What kid doesn't love farm animals?? Oh...you there in the pink, your kid doesn't? Well...weird...
Have a farm day! Eat only things from a farm (if you stretch enough you could really make anything come from a farm). Talk about what animal lays eggs, what animals make milk, how crops grow etc. Your child may not understand exactly what you're saying but exposure is key.
Go visit a farm. If you don't have a farm in your area chances are you do have a petting zoo. Check out this website for help finding one. http://www.pettingzoofarm.com/ They have a lot of states missing so try google if you can't find one.
Follow the visit up by some quiet story time about farms. Hit the local library if you don't have any.
If your child is old enough make a craft that has to do with a farm animal. Keep it simple like turkey handprints or make a yellow pom pom into a chick.