Department of Animal Science


Date of this Version

December 1997


Published for Proceedings, The Range Beef Cow Symposium XV December 9, 10 and 11, 1997, Rapid City, South Dakota.


Unlike the dairy breeder or feedlot operator, the beef breeder derives their entire income from calves born into the herd, making fertility unquestionably the most important trait to be considered in a breeding program. Economically, reproductive merit is 5 times more important to the cow-calf producer than growth performance and 10 times more important than product quality (e.g. carcass quality)20, at least until value based marketing becomes a reality. These figures refer to the relative importance of these traits for the beef herd in total and are further magnified when discussing the bull component alone as a result of the male to female ratio at breeding. This is adequate justification to place much greater emphasis on the fertility of the beef bull.

Little selection pressure has been placed on the fertility of the world's beef bull population and as a result, variation in the reproductive potential of beef bulls is vast. Multiple sire breeding, used routinely by commercial breeders, has made it difficult to identify sub-fertile sires. Many breeders, whether purebred or commercial, have little, or no information on the reproductive status of their bulls, particularly their yearlings. Estimates of the proportion of unselected beef bulls in North America that are deficient reproductively range from 20 to 40%. Many more are barely adequate. Few breeders have bull batteries capable of impregnating all females under moderate to heavy breeding pressure in a 45-day breeding season. Achieving this is essential if a 365-day calving interval is to be maintained.