The thermal comfort zone for New Zealand dairy cattle is between 4 and 20 degrees celsius and climate change is increasing temperatures but cattle throughout NZ are likely to be experiencing temperatures that cause thermal stress already.
Heat mitigation tools such as effective shade and altered milking frequency and time will continue to be important but genetics can also be used to develop a more heat tolerant herd.
- Jersey genetics have greater thermal tolerance so full Jersey animals or crossbreeds with a high Jersey component tolerate heat better.
- Gene mutations have been identified that support heat tolerance, e.g. the ‘slick’ gene. In hot conditions, cows with the ‘slick’ gene have been shown to have lower body temperatures and higher milk production compared to non-slick cattle. There is also preliminary evidence that ‘slick’ cows can have improved reproductive performance.
- A small number of bulls carrying the ‘slick’ gene are available in New Zealand. While ‘slick’ cows might not be the best choice for regions with cold winters, herds in hot areas and/or on farms where other heat-mitigation tools are difficult to implement may benefit from introduction of genetics which confer greater thermal tolerance.