Normally, which of the following would experience the most calving problems?

First calf heifers are often the group that experiences the most calving problems due to several factors related to their age, size, and experience. As they are having their first calves, they may not have fully developed pelvic dimensions, which can lead to difficulties during birth. Additionally, being first-time mothers, they lack the experience to cope with the physical demands of calving, which can also contribute to complications.

Mature cows and second calf cows generally have more experience and better-developed bodies to handle the stresses of calving, which leads to fewer complications compared to first calf heifers. Thus, while calving problems can occur in any group, first calf heifers are statistically the most likely to face challenges during this process.