Selenium is a tiny but mighty nutrient that helps farm animals stay healthy, especially around pregnancy and birth. Scientists have discovered that selenium works like a bodyguard, protecting animals from stress and infection while keeping their reproductive systems working properly. This review explains how selenium does its job at the cellular level and suggests it could be a simple, natural way to prevent common health problems in livestock. The research shows promise for both male and female animals, though scientists say we need more studies to figure out the best doses and forms to use.

The Quick Take

  • What they studied: How selenium, a nutrient found in food, helps farm animals stay healthy and reproduce better, especially during pregnancy and birth when they’re most vulnerable
  • Who participated: This is a review article that looked at existing research about selenium in livestock (cattle, sheep, pigs, etc.) rather than conducting a new experiment
  • Key finding: Selenium appears to protect farm animals by reducing harmful stress in their cells, boosting their immune system, and preventing infections that can damage reproductive health
  • What it means for you: If you work with livestock, adding selenium to animal feed might help prevent pregnancy problems and infections naturally. However, the right amount matters—too little doesn’t help, and too much could be harmful. Talk to a veterinarian about whether your animals need more selenium

The Research Details

This is a review article, meaning scientists read and summarized all the existing research about selenium and farm animal reproduction. They looked at how selenium works inside animal cells, what happens when animals don’t get enough selenium, and what benefits they see when selenium is added back to their diet.

The researchers focused on a critical time period called the ‘periparturient period’—the weeks around pregnancy and birth when farm animals are most stressed and their immune systems are weakened. They examined both male and female animals to understand how selenium helps each one differently.

The scientists also looked at different forms of selenium (like regular selenium and nano-sized selenium particles) to see if some work better than others, and they explored the molecular mechanisms—basically, the tiny chemical processes inside cells that make selenium protective.

Understanding how selenium works at the cellular level helps farmers and veterinarians make better decisions about animal nutrition. Rather than just knowing ‘selenium is good,’ this research explains the actual mechanisms, which helps determine the right dose, the best form to use, and which animals benefit most. This knowledge could prevent expensive health problems before they start.

This is a review of existing research rather than a new experiment, so its strength depends on the quality of studies it examined. The authors acknowledge that more large-scale studies are needed, especially studies designed specifically for different animal species. The research is current (2025) and published in a peer-reviewed journal focused on animal reproduction, which adds credibility. However, readers should know that some of the proposed mechanisms are still being studied and aren’t completely proven in all livestock species yet.

What the Results Show

Selenium appears to work like a cellular protector in farm animals. It gets incorporated into special proteins called selenoproteins, which act as antioxidants—think of them as tiny cleanup crews that remove harmful substances called free radicals that build up during stress and pregnancy.

When farm animals don’t get enough selenium, especially around birth, their bodies produce harmful substances (BHBA and NEFA) that trigger inflammation and weaken the immune system. This leads to infections in the uterus and udders. Adding selenium back appears to flip a switch in cells that reduces inflammation and boosts immune defenses.

In female animals, selenium seems to help repair the uterine lining, regulate hormones, and maintain immune tolerance (the ability to accept the pregnancy without attacking it). In male animals, selenium combined with vitamin E improves sperm quality, movement, and testosterone levels—basically making sperm healthier and more active.

The research also suggests selenium influences how genes are turned on and off, potentially reducing genes that cause inflammation.

Additional findings include selenium’s role in ovarian follicle development (the structures that produce eggs) through special receptors in the ovaries. The form of selenium matters—organic forms and nano-sized particles may work better than traditional forms. The benefits appear to vary depending on the animal species, how much selenium is given, and the animal’s current health status.

This research builds on decades of knowledge about selenium as an essential nutrient. Previous studies showed selenium prevents deficiency diseases, but this review goes deeper, explaining the specific molecular pathways involved in reproductive health. It connects selenium to newer concepts like epigenetics (how genes are controlled) and specific immune pathways, representing an evolution in our understanding from ‘selenium is necessary’ to ‘here’s exactly how it protects reproduction.’

The authors clearly state that most research has been done in laboratory settings or small studies. Large-scale, real-world studies in different livestock species are still needed. The optimal dose for different animals isn’t firmly established. Some of the proposed mechanisms are based on cellular studies and may not work exactly the same way in living animals. The review focuses mainly on livestock, so findings may not apply to other animals. Additionally, the best form of selenium (regular vs. nano-particles) and delivery method still need more research.

The Bottom Line

Based on moderate evidence: Selenium supplementation may help prevent reproductive problems in livestock, especially during pregnancy and birth. Moderate confidence: Combined selenium and vitamin E supplementation appears beneficial for male fertility. Low to moderate confidence: Nano-selenium forms may work better than traditional forms, but more research is needed. Always work with a veterinarian to determine if your animals need selenium supplementation and at what dose, as requirements vary by species and diet.

Livestock farmers and ranchers should pay attention to this research, especially those experiencing reproductive problems like infertility, pregnancy loss, or infections after birth. Veterinarians specializing in livestock reproduction should consider this information when advising clients. This research is less relevant for pet owners or people not involved in livestock production, though the basic science may interest those curious about animal nutrition.

Improvements in reproductive health from selenium supplementation typically appear over weeks to months, not days. The most noticeable benefits usually show up in the next breeding season or in animals born after supplementation begins. Preventing problems is easier than fixing them, so starting supplementation before the critical periparturient period is ideal.

Want to Apply This Research?

  • If managing livestock, track selenium supplementation dates and doses, then monitor reproductive outcomes: pregnancy rates, miscarriage rates, infection rates after birth, and sperm quality in males. Compare these metrics before and after supplementation begins.
  • Work with your veterinarian to assess your herd’s selenium status (through blood tests or diet analysis), then implement a consistent supplementation protocol. Set reminders to administer supplements on schedule and record which animals receive them.
  • Maintain a long-term log of reproductive health metrics (conception rates, birth complications, mastitis cases, sperm quality) to evaluate whether selenium supplementation is making a real difference in your specific herd. Adjust doses or forms based on results and veterinary guidance.

This review summarizes scientific research about selenium in livestock reproduction but is not a substitute for professional veterinary advice. Selenium requirements vary by animal species, age, diet, and health status. Before starting any supplementation program, consult with a veterinarian or animal nutritionist who can assess your specific animals’ needs and recommend appropriate doses. Excessive selenium can be toxic, so proper dosing is essential. This information is intended for educational purposes and should not replace professional veterinary guidance for diagnosing or treating reproductive problems in livestock.