Adapting to increased heat stress in dairy systems

Understanding spatial and temporal nature of heat stress and its impact on milk production at farm to regional scale – exploring effective adaptation options

The Murray dairy region produces approximately 1.85 billion litres of milk each year, representing about 20 % of Australia’s total annual milk production. An ongoing production challenge in this region is the management of the impacts of heat stress during spring and summer. An increase in the frequency and severity of extreme temperature events due to climate change may result in additional heat stress and production losses.

We assesses the changing nature of heat stress now, and into the future, using historical data and climate change projections for the region using the temperature humidity index (THI). Projected temperature and relative humidity changes from two global climate models, CSIRO MK3.5 and CCR-MIROC-H, have been used to calculate temperature humidity index values for 2025 and 2050, and summarised as mean occurrence of, and mean length of consecutive high heat stress periods.

The future climate scenarios explored show that by 2025 an additional 12–15 days (compared to 1971 to 2000 baseline data) of moderate to severe heat stress are likely across much of the study region. By 2050, larger increases in severity and occurrence of heat stress are likely (i.e. an additional 31–42 moderate to severe heat stress days compared with baseline data). This increasing trend will have a negative impact on milk production among dairy cattle in the region.

This work provides useful insights on the trends in temperature humidity index in the region. Dairy farmers and the dairy industry could use these results to devise and prioritise adaptation options to deal with projected increases in heat stress frequency and severity.

Contact Uday Nidumolu for more information.