Cairbre, later re-christened Leo and the first MGM lion to roar on the silver screen. The problem is, there were at least 5 MGM lions, all of whom were rechristened Leo. The most likely candidate is this one, photographed being filmed in the early 1930s. Hear him roar (or gently growl) in the MGM video.
Cairbre is recorded in the RDS records as having sired 24 cubs, before being put down in 1944 (some say, for attacking a cameraman).
Dublin Zoo was approached again in 1950 to supply 15 lions to kill Christians in the Easter perennial Quo Vadis (1951), starring Robert Taylor and Deborah Kerr. It refused.