Heat stress – the hot topic that needs to be taken seriously

Written by Dr. Kevin B.H. Teh (DVM)

Economic losses due to heat stress in the livestock industry amount to billions of dollars per year throughout the world. Heat stress affects almost all production parameters of livestock including growth, reproduction, egg, milk and meat production as well as immune status. This can cause a severe economic burden to producers who rely heavily on these livestock populations for securing their livelihoods.

When is hot too hot?

Animals possess several adaptive mechanisms to cope with heat stress challenges, but these mechanisms only help the animals survive the stress by compromising the productive responses.

The first sign of heat stress is increase in breathing, panting and sweating.  As the heat stress becomes severe, the animal can be observed to have a lack of coordination and trembling. When an animal goes down, most likely at this stage the animal will not be able to get back up.

Heat stress isn’t cool

Heat stress can be exacerbated by several factors, such as lack of shading and poor drinking water quality. Hot weather and high humidity can reduce feed intake, weight gain, reproductive efficiency, milk and egg production; while increasing susceptibility to diseases. Changes in behaviour and even death can also occur.

The first and foremost impact of heat stress is on the growth performance of livestock. This could be attributed to the reduced feed intake of a heat stressed animal, as its’ body reduces heat production in an effort to cope with the external environment temperature.

By far, the most significant adverse impact of heat stress arises on the reproductive efficiency of the livestock. Heat stress not only affects the quantity and but also the quality of milk and egg production.

Heat stress also compromises the immune system in livestock making them susceptible to various disease conditions. The animal compromises its productive efficiency in an effort to support life-sustaining activities during heat stress exposure.

Rehydration – getting water back in the body

Water is not only one of the most important nutrients in animal nutrition, but also plays an essential role promoting heat dissipation, especially under hot conditions.

Water accounts for 50 to 80 percent of a livestock’s weight and is involved in every physiological process. Without water, feed intake greatly decreases, the animal becomes dehydrated and body functions fail.

Water availability and quality can become a major issue during hot weather. An adequate supply of clean drinking water is important to helping livestock maintain a safe body temperature. When it is hot and humid, consuming water is the only way livestock can cool down. When water quality is poor, most livestock reduce their water intake which reduces performance. In critical heat stress situations, water loss may cause marked changes in the thermoregulatory balance of the livestock

and may result in death. Good water quality can increase water intake and improve livestock production.

ZamiGuard Clean Water is a stable and pure solution of chlorine dioxide, the best available disinfectant for the removal and prevention of biofilm and the elimination of pathogens in drinking water. ZamiGuard Clean Water has a broad biocidal action and effectively prevents and eliminates pathogenic microorganisms in water. ZamiGuard Clean Water aids in improving water and feed intake in livestock which may improve livestock performance.

Beat the heat

Poultry are very sensitive to heat stress. A small temperature variation could quickly become

lethal. High mortality, lower body weight gain, reduction in egg production and poor eggshell quality are common adverse effects of heat stress often seen in broilers and laying hens 1. Approaches to overcoming the detrimental effect of high temperatures include modifying the diet. Studies with bacitracin have suggested it may play an important role in improving the adverse consequences of heat stress.

ZAMBACZN150 is a highly effective form of bacitracin for the prevention and control of Clostridium perfringens in poultry. Bacitracin significantly reduces the energy maintenance requirement and improves heat tolerance in poultry 2, 3. This leads to improved survival, growth rate and feed efficiency in broilers and improved egg production and egg quality in layers 2, 3.


  1. Lara LJ, Rostagno MH. Impact of Heat Stress on Poultry Production. Animals (Basel). 2013;3(2):356–369. Published 2013 Apr 24. doi:10.3390/ani3020356
  2. Bronsch, K. and K. Männer. 1988. Effect of zinc bacitracin on energy metabolism in fowls. Berliner und Munchener Tierarztliche Wochenschrift 101: 150–153
  3. Ma ̈nner, K., and K. Wang, 1991. Effectiveness of zinc bacitracinon production traits and energy metabolism of heat-stressed hens compared with hens kept under moderate temperature. Poultry Sci. 70:2139–2147

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