How to Calculate the Generation Interval of Horses

The generation interval is a statistic which identifies how quickly a particular family or line reproduces. The generation interval of horses can be calculated for either a family or for a direct line. A generation interval for a family calculates the average age of one generation of parents at the time when their offspring is born, but it gives no calculation to the intervals of previous generations. Calculating a generation interval for a direct line is more complicated, and focuses on select parents and offspring in the line. The parent's age at the time of the offspring's birth is averaged, which produces the generation interval.

Things You'll Need

  • Ages of the sire and dam of the foal at a foal's birth date
  • Birth years of the first and last members of a line
Show More

Instructions

  1. Calculating the Generation Interval for a Family

    • 1

      Find the age (in years) of each parent at the time of their foal's birth. Round the age to the nearest tenth (if the foal's sire was 15 years and 6 months old at the time, he was 15.5).

    • 2

      Calculate these ages for every foal that the sire and dam have had together and record them. If the sire and dam have had three foals together, then you should have three pairs (one pair for each of the foals) of two ages (one for the sire and one for the dam).

    • 3

      Add all of these ages together and divide them by the number of ages to find their average. (Using the example from Step 2, you would divide the total of all ages by 6, since there are three pairs of ages). The resulting figure is the generation interval for the family.

    Calculating the Generation Interval for a Direct Line

    • 4

      Determine the birth years of the first and last members of the generation line. The last member would be the foal which was most recently born, and the first member would be the sire or dam from which the particular line originates.

    • 5

      Subtract the birth year of the first generation from the birth year of the last generation. Record this figure.

    • 6

      Divide the resulting figure by the number of generations between the first generation and the last generation of the line. The resulting figure is the generation interval for the direct line.