HEAT STRESS – affects growth rate, fertility and the reproductive herd

Sue Bernhardt-Smith

As we know, heat stress in sows leads to a reduction in feed intake, milk production, body weight loss and reduction in the growth rate of the litter.

Like all our seasons, Summer comes with its own challenges. Heat stress conditions also affect the sow’s subsequent reproductive cycle; recognised as longer intervals between weaning and estrous or, at times, fail to return to estrous. Embryo losses are also recognised during heat stress conditions, consequently reducing the farrowing rate and the total number of pigs born. First time in-pig gilts are purportedly most at risk.

To ensure that our in-pig sows/gilts and nursing sows are comfortable we can ensure that farrowing arks have a through breeze (easily managed if there is an opening at the rear of the ark), sprinklers, shallow wallows, shade and if inside, again, sprinklers, fan and copious amount of fresh drinking water. Feeding in the early morning and late evening when cool. During heat stress, our pigs increase respiration rate and redirect blood flow from tissues and organs to the skin to transfer metabolic heat to the environment. The redirection of blood causes a cascade of adverse effects such as dehydration, organ injury, gut permeability and inflammation.

Should you suspect your sow/gilt/boar/weaners being heat stressed, such as, breathing rapidly with 35 breaths per minute or more, dunging in pen/ark and lying in their own urine, DO NOT THROW A COLD BUCKET OF WATER ON TO YOUR PIG, but place a soaked towel onto your pig around the tummy, ears and neck.

Our weaners/fattening/finishing stock will also suffer as their appetite will decrease and as a result you may witness some of your weaners falling back a little. Firstly, dont beat yourself up about it you are doing nothing wrong. To aid a good appetite, again feed in the cooler parts of the day and ensure there is copious amount of shade, please ensure wallows are topped up and there is copious amount of fresh drinking water. Routine and observing your herd is key. This week the country will be on Amber weather warning from Thursday (11 August 2022) through to Sunday (14 August 2022) with temperatures soaring to 35 degrees C which in Farhrenheit is 95 (which is my preferred reading).


May be an image of animal and outdoors
Dawn Horler

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