Managing heat stress this summer

A recent DairyNZ discussion group was presented with data that showed summers in NZ have gotten progressively hotter. Climate change forecasts suggest that summers will continue to become longer, hotter, and drier, and this summer is expected to be no exception.

The National Animal Welfare Advisory Committee is currently discussing improving the regulatory standards for managing heat stress in livestock. Milk companies, such as Fonterra, also now include planning to manage heat stress as part of their well-being requirements for the Co-operative Difference.  

Heat stress is not only an animal welfare concern. It can also increase the risk of lameness, the incidence of disease and impact production and reproduction.

All regions of New Zealand experience summer temperatures likely to cause heat stress. This occurs when cows have more heat than they can get rid of, leading to discomfort and reduced production. Cows begin to experience heat stress at much lower temperatures than humans and prefer temperatures between 4°C - 20°C. Cows generate enormous amounts of heat from digesting food and producing milk. Humidity, solar radiation, and low air movement also contribute to an increased risk of heat stress.

Signs cows are heat stressed:

• Cows breathing faster- check breathing rate
• Cows standing more, but not grazing
• Increased water intake and hanging around water troughs
• Walking slower to and from the shed
• Drop in production (less milk in the vat)
• Drooling, panting, irritability and in some cases sub-clinical rumen acidosis

Considerations for minimising heat stress:

• Ensure adequate shade, strategically utilise shadier paddocks in summer
• Ensure sufficient clean drinking water
• Reduce walking distance and speed
• Adjust milking times or consider OAD
• Assess feed types and timing
• Implement active cooling in the yard with sprinklers and fans and ensure adequate space.
   

Call your local FVS veterinarian to discuss developing heat mitigation strategies for your farm.

Dr Jordan McGimpsey, Farm Vet at Taupiri