An agricultural expert is warning about the potentially fatal impact of heat stress on livestock, after the Met Office issued its first ever extreme heat warning.

The amber warning was imposed on July 19 and covers large parts of Wales, all of south-west England and parts of southern and central England .

The warning came after all four UK nations recorded the hottest day of the year over the weekend.

Rob Matthews, of rural insurance broker Lycetts, urged farms – particularly mixed farms – to not overlook the effect of rising temperatures on livestock and to take precautionary measures against heat stress.

He said: "Farming is a weather dependent industry, acutely sensitive to temperature extremes, so the summer can be an extremely worrying and testing time of year for farmers, particularly as the weather increasingly oscillates between heavy rainfall and soaring temperatures due to climate change.

"Harvest often takes precedence in these critical months, with time and effort concentrated on maximising yields.

"Of course, the wellbeing of the livestock is also top priority for farmers, but it takes just a few extra degrees, over a relatively short period of time, for animals to suffer the effects of heat stress – it can happen quickly and without much warning.

"Unfortunately, many animals do not have the ability to dissipate enough heat to maintain homeothermy, so even seemingly subtle increases in air temperature can be very harmful and can lead to death.

"An increase in body temperature can also impact on milk productivity in dairy cows, and cause beef cattle to lose condition.

"Farmers care deeply about the wellbeing of their animals and losing animals in this way can be very distressing.

"Farmers can take measures to suit different types of livestock but generally speaking, farmers should monitor heat levels, take measures to keep animals cool when temperatures start to rise, and look out for tell-tale signs, such lethargy, open-mouth panting, reduced food intake and agitation," added Rob.

"Don't forget about working dogs during extreme heat. Avoid working them during the peak of the day and keep them in well ventilated shade with regular access to water. A shallow paddling pool is a fast way for a dog to cool down their body temperature.

"Farmers should also remember that they are not immune to heat stress themselves. Remember to seek shade, particularly at the hottest times of the day, drink plenty of water, and take regular rest periods."