Although overall reproductive performance decreases with increasing parity, high-parity cows vary widely in their reproductive performance; this may be the reason that no significant differences in CFSI were detected among the herd size groups for high-parity cows. Thus, it is important to cull older cows showing signs of low fertility to improve herd reproductive efficiency. Generally, older cows are culled at 10 years of age once their calf is weaned [25]. However, recommendations with respect to culling or retaining nonpregnant females must be based on both biological and economic considerations [5].