Heat stress arises whenever animals are exposed to a temperature higher than its “thermoneutral zone.”.
We can define as a thermoneutral zone a temperature range within which the animal does not manifest the characteristic symptoms of heat stress because it can still maintain its body temperature constant by displaying normal behavior.
The thermoneutral zone for laying hens is between 19 and 22° C, while for broilers, it is between 18 and 22° C.
In general, poultry shows similar heat stress behaviors with individual variations in intensity and duration of the response.
Animals suffering from heat stress
The animal’s high metabolic activity for growth or egg production results in increased heat production.
This heat production depends on several factors, including Race, body weight, more or less thrust production, ingestion, type of food and exercise.
Dissipating this heat in poultry is not easy since, unlike mammals, they do not have sweat glands. When the external temperatures exceed the thermoneutral zone of the animal, the mechanisms used for the dispersion of heat are less and less, and the consequences can be harmful.
Heat dispersion in poultry species can occur through five main mechanisms:
The effects of heat stress depend on the duration and frequency of the animal’s exposure to the stressful event.
Exposure to high temperatures can be acute and sudden or chronic as during the summer cycles where the animal is exposed to temperatures well above the thermoneutral zone for prolonged periods.
Chronic exposure does not exclude acute exposure and vice versa; however, while an increase in mortality accompanies acute exposure, often due to suffocation, chronic exposure is accompanied by a decline in performance due to oxidative stress That incurs in the animal.
One of the responses to heat stress we have seen is to disperse the heat through the exchange of the same with the surrounding environment. To do this, the animal’s physiological response is to increase the peripheral blood flow through the dilation of the blood vessels of superficial tissues such as the skin, to the detriment of visceral tissues, thus reducing the flow of blood to internal organs such as the intestine.
The resulting state of hypoxia generates several reactive oxygen species (ROS), commonly known as free radicals, which are greater than the animal’s ability to eliminate.
What is created is what in technical jargon is called an oxidative stress state. The direct consequence of this state is cell damage, with loss of the structural integrity of the intestine, local inflammatory response and alteration of the immune response.
With the alteration of the intestinal barrier, there are also negative changes in the intestinal microbiota (the population of microorganisms that populate the intestine and which is essential for the maintenance of certain functions of the intestine).
The combination of these alterations creates a syndrome called “leaky gut syndrome”. This syndrome is described as an alteration of the structural integrity of the intestine. Consequently, it has an excessive loss of fluids which inevitably results in poor assimilation of food, loss of food efficiency, conversion and performance.
The primary weapon available to the breeder is to prevent oxidative stress from occurring, avoiding heat stress.
Below are some tips for the farmer that can be useful to reduce the production of endogenous heat in the animal and promote heat loss.
From the point of view of nutrition, on the other hand, the breeder can intervene by integrating mineral salts and electrolytes into the drinking water that are lost when the leaky gut syndrome occurs.
Another intervention that can be carried out is to integrate the diet with substances with antioxidant action from plants and derivatives and vitamin C, which work in synergy to counteract the adverse effects of free radicals produced in the course of oxidative stress. We have seen it to be the direct consequence of heat stress.
In this regard, Tecnozoo recommends NORMOTERM FLUID, which, thanks to the contribution of natural substances with antioxidant action, helps counteract alterations in the oxidative balance, maintaining the physiological balance of the animal, especially in stressful situations.
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