Q:We have a 6-year-old Quarter Horse mare and a 21-year-old Paint mare, both in foal to the same Quarter Horse stud. Both were five months along in mid-November (they were bred one week apart). The 6-year-old gained 31 pounds in a six-week period, and the 21-year-old gained 15 pounds in the same time period. Both mares have been ultrasounded and no problems were noted. We have not changed their diets. I was wondering if the weight gain is normal.

—via email

A: Differences of weight gain at the levels described are not significant. First, the fetus attains two-thirds of its size in the last third of gestation. Second, the weight of adult horses can easily fluctuate this much just from roughage and water intake. Don’t worry about it!