The Siboney de Cuba is a hybrid breed of cattle optimized for survival in harsh environments. They comprise 5-8 Holstein Friesian and 3-8 Zebu (Bos indicus). As such they are a true hybrid of two species - however they are fertile (although they do not of course breed true). The breed was originally created in the 1970s to improve the milk yields of the hardy but poor yielding zebu by incorporating genes from the more productive but also more frail Holstein.