I've got two at the moment, one a puppy, and have had the breed before .Diet. The adult bitch eats 2 x 1.2 kilo 'big' tins of Butcher's loaf [NOT the stuff in jelly] every day plus some biscuit. She's ten years old. A dog, being bigger, would eat more.
The pup has to have special food for large breed puppies. You must not feed a wolfhound pup ordinary dog or puppy food, because they grow so fast and so big that they need what only the special food contains.I feed my puppy Pro-Plan Puppy Large Protection Athletic, mixed with a little tinned meat to make it a bit moist. He drinks two or even three litres of goat's milk most days, too (not cow's milk. Cow';s milk is a too rich for a pup).He's now 15 weeks.
The advice on having a pup, given in the Irish Wolfhound Club link above, is very sound. They are quite clumsy when growing,, at least to a year. And it's important to understand that they can reach a lot higher than ordinary dogs yet are still juvenile far older than other breeds. They can chew furniture to quite a height! A bitch isn't fully grown until two years or so and a dog nearly three years.
Temperamentally they are a soft breed, very affectionate. They'd never make guard dogs ! They need far less exercise than you'd think but when they do run they make it really worthwhile.You have to keep an eye on them because if they see a hare you'll need a helicopter!