*Mokshata Gupta, Ram Dev Yadav, Raju Kushwaha, Avinash Kumar
In the dynamic world of dairy farming, a silent revolution is underway, transforming the well-being of livestock and the quality of dairy products. At the heart of this revolution is selenium, a trace element that plays a pivotal role in enhancing antioxidant levels, boosting productivity, and ensuring reproductive health in dairy cattle. It is found in the environment in the soil. Its content in the forage largely depends on the location, soil conditions, species of plant, use of fertilizers, etc. Its presence in inorganic forms like selenites and selenates, as well as in organic forms like selenoamino acids (e.g., selenomethionine and selenocysteine), seleno-peptides, and seleno-proteins, underscores its versatile nature.
The mineral’s significance extends to the realm of immune response, where selenium deficiency is linked to a weakened immune system. Selenium administration has been observed to reduce inflammatory activity within the body. The repercussions of selenium deficiency are reflected in diminished GPx activity, compromised neutrophil function, DNA damage and heightened susceptibility of cells to oxidative damage due to disruption of membrane integrity.
Importance of Selenium
- It is a component of gluthathione peroxidase, an enzyme, protecting cell membrances from oxidative damage by neutralizing lipid damaging peroxides. The measurement of gluthathione peroxidase levels in blood serves as a indicator of selenium status.
- It has a sparing effect on vitamin E by ensuring normal absorption of the vitamin.
- It reduces the amount of vitamin E required to maintain the integrity of lipid membranes & aids the retention of Vitamin E in plasma.
- It exhibits a spectrum of beneficial effects like anti-inflammatory, antimutagenic, anticancer, antiviral, antibacterial, antifungal, and antiparasitic properties.
- It regulates gene expression associated with lipid activity, controlling excessive fat mobilization and lowering the risk of ketosis and fatty liver.
- It is involved in the synthesis, metabolism, and function of thyroid hormones.
Role of Selenium in Oxidative Stress
Redox reactions in cellular processes give rise to highly reactive by-products, namely reactive oxygen species (ROS) and reactive nitrogen species (RNS). Exogenous sources of ROS, such as xenobiotics (drugs, contaminants, toxins), along with factors like UV radiation, contribute to redox processes within the body. Reduced dietary intake of selenium or other antioxidants leads to accumulation of free radicals and the initiation of oxidative stress.
Selenium, as a crucial component of antioxidant enzymes, acts as a guardian against oxidative stress that causes cell damage and aging. Oxidative stress is the major contributor to various diseases in dairy cattle, including metabolic issues, inflammatory challenges like mastitis and metritis, ketosis, parasitic infections, and reproductive disorders. The provision of selenium is indispensable for cattle, as it transcends the placental barrier during pregnancy, playing a pivotal role in intrauterine and calf development. An ample Se supply enhances the antioxidative status, thereby contributing to an overall improvement in the health of dairy cattle.
Selenium orchestrates the regulation of pivotal antioxidant genes, including GPX, CAT, SOD, and GSH, mitigating oxidative stress in the process. The SOD gene, by quenching the superoxide radical and facilitating its transformation into less harmful hydrogen peroxide, actively curtails oxidative stress. This cascade is further complemented by the enzyme catalase (CAT), which dismantles hydrogen peroxide into water and oxygen, preventing DNA damage.
Oxidative stress within the mammary gland due to accumulation of free radicals causes decline in the number of mammary epithelial cells. Conversely, maintaining a balanced Se supplementation regimen mitigates hydrogen peroxide concentration in these cells, thereby alleviating oxidative stress and subsequently reducing apoptotic cell count.
Role of Selenium in Reproduction
From improving fertility to ensuring healthy pregnancies, selenium’s plays a vital role. Oxidative stress, a crucial factor in sperm fertility, induces lipid peroxidation that adversely affects the sperm plasma membrane. The high concentration of polyunsaturated fatty acids in the membrane makes it particularly susceptible, leading to compromised membrane fluidity and integrity. This, in turn, impacts sperm count, motility, and ultimately, their ability to fuse with oocytes. This leads to a cascade of reproductive challenges such as infertility, anestrus, retained placenta, occurrences of abortions and stillbirths. Additionally, oxidative stress-induced damage extends to sperm DNA, a pivotal factor in transmitting defective paternal DNA to offspring. The safeguarding of sperm membrane integrity and fertilizing capacity hinges on effective antioxidant protection.
Abortion occurs primarily due to insufficient concentration of progesterone, necessary for sustaining pregnancy. This can be overcome by selenium supplementation. In addition, its supplementation is also linked to improvement in gross and histological morphology of the testis, a reduction in metritis and ovarian cysts, as well as a decreased incidence of retained placenta.
Diseases Associated With Selenium Deficiency/Toxicity
Selenium & vitamin E has joint role in antioxidant system, immune function & imparting resistance to infections. Symptoms related to its deficiency & toxicity is as follows:
Selenium Deficiency
- Se deficiency in calves, lambs and dairy goat kids leads to a serious disease known as white muscle disease (WMD) or nutritional muscular dystrophy (NMD). This disease is manifested clinically by stiffness, weakness and recumbency. In pigs, mulberry heart disease is a frequent outcome.
- In young animals, WMD can also cause cardiac injury which results in sudden death within the first weeks after birth.
- The myopathy primarily affects the skeletal muscles and the affected animals have difficulty in standing and after standing, a trembling and staggering gait. The animals are unable to rise and weakness of the neck muscles prevents them from raising their heads.
Selenium Toxicity
- Animals grazing on plants that grow in seleniferous areas contain very high levels of selenium- causes Alkali disease (chronic poisonong) and blind staggers (acute poisonong).
- Symptoms include lethargy, stiffness of the joints, loss of hair from mane or tail, lameness, heart atrophy, anorexia, hoof deformities, etc.
- Acute poisoning, which results in death from respiratory failure, can arise from sudden exposure to high selenium intakes.
Selenium Supplementation
Assessing the selenium status in cattle is essential to formulate an appropriate supplementation regimen. It is crucial to regulate selenium inclusion in feed, as excess selenium from certain sources can be toxic. The supplementation of selenium in organic form is more efficient in enhancing growth parameters and antioxidant status in animals. The substantial sources of bioavailable organic selenium are selenium yeast, Brazil nuts, lentils, enriched wheat, Garlic and onion. Other sources includes organ meat, seafood, muscle meat.
Conclusions
Selenium’s role in bolstering antioxidant levels, boosting productivity, and ensuring reproductive health is reshaping the future of dairy farming. This quiet revolution holds the promise of not only healthier cows but also a more sustainable and prosperous future for the entire dairy industry.
“Elevate Life’s Essence: Empowering Wellness Through Selenium Supplementation.”