Is your herd suffering from heat stress?...

When we hear ‘Heat Stress’, it can often be thought of as something that occurs when there is extreme heat and sunshine. However, the reality is that cows are extremely sensitive to the complex mixture of relative humidity and fluctuating air temperature which all combine to increase a cow’s core body temperature, exceeding its capacity for heat dissipation causing heat stress.

In the UK, fluctuating temperatures occur often during the warmer months. In 2019 between May and August temperatures fluctuated daily by up to 12C from one day to the next.

Even during these fluctuating temperatures, weather measurements show humidity doesn’t often fall below 60% which is seen as the ‘trigger level’ on Temperature-Humidity Index (THI) scales meaning we are almost constantly at the trigger level throughout the summer months even combines with our mediocre temperatures!

The UK often experiences heat stress conditions from June to August, which negatively impacts fertility and performance of herds. (Figure 1) From the graph below you can see that fertility was negatively affected from the very modest THI level of 57. This helps explain the impacts we typically see on fertility and production throughout the summer months.

Fluctuating temperatures cause cows to alter their normal daily routine, with changes to their behaviour which can negatively impact on their production and welfare.

• Drop in appetite

• Lower feed intake

• Panting and drooling

• Choosing cubicles at each end of the shed

• Huddling around fans

• Eating and drinking from troughs that are out of the sun

• Standing still, not laying down

  
  

Heat-stressed animals reduce their feed intake. This is presumably a survival strategy, especially in ruminants, as digesting and processing nutrients generates heat. It has traditionally been assumed that inadequate feed intake caused by the thermal load is responsible for decreased milk production (Fuquay, 1981; DeShazer et al., 2009).

When daily average THI for the day (24hr period) is equal to or above these levels.

THI 70 (23.5°C) - Milk urea nitrogen (MUN) increases

THI 68 (22°C) - Milk protein yield declines

THI 65 (20°C) - Conception rate declines

THI 57 (14°C) - Oestrus activity reduces

Strategies for Mitigation

Management strategies can include:

• Adequate water availability

• Ensuring feed is fresh and pushed up

• Fitting fans

• Ensuring adequate shade for grazing cows

• Equaliser® CoolCow to help improve cow comfort and maintain feed intake, milk production and fertility

  
  

Looking Ahead

Have you ever considered introducing Equaliser® CoolCow to your herd?

Equaliser® CoolCow helps body cells to maintain hydration during temperature fluctuations to help improve cow comfort and maintain feed intake, milk production and fertility.

For more information about Equaliser® CoolCow contact your local DN Sales Specialist or call our team on 01200 420201.

DN Sales Specialist