All of these relationships are undesirable. Steeper foot angles and shorter claw length were associated with fewer days open, greater survival to five years of age, and older ages at culling, all desirable results. Deeper heels meant more days open, but increased longevity. To producers, these relationships mean that selection to improve feet will reduce genetic progress for production. On the other hand, unrestricted selection to improve milk yield might cause enough genetic deterioration in foot angle to be a problem, especially since some reproductive functions also suffer with deterioration of foot structure.
Farmers use genetic evaluations based on classification scores rather than research data.
Heritabilities and relationships between some linear type traits from Holstein type classifications and lifetime performance traits are in Table 2. Low scores for rear legs side view indicate straight hocks, high scores indicate sickled hocks, and intermediate values are considered best. The heritability for foot angle is 10 percent using classification data, meaning that progress for foot angle using Holstein linear trait data will be slower than if actual measurements were used. The heritability of legs side view is 16 percent, indicating that some changes could be achieved through sire selection. Genetically, feet and leg traits have little relationship to lifetime profit or herdlife.