Bart and Lisa watch Saturday morning cartoons, starting with "Transclown-O-Morphs". The show's main character is quickly placed in a life-threatening situation and pleads with the viewers to help him survive by purchasing the new Transclown-O-Morphs cereal. Annoyed by the alleged commercial messages placed in every TV show the kids watch, Marge chooses to get them away from the TV by having Lisa make Banana Bread and Bart go to Shelbyville with Homer to have the beanbag chairs "rebeaned". While Bart and Homer drive to Shelbyville, they see Martin driving a combine harvester. Bart asks why someone like Martin would be driving a tractor, and Martin tells Bart that he has joined 4-H. Lured by the prospect of operating heavy machinery, Bart joins as well and quickly masters driving a tractor. Later, the 4-H volunteer introduces the members to a competition. Taking them to the calf pen, he informs them that they will each pick a calf and raise it over the summer, at the end of which the cattle will be judged at the county fair.
Bart is stuck with the runt of the litter, and is unable to trade it away. He soon meets Mary, and she encourages Bart not to give up in the competition. Bart agrees, and they rename the young bull Lou (previously Lulubelle). Throughout the next several weeks, Bart takes good care of Lou and helps the calf become stronger, while also bonding with Lou and growing to love him. When the day of the competition arrives, Lou has matured into a large bull and is awarded the blue ribbon. Bart is ecstatic until he is told by Lisa that the next step is to send Lou to a slaughterhouse.
Bart tries to convince Marge and Homer to buy the bull, but knowing by experiencehow expensive it isto care for a large animal, they refuse. That night, Bart hears mooing as he lies in bed and believes it to be a hallucination caused by his inability to help Lou. He starts yelling in fear, and Lisa arrives and says it is simply his subconscious telling him to stop eating meat. However, the mooing is suddenly replaced by clucking noises, and Bart discovers that it was only a CD of Tress MacNeille's "Anguished Animals III," placed by Lisa, in an attempt to turn him vegetarian. Nevertheless, Bart, Lisa, and her friends, "Compost" and "Solar Panel", go to the slaughterhouse after hours, determined to save Lou. They discover that Lou, who has been fed growth hormones, is now much bigger, so they use a forklift to pick Lou up and carry him away (although not without some trial and error). Hurrying from the slaughterhouse, they agree the only safe place they can take him is to Mary's home, which is on a farm. The next morning, they are surprised to discover that Mary is the daughter of Cletus Spuckler.
Bart gives the cow to Mary, and Mary agrees to take it. Cletus then calls for Brandine to come to the door. When Brandine learns that Bart offered Mary the cow, she informs them that the giving of a cow constitutes a formal proposal of arranged marriage. Against the wishes of both Bart and Mary, Cletus and Brandine plan the wedding for the next day; Lisa convinces Bart to go along with it so the pair can figure out a way to save Lou, correctly suspecting that Cletus will not keep the bull if Bart refuses. Upon learning what has happened, Homer and Marge are surprised, and Marge devises a scheme to prevent it, but she also agrees to save Lou, realizing how Bart rarely cares about anyone or anything. The next day, Marge arrives to prevent the wedding, prompting Cletus to send Lou to the slaughterhouse. However, the "Lou" Cletus sent was actually Homer in disguise, while the real Lou is being transferred to India to be treated like a god. They save Homer from the slaughterhouse after a close call, after which Homer vows to cut back on his meat eating, and Bart reflects with pride that he can finally say that, "I had a cow, man."