Plastic Animals
Miniature plastic farm animals, such as pigs, cows, chickens and sheep, can be purchased from many discount stores. You can give one to each child who wins a round, or you can give each child one token for every round they win and require them to cash in three tokens for one plastic toy. You can make the tokens something edible, such as animal crackers, and allow the children to eat their tokens when they cash them in.
Stickers
Purchase one small sticker album for each child who will be playing, along with several packages of farm-themed stickers. In addition to farm animals, look for stickers with farm equipment (such as a tractor and pitchfork), barns, farmhouses, scarecrows, and vegetables. Before you start playing the game, give each child an empty sticker album; each time a child wins a round he gets a sticker (or two) to add to his album.
Fake Tattoos
Children love playing with fake tattoos. If you can find some that come in a farm theme, they will make inexpensive prizes that the children will love.
Play-Doh Molds
Another inexpensive option that will please the children is Play-Doh molds shaped like farm animals. Check your local dollar store, as many carry these molds. At the end of the game you can give each child one container of Play-Doh.
Coloring Book
A final idea is a farm-themed coloring book. Depending on how many games you are playing, it may not be practical to give each child a coloring book every time they win, so you may want to incorporate this gift with the token method described in Section 1. As an alternative to edible tokens, you can give each child who wins a round a different color crayon, and give each child a coloring book at the end of the game.