Portion Sizes
Rats need a supply of fresh commercial pellets (called laboratory mix or blocks) available in their cage at all times.

They should also get a small amount (one or two tablespoons each) per day of fruit, vegetables and whole grain bread. These foods make the best treats. You can also give your rat ½ ounce of grain or hamster seed mix as a treat each day.
 
Unlimited fresh water must be available at all times in the rat’s enclosure.

Storage Tips
Store your rat’s commercial diet in a secure container in an area of the house that is cool and dry. Don’t buy more than one or two months’ worth of food at a time because the food loses its nutritional value when stored for too long.

Wash your rat’s food and water bowls daily, being sure to throw away fresh food that hasn’t been eaten after a few hours.