Cows PRE-1900 Treatment for smallpox — one of the world’s most dreaded plagues, estimated to have caused 2,000,000 deaths as recently as 1967; declared eradicated in 1977.

Horses 1940s Prevention of diphtheria — an acute contagious disease marked by formation of membranes in the throat and other air passages, causing difficulty in breathing, high fever, weakness, and often death.

Cows, Pigs 1980s Organ transplant techniques — surgical and medical advances such as anti-rejection drugs to enable heart, liver, lung, and other transplants to succeed.