A period of warm weather is continuing for much of the west-central Europe this week. In the UK an “extreme heat” warning has been issued by the Met Office for sunday 17 July, and the following two days, for the south east of the country. Whereas this event will pose a risk for human health, livestock health and comfort are going to be impacted too. For dairy cattle, this event is likely going to result in significant heat stress and impact milk production .

High pressure continues to dominate Europe and the UK the coming days, prolonging the warm spell for many and reaching extreme temperatures over 40°C in many sites. This heatwave had already been anticipated at the end of June by long term forecasts. Remarkably, and for the first time in history a model output from the Global Ensemble Forecast System (GEFS) showed the potential of reaching the record maximum temperature of 40 °C for the southern UK.   This would break all records, as the current max temperature record is 38.7°C, set in 2019. More importantly, this would not be a punctual record, but would affect a very large area of the country.

Cow heat stress

The Temperature Humidity Index (THI) is a score which quantifies the combined effects of excessive heat temperature and relative humidity on cow health and can be useful in assessing the actual strain under which cows are placed during heat waves. The THI map for the UK based on the weather forecasted next week indicates that in a large region in the center-south east of the UK, cattle will undergo severe heat stress, with scores between 80 and 90.

The effect of climate change on cow heat stress and production is already evident

Unfortunately, as climate change will make these heat waves more and more frequent, there will likely be repercussions on dairy farm production and animal welfare. These effects can be appreciated by looking at the evolution of THI and its effect on milk production in the last 40 years. The tendency is clearly for an increase in heat stress related milk loss over the last decades. As shown by the figure below, for southern UK whereas 30 years ago cumulated milk loss over the year reached peaks of minus 25-30 liters less per cow on a particularly hot year, in recent years (for example 2020) it reaches extremes of -40 liters per cow. loss(1)


Heat stress solutions

Dairy farm survival to climate change depends on their capacity to ensure animal comfort and put in a place a timely and suitable adaptation strategy during extreme events.

Monitoring tools have been developed to keep an eye on the herd at all times. One of them is Farmlife, an ITK tool for monitoring livestock health and reproduction. Farmlife has  recently been enriched by a new service to forecast heat stress, Heat Adapt. This service is based on gridded weather forecasts used to calculate the THI, and allows stockbreeders to act at the first signs of heat stress to avoid a decrease in milk production and reproduction problems. The dynamic behaviour indicators in Farmlife allow to monitor the effects of the measures taken to mitigate and contrast heat stress.

Finally, the dairy farm can take advantage and implement of the measures taken by farms in similar conditions that are able to maintain higher levels of production to increase its resilience. Heat Adapt is a comprehensive solution that helps stockbreeders to anticipate, mitigate and adapt to heat stress events.