The hidden threat:
understanding and managing oxidative stress in livestock
Key take-away
Oxidative stress, resulting from an imbalance between antioxidant defenses and reactive oxygen species (ROS), is a critical challenge in intensive livestock farming.
Oxidative stress impacts animal health and productivity through multiple pathways: it
- compromises immune function,
- reduces gut health and nutrient absorption,
- damages vital organs like the liver and kidneys,
- and impairs reproductive performance
The effects extend to meat quality, causing issues such as increased drip loss, rapid discoloration, and muscle disorders. These impacts collectively lead to decreased animal performance and economic losses for farmers. Phytogenic products emerge as a promising solution, offering antioxidant, anti-inflammatory, and antibacterial properties that can help manage oxidative stress and support antibiotic-free production.
Oxidative stress explained
Intensive livestock farming exposes animals to various stress factors throughout their life cycle such as heat stress, weaning stress, toxins, pathogens and an unbalanced diet. The process that plays a central role in all these situations is oxidative stress, which results from an imbalance between antioxidant defenses and reactive oxygen species (ROS) in favor of ROS.
ROS are highly reactive compounds derived from oxygen that can damage cellular macromolecules, but they also play important roles in biological processes, acting as mediators of cell metabolism, inducing apoptosis, activating genes, serving as signaling molecules, and functioning as an essential part of the innate immune system. ROS originate from both endogenous sources (primarily the respiratory chain in mitochondria and immune cells) and exogenous sources (radiation, air pollution, chemicals, toxins, and certain feed components). As aerobic organisms are continuously exposed to ROS, they have developed antioxidant defense systems that scavenge and suppress ROS generation and repair damaged biomolecules. However, when ROS production exceeds the capacity of these antioxidant defenses, animals experience oxidative stress, which damages cell membranes, proteins, and DNA, ultimately impairing cell function and leading to cell death and structural tissue damage.
Inflammation and oxidative stress, a close link?
Reactive oxygen species initiate an intracellular signaling pathway inducing inflammation and the production of pro-inflammatory cytokines. Depending on the concentration of ROS the inflammation is either regulated or exaggerated. On the other hand, ROS are part of the inflammation process to combat infectious pathogens and contribute to the normal immune defense of the animal. Indeed, at the site of injury and inflammation, immune cells produce and liberate a high amount of ROS to destroy the pathogen, ultimately leading to oxidative stress. Thus, inflammation and oxidative stress are pathophysiological events that are tightly linked with one another. One of them may appear before or after the other, but when one of them appears the other one is most likely to follow and further aggravates the first. Both processes induce cell and tissue damage and take part in the pathogenesis of many chronic diseases.
How does oxidative stress impact the animal?
Immunosuppression
Oxidative stress contributes to immunosuppression by damaging immune cells and disrupting key immune functions.
Excessive ROS molecules can impair lymphocytes, macrophages, and other immune cells by damaging their membranes, proteins, and DNA, ultimately reducing their viability and effectiveness. Oxidative stress also interferes with immune signaling pathways, which are essential for coordinating immune responses and cytokine production.
When oxidative damage occurs, the body initiates inflammation to defend and repair affected tissues. This is an energetically costly process that diverts resources away from growth and immune function. As a result, the animal’s ability to fight infections and respond to vaccines may be compromised. Additionally, when antioxidant defenses are overwhelmed, the immune system becomes even more vulnerable, increasing susceptibility to disease and negatively impacting overall health and productivity.
Reduced gut health and digestion
Despite the protective barrier provided by the mucosa, the gastrointestinal tract remains prone to ROS attack as it harbors many potential sources of ROS. Reactive oxygen species can compromise the gut barrier by disrupting the tight junction proteins resulting in an increased intestinal permeability and facilitating the translocation of toxins (endotoxins, mycotoxins …) and pathogens.
In addition, animals experiencing oxidative stress exhibit reduced villus height and crypt depth, reducing the effectiveness of digestion and nutrient absorption.
Liver and kidney injury
The liver and kidney are organs that are highly vulnerable to damage caused by ROS. Like the gut, the liver and kidneys have tight junctions forming barriers that are compromised during oxidative stress. A variety of liver cells are highly susceptible to oxidative stress, leading to altered hepatic cellular function, inflammation and fibrosis.
