Up to 8 hens are allowed to be kept per residence provided that the hens are confined in a coop that is no less than 25 feet from any habitable structure on a neighboring property. Roosters and all other fowl are prohibited in residential zoning districts
https://www.killeentexas.gov/FAQ.aspx?TID=15
https://www.killeentexas.gov/FAQ.aspx?TID=15