Heat Stress During the Transition Period is Associated with Impaired Production, Reproduction, and Survival in Dairy Cows

The objectives of this retrospective cohort study were to determine the association heat stress exposure during transition period with production, health, reproduction, and survival first 90 days postpartum in dairy cows. A total 5,722 Holstein cows (2,324 heifers 3,397 cows) categorized into environmental condition (EC) groups based on average temperature humidity index (THI) as thermoneutral (TN) or (HS) pre (Pre) early (Post) periods TN-TN, TN-HS, HS-TN, HS-HS. In heifers, HS Pre, Post, Pre Post was associated a 3.7-lb/d reduction milk yield compared TN-TN. Postpartum increases 4.4-percentage points incidence retained placenta, 18.1-percentage metritis, 2.0-percentage mastitis, 5.3-percentage pregnancy at AI, an increase 4.5-percentage loss TN. cows, 5.3-lb/d when increased placenta 5.8-percentage within whereas no difference found TN Metritis by 6.3-percentage For per reduced 10.6-percentage Removal from herd exposed Post. These data suggest that is performance losses greater extent than prepartum are vulnerable period.