Methods are disclosed for forming bone and/or cartilage in an avian subject. The methods include administering to the avian subject a therapeutically effective amount of a composition comprising avian mesenchymal stem cells and a hydrogel that supports the differentiation of the avian mesenchymal stem cells into cells of an osteogenic and/or condrogenic lineage. In some embodiments, methods are disclosed for repairing a bone defect and preventing infection, such as that associated bone fracture, in an avian subject. The methods include administering locally to the bone defect a composition comprising a therapeutically effective amount of avian mesenchymal stem cells and a hydrogel, such as a methacrylated gelatin hydrogel.