A cow carries a calf for nine months, according to the Environmental Protection Agency. Females sexually mature at 15 months and are bred to optimally deliver their first calf at two years of age. After a brief two- to three-month interval, they are bred again.
The ideal gestation for each heifer is one calf every year. Gestation periods vary depending on breed, however, as reported in a 2013 issue of the Angus Beef Bulletin. Breeders document gestation lengths according to whether the breeding is natural or through artificial insemination, which is why a nine-month average is considered the median gestation period for all cattle. For example, Jersey cow gestation takes an average of 279 days, and Brahmans take up to 292 days. Among all breeds, the gestation period varies by 12 days on either side of the average.