While GB milk production has been severely impacted by heat stress in cows, the summer of heatwaves has caused a number of secondary impacts, extending beyond milk volumes.
UK milk composition levels have been particularly high over the past 18 months and remained marginally higher as a percentage of milk volume in August 2026 compared to 2025, according to Defra data. This has been the result of better genetics and better nutrition as returns improved. However, those gains slowed during the summer, following strong growth. Additionally, total milk volumes in the UK were down by 3.5%, meaning that actual volumes of butterfat and protein available to the market were lower, by 1.9% and 2.7%, respectively.
With heat stress and drought impacting farms from May through the summer of 2026, we have seen continuation of the lower volumes coming into September, thereby affecting solids output.