How long has it been since his neuter?

The appetite of neutered males is not known to decrease. The body’s need for calories does decrease though, and neutered males can easily become farmer if they get the same amount of food that they ate before the neuter (with the exception of hay of course, they don’t get fat from hay and they should always have unlimited hay).

(I know this is not what you’re asking about, but If your girl bun devours her pellets, I’d suggest you scatter her food rather than serve it in a bowl. Greedy buns that eat very fast can choke on pellets, and that’s really dangerous).

bunnies need pellets daily, the amount depends on their weight. my vet has me feed my 5 pound Holland Lop a 1/4 in the morning and a 1/4 cup in the evening. she gets chopped greens and carrots twice a day and unlimited hay. bunnies still want their pellets. try giving him more pellets instead of greens, but not more than you should for his weight. if my bun doesn’t get her pellets on time she bangs her bowl around.

I might be mistaken on the pellets on the type of bunny you have, mine is a Holland Lop and per my vet who is an expert on Holland Lops (she has 2 of her own) anyway here is a copy of the section on pellets from her bunny care guide she gave me when I first got my bunny.

Pellets are the most common way of providing your rabbit with the necessary vitamins and nutrients they need to grow, develop and stay healthy. There are many different types of rabbit pellets on the market, but there is a fine line between what is actually healthy and what is considered junk food for rabbits. Plain, green pellets are the healthiest kind you can buy. The greener, the better. I know the “fiesta mixes” often look yummier and more appetizing, the rabbits honestly don’t care. As long as they get regular treats, fruits and greens (once they are over 6 months, that is), they will happily eat their plain pellets with out complaint. With the mixes, often the rabbit will pick out its favorite bits and not eat the healthy parts. That can lead to fat rabbit which will cause lots of other problems in the long run.

Small Breeds: 1/4 cup – 1/2 cup per day (2-3oz)
Medium Breeds: 3/4 cup – 1 cup per day (3 1/2-4oz)
Large/Giant Breeds: 1 1/2 cup – 2 cups per day (6-8oz)

Pellets ensure the complete range of vitamins and minerals are in the rabbit’s diet, since it’s difficult to emulate a wild rabbit’s varied diet in pet rabbits (i.e. constant foraging of numerous plants throughout the day). Having a variety of vegetables could somewhat provide this (so I’ve heard a few times), though I would find it difficult to keep up.

Appetite decrease is not normal of neutered males. One thought is your male is more “settled” in terms of food security, and he does not feel pressured to scarf down all the food in one go, in fear it will not be there later. Wick does this with his pellets — he used to eat it all right away, but over time he sort of has his initial “burst”, then goes back and forth to it.

Is he eating selectively less hay as well?