Heat stress in livestock - by Dr Norman Weatherup, Senior Beef & Sheep Technologist, CAFRE, Greenmount Campus
Date published:
Beef animals that are almost finished are at the most risk of heat stress as they have the least amount of lung capacity relative to body weight.
Animals that are very young and very old also are at increased risk. They do not have the physiologic reserves to withstand prolonged periods of heat.
Ensure animals have access to plenty of clean water as water intake increases markedly in hot weather. Evaluate water supply lines and ensure you have sufficient water pressure and flow capacity available to keep troughs full during times of peak water consumption.
At 30+ degrees dairy cows will drink 110+ litres per day at 14 litres per minute when at the trough so space and flow rate are essential to ensure this level of water consumption is achieved.
Increase feed rates and introduce buffer feeding to dairy cows to maintain milk yields as grass growth rates fall sharply due to a moisture deficit.
Move the animals’ feeding time to late afternoon or evening to allow rumen fermentation to take place during the cooler night temperatures. This will also increase lung capacity for the cattle during the hotter daytime temperatures. Normal digestive processes create heat in cattle. This body heat reaches a maximum several hours after the meal is consumed. When feeding cattle in the morning of high-heat-stress days, producers may be matching peak environmental temperature with peak body temperature from digestion. Altering feed deliveries accordingly can avoid some potential additional heat from digestion.
If feeding once daily, consider moving feed delivery until the afternoon. If feeding multiple times daily, consider feeding a small meal in the morning and a larger portion of the diet later in the afternoon. Decrease the amount of feed offerings during and for several days after heat stress. Effects of heat stress may linger, and rapidly increasing feed deliveries will increase metabolic heat production and possibly cause problems even though the environmental heat index has dropped below the typical heat stress threshold.
Provide shade if possible as solar radiation from sunny, clear skies contributes to body temperature in cattle and sheep.
Do not handle livestock during temperature extremes. If handling livestock is absolutely necessary, keep working time as short as possible, use calm animal-handling techniques to minimize stress related to handling, and consider running smaller groups through the facility or into holding pens. Provide sufficient water in holding pens. Get started as early in the morning as daylight will allow. Do not work in the evening after a heat-stress day as livestock need this time to recover.
Pig producers must continue to check that all fan ventilation equipment is working properly. Also pigs must have access to good quality drinking water at all times, so flow rates in all water nipples must be regularly checked. Keep stocking rates to a minimum and plan ahead, especially with reduced kill in processing plants during the July holidays.
Feed intakes for pigs and poultry will be much lower in high temperature and growth rates reduced and producers need to plan ahead again.
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