Thanks for using Petco Pet Education Center, formerly Petcoach! If just eating chicken breast then it would be about 10 ounces. This is based on a daily caloric intake of about 465 calories. Keep in mind that it is recommended to give a protein with a carbohydrate such as rice which then would lower the amount of chicken. You can always check the calories in whatever you decide to feed him knowing that it should be about 465 calories. Good luck!