The Moos Room™

What is the ideal age at first calving for Holstein heifers? Brad examines a Zoetis study of nearly 130,000 cows from 74 dairy herds. Although heifers calving at 26 months produced slightly more projected first-lactation milk, those calving around 23 months produced more cumulative milk through two lactations, remained in the herd longer, and generated greater modeled net income.

Replacement risk increased substantially as calving age rose, reaching about 35% for heifers calving at 27 months compared with 17% at 21 months. By 27 months, modeled net income was approximately $650 lower than for the 23-month group because the small milk-production advantage did not offset additional rearing costs and earlier removal from the herd.

The findings support targeting 22 to 23 months—but only when heifers are adequately grown. Brad explains why producers should monitor body weight alongside age, evaluate the costly tail of late-calving heifers, and consider cumulative production and survival rather than relying solely on projected 305-day milk.

Questions, comments, scathing rebuttals? -> themoosroom@umn.edu or call 612-624-3610 and leave us a message!

Linkedin -> The Moos Room
Twitter -> @UMNmoosroom and @UMNFarmSafety
Facebook -> @UMNDairy
YouTube -> UMN Beef and Dairy and UMN Farm Safety and Health
Instagram -> @UMNWCROCDairy
Extension Website
AgriAmerica Podcast Directory