How young do calves go in heat?

Calves do not go into heat. Heat is the term used to describe the fertile phase of the estrous cycle in female mammals. Calves are young cattle, and female cattle are called heifers until they have given birth to their first calf. Heifers typically reach puberty and begin cycling between 12 and 18 months of age, but this can vary depending on the breed and individual animal.