Here is an easy to accomplish example of monitoring.
5cm increments are drawn on the race, the heifers are measured against it and their withers height recorded.
These heifers are 12 months old. A Holstein heifer should have a withers height of 124cm by this time.
If heifers are not achieving good enough growth rates, and we discover this early enough, feeding can be altered so that service can still be achieved by 13-15 months of age.