DairyTalk 324: When Heat Stress Exposes Genetic Weakness: Why Extreme Holstein Index Bulls Fail in Arizona - by Helmut Demmelhuber

DairyTalk by Helmut Demmelhuber · Mar 14, 2026 · 21m

This podcast episode is based on a technical article examining the limits of conventional Holstein breeding strategies under extreme climatic conditions. It analyzes a dairy operation in Arizona where bulls with very high indexes for milk production and type perform poorly under heat stress, particularly in terms of fertility and hoof health. A comparison of winter and summer data indicates economic losses of up to $360 per cow, largely driven by declining reproductive performance. In response, the herd’s breeding strategy has shifted toward sires with positive daughter pregnancy rates, more…