Lou is Bart's cow that he becomes very friendly with. Bart befriends him after joining the 4-H club, and trains him so that he wins a blue ribbon at the county fair. After that, Lou is sent to a feed lot for slaughter, but Bart saves him and gives him to Mary Spuckler. In the end, he is saved and sent to India.
When Bart first gets Lou, he was a runt. He was weedy and smaller than the other cows. Bart even offered to trade for Ralph's horse (wooden poles). With all of the love, care and feeding Bart gives him, he becomes stronger even than Nelson's cow.
 Winner of the Blue Ribbon
When he won the blue ribbon, which was first place, Bart found out that Lou was going to be slaughtered. Bart then asked why not slaughter the other losing cows. He then finds out that that Lou is the strongest so he goes first.
 Break Out
When Lou is trapped, ready to be slaughtered, Bart, along with some of Lisa's friends, breaks Lou out, carrying him on a forklift truck, this due to the extra hormones fed to him making him twice his original size. It is then arranged by Apu that Lou will go to India where he will be treated well (better than humans), like all cows there.
- His name Lou comes from shortening Loser, because he was a runt, and the weakest cow out of the stock.