Best practices for cooling your herd

10 june 2021

Hot, humid summer days can be really uncomfortable for your cattle, but also for you, as farmers. In fact, animals are affected by heat stress every summer.

Heat stress occurs when cattle, with a comfort temperature of between 6 and 20°C, generate and absorb too much heat. Breathing and sweating are no longer enough to regulate their body temperature and get rid of the excess heat.

Heat stress can have serious consequences for your animals’ health and also for your finances. That’s why we have decided to revisit the problem in this article to make a situational analysis (causes, symptoms, consequences) and to highlight the repercussions and best practices to be applied to actively combat heat stress.

The causes

There can be many causes of heat stress:

• Cattle are heat stressed when the heat load on the animals is greater than their ability to dissipate heat.
• A combination of high air temperature, high humidity, high solar radiation and little air movement increases the risk.
• High relative humidity decreases evaporation and reduces cows’ ability to shed heat by sweating or breathing.
• When the air temperature is above 21° and the humidity is greater than 70%, the animals start to reduce their feed intake. As a result, milk production is reduced.
• Cooler nights are needed so cattle can get rid of some of the heat and reduce their body temperature. Conversely, hot, cloudy nights are considered an aggravating factor, as they reduce the cooling period and increase the risk of heat stress.

The symptoms

As in humans, the effects of heat and lack of water on cattle include headaches, irritability and lethargy. Ruminants use a variety of strategies to cope with hot weather:

• Increased breathing rate and sweating; 
• Increased water consumption – heat-stressed cattle drink almost twice their usual amount of water;
• Reduced food intake; 
• Reduced milk production;
• Change in the composition of the milk – the fat and protein content noticeably decreases;
• Change in the concentration of hormones in the blood, e.g. triggering an increase in the blood level of prolactin (the hormone responsible for making milk);
• Development of leaky gut syndrome: this is damage to the lining of the intestine, which becomes porous. This can lead to bacteria or other toxins from the contents of the intestine entering the bloodstream and causing infections. Absorption of nutrients will also be reduced.
• Behavioural changes: seeking shade or a place to cool off; cattle gathering together to shade one another; refusing to lie on the ground; changing location depending on the orientation of the sun; standing or lying in water or next to water tanks. 

The consequences

• Reduction in appetite and therefore in food intake (8 to 12%). This results in a decrease in the production of volatile fatty acids in the rumen, which, in turn, leads to a fall in milk production;
• Reduced buffering capacity of saliva, resulting in frequent shortness of breath;
• Reduced fertility (increase in cell count);
• Great variance of pH in the rumen;
• Higher risk of acidosis if a sustained drop in rumen pH occurs.

Tips and good practices to prevent heat stress

In order to help you minimise the impact of heat stress on productivity and ensure the comfort of your cattle during the summer, we have compiled a list of key points below.

PRIORITY
Remember to check and, if necessary, cool the most sensitive animals first. By most sensitive we mean those which have just calved, as well as high-producing and late-lactating cows.

WATER
Dairy cows will require more than 100 litres of water a day each and will drink between two and six times a day. Make sure the water delivery rate of your tanks is high enough to meet your herd’s needs so that they never run out. Most cows are very thirsty after milking. Install water troughs with enough space to accommodate cows as they leave the parlour. Make sure the tanks are always clean.

FEED
Ensure your cows have high-quality summer pasture. Feeding a high-fibre diet can increase the heat of fermentation in the rumen, thereby increasing the heat load.
You can add our Math's Fresh TMR to the food ration before feeding. The acids inhibit the growth of yeast and moulds, reducing nutrient loss and the heating of the feed. 

FOOD SUPPLEMENT
At Nutriprof, we have developed Math's Buf Balance: a unique blend of ingredients to neutralise ruminal acidity. Math's Buf Balance is a high-quality buffer that starts working immediately after administration, but which also has a long-term effect. It improves animal performance, maintains or improves milk quality and also works quickly and effectively on heat stress problems. 

SHADE
Outdoors, try to use meadows with trees and shade. Ideally, five square metres of shade per animal is recommended to prevent competition. Ensure outdoor feeding areas are shaded, installing awnings if necessary. In open buildings, be sure to create additional shaded areas.

ORGANISATION
Reduce the herd’s distance from the milking area and their walking speed going to and from it. Drastically reduce the time they spend in unshaded areas. Isolate the most severely heat-stressed cattle and provide maximum shade and cooling for them. Milk earlier in the morning and later in the evening. Divide your herd into smaller groups for milking. 

COOLING

Misting
Misters with a minimum flow rate of three litres of water per minute can be used in the milking area to humidify the cows and help with evaporative cooling after milking. In the milking parlour, which is considered a priority area for cooling, a large shower (5-10 litres per animal) can be considered. This is much more refreshing for the animals. Spraying frequency should increase proportionally with rising temperatures. The effectiveness of water misters depends on the evacuation of water vapour by air movement, ideally using a fan. In fact, if the sprayed water drops are not properly stirred by air movements, they can cause ambient humidity, which could aggravate heat stress (cf. Chapter on causes).

Ventilation
Fans can be placed in various locations to create high air circulation and limit humidity in areas where showers or misters are installed: in the milking parlour and above the cubicles and feeding alleys. Maintain a distance of 10 times the width of a fan between each fan.

Cooling strategy
The cooling strategy is based on the temperature and humidity index, given by the following calculation: THI = 0.8T + (RH x (T-14.4)) + 46.4 In this formula, T is the maximum temperature of the day expressed in degrees Celsius and RH refers to the relative humidity percentage divided by 100.

THI (temperature and humidity index) from 68 to 71 = effective ventilation

THI between 72 and 79 = ventilation and misting or shower depending on the humidity

THI greater than 79 = effective ventilation and shower (big drops)

BUILDINGS
Design buildings to promote air circulation. For this purpose, choose low side walls with adjustable curtains. Choose an open ridge for faster removal of warm air and avoid transparent sheets to limit the heating of the building by solar radiation.