What is the most likely age range for puberty in a Holstein heifer expected to calve at 24 months?

In Holstein heifers, puberty typically occurs between 9 to 11 months of age. This is an important developmental stage when the heifer's body matures enough to begin estrous cycles, which are essential for breeding and eventual calving. If a heifer is expected to calve at 24 months, reaching puberty at this age range allows adequate time for her to be bred and to develop further before her first calf.

This age range aligns well with industry standards, as heifers are generally bred after reaching puberty, which is essential for reproductive efficiency in dairy operations. The timing also considers the physical maturity necessary for successful calving, as heifers that calve too early may be at risk for health issues.

The other age ranges do not align with the expected onset of puberty in Holstein heifers. Younger ranges, such as 6-8 months, are typically too early, as heifers are usually not physically mature enough for breeding or reproduction at that stage. Similarly, ranges above 11 months can be too late for optimal breeding timing in relation to the desired calving age of 24 months.