Temporal associations between night-time wind chill and milk performance in dairy cows

Cold stress can reduce dairy cow performance, but little is known about whether production responses reflect current weather conditions or cold exposure accumulated over preceding days. We examined this temporal dimension during two naturally occurring cold waves in a commercial Brown Swiss herd in Ukraine. Daily herd-level milk yield, milk fat, milk protein and somatic cell count (SCC) were related to concurrent and 3-, 7-, 10- and 14-day antecedent wind chill temperature (WCT) using general linear models adjusted for calendar day. Mean night-time WCT was the primary exposure metric, with daily minimum WCT used in an independent sensitivity analysis. Milk yield declined progressively across the cold-event sequence and reached its lowest level after the second cold wave, when meteorological conditions had already improved. Its strongest adjusted association occurred with the preceding 10-day WCT exposure (partial η² = 0.174), a pattern independently reproduced using daily minimum WCT (partial η² = 0.207). Milk fat showed an earlier and substantially stronger association, peaking at the 7-day window with both WCT metrics (partial η² = 0.566 and 0.568, respectively). Milk protein was not independently associated with cold exposure, whereas SCC showed a comparatively modest 7-day association. These findings provide preliminary evidence that milk responses to pronounced winter cold may be temporally structured and trait-specific rather than synchronous with current meteorological conditions. Antecedent exposure windows may therefore provide additional information beyond current-day WCT when assessing short-term cold-related responses in dairy herds.