Selenium (Se) is a naturally occurring trace element found in water and some foods and is essential for human and animal cellular function. In food producing animals, selenium supplementation can affect productivity (weight gain, milk yields and fertility) as well as health. If over supplied, Se can also be highly toxic. There is a maximum legal limit of 0.5mg/kg selenium in animal feed with no more than 0.2mg/kg being derived from organic sources.
As well as effects on productivity, Se is also suggested to have antioxidant, anti-inflammatory, anti-carcinogenic, potentially antiviral, and antibacterial activity when included in the diet. A recent review by Pecoraro et al. (2022) looked at the potential health benefits of selenium in food animals, with a particular focus on pigs.
The ability to fight infection is closely linked with the nutritional status of an animal and it’s now thought selenium deficiency may affect the pathogenicity of a virus rather than just affecting immune function. Oxidative stress occurs during viral, bacterial and environmental challenges, the potentially antiviral action of selenium is linked to selenium’s role as an antioxidant. In other species, viral shedding was reduced after using either selenium enriched yeast or sodium selenite, with the best results in the former. In lab tests using porcine circovirus (PCV2), a similar trend was documented where high levels of Se blocked the virus from replicating. In pigs under heat stress, selenium supplementation may help manage gut inflammation and help protect against damage to the gut lining. The research investigated by Pecoraro et al. (2022) suggested that blood concentrations of Se decreased when pigs were challenged, which led to the question...
The transfer of selenium from the sow to the piglets is limited and selenium concentrations in older sows milk are lower, thus piglets born to higher parity sows are suggested to have a lower selenium status at birth and weaning. Attempts to increase selenium levels in colostrum and milk via the sow’s diet have found better results when feeding organic sources of selenium than inorganic sodium selenite. The greater absorption noted between inorganic and organic Se sources has been recorded across all pig classes.
Organic sources also appear to be less toxic compared with inorganic sodium selenite, but organic sources are more expensive than sodium selenite, up to 400% more expensive!
Whilst this review found evidence supporting claims of selenium having health protecting properties in pigs, most interestingly the antiviral protection in pigs, the review highlighted the need for more ‘in pig’ research in this area.
For the full scientific review please see
https://jasbsci.biomedcentral.com/track/pdf/10.1186/s40104-022-00706-2.pdf