Willlllbbbburrrr, from "Mister Ed". Apparently, Mr Ed himself died in 1970 at age 21, according to how I am interpreting the really poorly written blog post in sfgate (
http://www.sfgate.com/entertainment/the-wrap/article/Alan-Young-Star-of-Mister-Ed-Dies-at-96-7874611.php).
The actor’s equine “Mister Ed” costar, Bamboo Harvester, appeared on the series from 1949 until 1970, when he euthanized after suffering from a number of health ailments. The lovable Palomino was later buried at Snodgrass Farm in Oklahoma.
The series ran from '61 to '66.