A:   Usually heifers reach puberty between 12 and 15 months of age. This can differ by breed and how they are developed. Brahman breeds are later at reaching puberty than British breeds or Continental breeds. Puberty in beef cattle is a function of weight, followed by age. There are, in some cases, that beef females will cycle at less than a year of age and become pregnant. This is called precocious puberty. These females may be still nursing their dams. This doesn't happen often, but can happen.