moreover, dl-Met-Met was more effective than dl-Met in decreasing the drip loss and improving the antioxidant activity of the breast and thigh muscles of squabs (p &lt, 0.05). As a source of Met, dl-Met-Met, rather than dl-Met, was more beneficial to squabs.