According to the U.S. Environmental Protection Agency, the average gestation period for cows is nine months. Pregnancy in cows lasts 280 days, on average; however, cows can give birth up to 290 days after conception, according to Merck Animal Health.
Generally, the average gestation period for a cow depends on the cow's breed. Manzano Angus Ranches explains that different breeds give birth at different times. For example, Jersey cows give birth at around 279 days after conception while Brahman cows tend to give birth closer to 292 days after conception. Angus cows have a gestation period of around 281 days.