Oxidative stress not only triggers hepatic cell damage by inducing permanent changes to lipids, proteins and DNA but more importantly, modulates pathways such as gene transcription, protein expression, cell apoptosis and liver cell recovery. These pathways regulate important processes in the liver and control normal biological functions. As these mechanisms become disrupted, the liver’s detoxification capacity may decline, reducing its resistance to harmful substances such as endotoxins and mycotoxins.
With regard to the kidneys, ROS invade the renal tissue and degrade key structures in the kidney involved in the excretion of a variety of waste products produced by cellular metabolism into the urine.
Impaired reproductive function
High ROS levels can damage all cell types in the body, including reproductive cells such as sperm and oocytes (eggs).
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- In females, damaged oocytes may not mature properly, have reduced fertilization potential, or develop into poor-quality embryos.
- In males, oxidative stress reduces sperm motility and alters morphology, affecting overall sperm quality.
Additionally, oxidative damage to sperm DNA can compromise fertilization and early embryonic development, increasing the risk of embryo loss. Oxidative stress also disrupts the synthesis, secretion and action of reproductive hormones in both sexes, interfering with essential processes such as follicle development, ovulation and sperm production.
Furthermore, the cells that make up the tissue of reproductive organs can be damaged by oxidative stress, negatively affecting their function. For example, excessive ROS can compromise uterine health and placental development, leading to insufficient supply of nutrients and oxygen to the embryo, and raising the risk of complications and fetal loss.
Meat quality issues
Another consequence of excessive ROS production is a decline in meat quality. Oxidative stress damages proteins and lipids in muscle tissue, compromising the structural integrity of the meat and reducing its ability to retain moisture. As a result, drip loss during processing and cooking increases, leading to drier meat and reduced consumer satisfaction. Lipid peroxidation further accelerates spoilage, significantly shortening the shelf life of meat products. In addition, animals under oxidative stress have lower antioxidant levels and higher ROS concentrations in their muscle tissue. These ROS remain active after slaughter and speed up the oxidation of myoglobin and other pigments, causing the meat to discolor more rapidly and not look fresh or appealing. Additionally, oxidative processes damage collagen, a key component of connective tissue, negatively impacting tenderness and overall meat quality. In poultry, oxidative stress is closely linked to muscle disorders such as wooden breast, spaghetti meat, and white striping, all conditions that further compromise texture, appearance, and market value.
Reduced growth and productivity
In addition to the meat quality issues described above, oxidative stress significantly impacts animal performance across different species. The induced inflammation, together with the repair of damaged tissues requires energy and redirects nutrients away from growth and production processes, resulting in economic losses for farmers.
Moreover, pro-inflammatory cytokines suppress appetite resulting in a reduced nutrient uptake for production purposes.
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- In poultry, oxidative stress negatively affects egg production and compromises eggshell quality.
- Similarly, dairy cows experiencing oxidative stress show decreased milk production and reduced milk quality.
Managing oxidative stress with phytogenics
Phytogenic products, which are derived from plants, have already proven their effectiveness in medicinal applications. Recently, several studies have revealed their effectiveness in counteracting oxidative stress in production animals as well, and ascribe it to their antioxidant, anti-inflammatory, and antibacterial properties. These natural compounds contain various bioactive substances like polyphenols, flavonoids, and essential oils that can neutralize free radicals and suppress inflammatory pathways.
Their antibacterial properties help maintain a healthy gut microbiome by inhibiting the growth of harmful bacteria while promoting beneficial bacteria. Furthermore, incorporating phytogenic products into animal feed has been shown to enhance digestion by stimulating the production of digestive enzymes and strengthening intestinal tissue morphology, thereby optimizing nutrient absorption and utilization.
These properties make phytogenic products particularly valuable during challenging periods where animals are more susceptible to oxidative stress, such as during heat stress, pathogen exposure, weaning or feed transitions. Thanks to this comprehensive range of benefits, phytogenic products are found to improve growth and animal health, and are considered a strategic component in antibiotic-free production.
References are available upon request.
