December9 , 2022

How can heat stress affect the quality of poultry meat?

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How can heat stress affect the quality of poultry meat?

Genetic selection towards faster growing birds and higher breast yield has made the modern broilers more vulnerable to high temperatures. It is known that nowadays the negative effects of heat stress in commercial strains are observed at lower temperatures than several decades ago.

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Besides the negative effects of heat stress on the oxidative status of the animals, egg quality, reproductive performance, gut health and immune response, exposure to high temperatures also impairs the quality of poultry meat.

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Read also: Enhancing broiler growth with blood meal

Three ways in which heat stress reduces the quality of poultry meat

1. Rapid drop in pH after slaughter

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The pH changes in the muscle during the first 24 h after slaughter are important for the quality of the meat, because a very low pH or a relatively low pH combined with a high temperature of the carcass will lead to protein denaturation.

Whenever proteins are denatured, the muscles can not hold water and the meat appears pale, soft and exudative.

In normal conditions, after slaughter the metabolism in the muscles continues for a certain time. During this post-mortem period the glycogen is transformed into lactic acid through a process called glycolysis, which lowers the pH.

In heat stressed birds, glycolysis is accelerated, leading to a very low pH in the muscle, while the temperature of the carcass is still high due to the hot environment.

Damage by free radicals

Poultry and poultry meat are particularly susceptible to oxidative reactions. As we explained in this article, high temperatures increase the oxidative stress of the birds, causing:

Oxidation of the muscle proteins, that leads to poor water retention, bigger losses during cooking, less juiciness and decreased tenderness.

Oxidation of lipids, which worsens flavor, color, texture, nutritional value and acceptability in meat, while reduces its shelf life. Moreover, free radicals damage the liver and alter lipid metabolism, leading to more deposition of fat in the abdomen and less in the muscles.

Increase of microbiological contamination

The risk of carcass contamination by foodborne pathogens, such as E. coli and Salmonella, increases during the episodes of heat stress. There are two main reasons:

Heat stressed birds are more prone to digestive infections, due to more challenges by pathogens and mycotoxins during hot weather, in addition to the immunosuppression associated with heat stress.

During heat stress the intestinal integrity is impaired, leading to intestinal permeability (leaky gut) and the spread of digestive pathogens to other organs.

Read also: How to reduce chicken coop/poop odour

Essential oils prevent the damages caused by heat stress in poultry meat

The administration of essential oils, especially during the finisher stages, improves the quality of the carcass after slaughter:

Raising the pH of the meat: it has been observed in several field trials that administering phytobiotics during all the life of the bird, and specially during the finisher stage, leads to a higher pH of the meat at slaughter. In a trial that we made recently (unpublished), we observed a higher pH in the breasts and legs of broilers that had been given PhytoShield©.

Neutralizing free radicals: antioxidant essential oils relieve oxidative stress and prevent the damages in the proteins and fats, reducing water losses and the amount of malondialdehyde in meat (by-product of fat oxidation).

Preventing microbiological contamination of the carcass: plant extracts and essential oils kill digestive pathogens, prevent leaky gut and are excellent immune boosters.

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