Honestly, corn snakes dont get big enough to really need anything other than mice. The appropriate sized mouse would also have better nutrition (because better developed bones) than the appropriate sized rat. I would just stick to mice and not stress him with rats.
Follow Mark Amey's step by step guide to looking after your pet. Corn snakes are placid, non-poisonous snakes and are good pets for all ages, so follow Video...
Hairless Mice. Rats.Corn snakes are fan favorites among reptile enthusiasts. When looking to own a corn snake, pet lovers should know that they are considered to be very docile plus, the corn snake treats owners to an endless combination of colors and patterns they can enjoy.

Like all other snakes, they are strictly carnivorous; meaning they only eat meat. There are some other species of snakes that eat only birds eggs; but none eat vegetables at all. Corn Snakes prefer small rodents like mice and rats.
BEDDING Most corn snake breeders and keepers use Aspen bedding, as it is soft and absorbent. Reptile carpet is also an option, but the snakes tend to hide under it.Corn snakes thrive on live or frozen/thawed mice. Choose the size of the rodent depending on the size of the snake.
:max_bytes(150000):strip_icc()/the-difference-between-rats-and-mice-2656563-d1cc14057c2c4642896a94899a287a3c.png)
This particular example perfectly highlights why Rat Vs Mice For Corn Snakes is so captivating.
Food Corn Snakes eat mice and rats so the size of the prey is dependent upon the girth of the snake.The bottom line is a thawed prey mouse or rat will never bite or chew on your snake in defense. We have seen nasty rodent bites inflicted on snakes when fed live rodents.
While mice and rats are the gold standard, corn snakes can also safely consume other prey animals like appropriately sized quail and chicks. Raw meat can be used in the short-term in emergencies, but should not be used for a long-term feeding plan.