England enjoyed a mini heatwave over the weekend. However temperatures have since dropped and rain is now forecast. The image below shows the situation over the past few days in the ‘Highs’ shed at our monitor farm in Wiltshire. On Friday and Saturday temperatures peaked at 25’C, on Sunday they hit 26’C in the shade. Outside in the sunshine it was hotter with the Black Globe temperature peaking at a very uncomfortable 32’C on Friday and on Sunday. The long term heat stress index (THI) exceeded 62 on Thursday afternoon and climbed to a maximum of 66 on Sunday. Our models predict a milk loss of around 1 l/cow/day. The cows were saved by the fall in temperature overnight to 13-14’C which allowed them to shed the heat-load they had built up during the day. As nights get warmer they will not be able to shed their heat-load and heat stress problems will start to accumulate. As of 11:30am Monday morning temperatures in the shed have dropped to 17’C and the 24hr THI score is starting to fall.
