High doses of cobalt inhibited hair follicle development in Rex Rabbits

An experiment was conducted to investigate the effect of cobalt supplementation on hair follicle development in rabbits. Rex rabbits (30-d-old, n=180) were divided randomly into five equal treatment groups: rabbits fed a basal diet (control, measured cobalt content of 0.27 mg/kg) or rabbits fed a basal diet with an additional 0.1, 0.4, 1.6 or 6.4 mg/kg cobalt (in the form of cobalt sulfate) supplementation (measured cobalt contents of 0.35, 0.60, 1.83 and 6.62 mg/kg, respectively). Treatment with 6.4 mg/kg cobalt significantly decreased hair follicle density ( P 0.05). The addition of dietary cobalt at the highest level examined (6.4 mg/kg) significantly increased the gene expression of bone morphogenetic protein (BMP) 2 and BMP4 in skin tissue ( P 0.05). Compared with their levels in the control group, dietary cobalt treatment significantly suppressed the protein levels of p-mechanistic target of rapamycin (mTOR) and p-ribosomal protein S6 protein kinase ( P 0.05). In conclusion, cobalt at the highest concentration examined inhibited hair follicle development, which may have involved the mTOR-BMP signalling pathway.