Herman, the world's first genetically modified bull, was put down on Friday at the age of 13 as he suffered from arthritis, its owners said.
Herman was born in December 1990 and bio-tech company Pharming Group NV had given him a human gene so that his female offspring could produce the human lactoferrin protein in their milk for medical use.
Herman's birth caused an uproar in the Netherlands and provoked long debate in parliament on the limits of genetic modification. An ethics commission decided in 1992 the bull could live. He had a total of 55 offspring.
The owners, a foundation, said his illness was unrelated to the genetic modification, adding that the age of 13 was old for a bull.