The Farming EP is, along with Generations, the most requested EP during this las time.
The reasons are mostly the lack of another fauna in the game besides cats, dogs and fishes. In The Sims 2 but specially in The Sims 3, you can find chickens, deers, cows, horses, wolves and skunks. Another objects and rural related activites also are high demanded by the players, like crafting hobbies (sewing and pottery), composting, lawn mowing, homemade food (cheese, butter), canning (jam, pickles, sauce) more harvestables and building tools like natural ponds.
Also, the possibly of adding medieval and off the grid like activities like forging, archery or wood chopping makes a farming EP in the top of the most requested packs for TS4.
I don't think you will raise animals for later killing thems and eat them in TS4, i think you will raise thems for other propouses like milk, fiber or eggs.