Method for raising poultry

The present invention addresses the problem of providing a method for raising poultry that is effective in improving the weight gain of poultry such as chickens, a method for increasing the muscle mass of poultry, and a method for reducing the expression level of myostatin and/or myogenin in neonatal chicks. In the present invention, feed that includes oxidized glutathione is fed to poultry for a period from hatching to 24 to 168 hours after hatching, which efficiently increases the muscle mass of grown chickens and thus enables efficient production of poultry. The present invention also provides a starter feed composition for poultry that includes oxidized glutathione.