Final answer:
Breeding for dairy heifers should be based on their physical development, typically around 65% of their mature weight, which is usually reached between 13 to 15 months of age, rather than age alone.
Step-by-step explanation:
The question of when breeding should begin for dairy heifers is primarily related to their biological and physical development. While the statement suggests beginning breeding at 11 months, in practice, breeding timing for dairy heifers is typically based on the animal's size and maturity rather than strictly by age. Most dairy heifers are bred when they reach approximately 65% of their mature weight, which generally occurs between 13 to 15 months of age. This approach to breeding helps ensure that the heifers are sufficiently developed to carry and give birth to healthy offspring without compromising their health and growth.
It's worth noting that other species have different mating habits and gestation periods, such as goats, which often reproduce toward the end of their first year, and sheep, whose estrus cycle is influenced by the length of the day.