BIG HORN BISON CONSERVATION HERD
Mature cows weigh between 1,000 and 1,500 pounds, reaching peak physical maturity at 8 to 10 years of age. They can live to be 30 years old or more. With good management, cows can reproduce every year and can begin breeding at two years of age. The normal gestation period is 280 to 285 days. The breeding season begins in August and continues into October, while the calving season begins in May and continues into July. Bulls weigh about 2,000 pounds at maturity and can be used for breeding at two years of age. One bull can breed 10 to 15 cows.
Some producers are trying artificial insemination, but natural breeding methods are safer because of the bison’s unpredictable temperament and the scarcity of bison semen. To prevent inbreeding and improve the herd, new young bulls should be brought into the herd every two or three years. Do not keep any one bull in the same herd for longer than three years. However, if you have a superior bull (a high-producing, dominant bull), it may be difficult to rotate new bulls into the herd. You can separate the calves after weaning and sell the calves at slaughter weight. This will allow you to keep a superior bull longer than two to three years. The goal of the producer should be to improve the performance of the herd by breeding and selecting bigger animals that gain weight faster. The following practices are recommended for a herd breeding program:
Keep accurate health and reproduction records.
Cull cows that are difficult to breed and animals that are slow to recover from sickness or injury or that gain weight slowly.
Cull all but the best bulls, and bring new young bulls into the herd for breeding on a regular basis.