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Managing oxidative stress to improve piglet health

Piglets are born with very low levels of immune potential or antioxidants, which makes the young animals vulnerable to all kinds of pathogens. It is possible to give them a helping hand by feeding sows adequate sources of organic selenium.

By Pierre-André Geraert, Yves Mercier and Florian Couloigner, Adisseo, France

Without a doubt, weaning is certainly the most difficult period, not only for piglets but also for farmers. In traditional European swine production, piglets are weaned three to four weeks after birth. This time is stressful for piglets, having to face social stress with mixing with other piglets and changing from liquid feed with milk to solid feed.

These stressful conditions are frequently associated with digestive disorders due to gastro-intestinal tract immaturity leading to gut inflammation. In the worst cases, this can induce severe diarrhoea potentially leading to piglet death. Even under moderate stress conditions, however, without noticeable clinical problems, the induced inflammatory status is always accompanied by oxidative stress which severely impacts piglets during this period. In research, it has clearly been shown that oxidative status is exacerbated during the first week after weaning compared to suckling time without any visible clinical signs on the piglets. This weakened redox status appeared through a decrease of plasma vitamin C and vitamin E contents and an increase of oxidised-to-reduced-glutathione (GSSG/GSH) ratio and enhanced plasma Reactive Oxygen Species (ROS) levels. Moreover, newborn piglets have long been reported to exhibit a low vitamin E level and glutathione peroxidase (GPx) activity at birth.

Adequate feeding of the sows may provide antioxidant compounds such as selenium (Se) and vitamin E through colostrum to the piglets. Large variations, however, can be found between sows. Moreover, the contents of selenium and vitamin E appeared to rapidly decrease post partum: Up to 68 to 86%, one week after farrowing respectively. In addition, piglets from aged sows (older than fourth parities) are often deficient in Se and antioxidant at birth. The transfer of vitamin E and Se to colostrum and milk has also been observed to be less effective with older sows.

Stress situations have been shown to increase sulphur amino acid requirements, particularly cysteine. A recent study by Li and others, earlier this year, evaluated the effect of methionine sources (methionine, DLM or OH-methionine, HMTBA) and their dietary levels in sows during lactation on the milk quality, piglet growth and antioxidant defenses. OH-methionine treatment compared to control or DL-methionine treatments allowed higher piglet bodyweight gain during suckling and weaning periods compared to other treatments. Moreover, piglets from OH-methionine group exhibited significantly higher plasma GPx activity and plasma reduced glutathione (GSH) content and lower plasma GSSG/GSH ratio on the weaning day compared to other piglets demonstrating a better antioxidant status than other groups (seeFigure 1). This effect of the OH-methionine is explained by its better ability to be trans-sulfurated into cysteine and taurine leading to enhanced production of antioxidant compounds such as glutathione.

Organic vs inorganic

To further increase the antioxidant and immune potential of piglets, research has been done to establish the efficiency differences between organic and inorganic sources of selenium. As early as 2004, researchers Mahan and Peters showed that dietary selenium supplementation for sows with organic Se source resulted indeed in two times higher Se content in colostrum and milk of sows compared to basal diet and inorganic Se source (sodium selenite) when given from 25 kg bodyweight to their fourth parity. In addition, the Se content in tissues of neonate piglets from sows fed organic Se was higher compared to other groups. The better selenium supply through sow milk increased serum Se content of piglets at weaning.

Moreover, researchers Matte and others showed this year that prenatal transfer of inorganic Se and vitamin E from the sow to their offspring only reached 36 and 44% respectively as measured by the difference between serum concentrations in sows at the end of gestation and in piglets at birth. In addition, perinatal transfer reached 49% for inorganic Se and 210% for vitamin E respectively when comparing serum concentrations in sows at the end of gestation and in piglets at three days of age. These results confirm the low antioxidant status of piglets at birth and the necessity to improve the transfer of antioxidant from sows to their offspring, especially for Se.

Replacing inorganic Se by organic form would drastically increase transfer efficiency of the selenium from sows to their piglets. Such results show the value of the dietary antioxidant supplementation of sows during pregnancy and lactation to increase antioxidant defenses of piglets at birth that will also affect weaning antioxidant status. This concept of maternal protection is well recognised for antibodies during gestation and lactation periods passing from sows to their offspring. This concept of protection through antioxidant compounds, such as vitamin E or selenium, is getting more and more interest as they could be stored in the tissues of offspring.

Better feeding piglets

This transfer from sows to piglets and the storage of Se reserve by piglets is depending on absorption, transfer and tissue retention. In 2006, Surai reported that organic selenium is better transferred from sows to piglets and better retained by piglets in their tissues. This better retention of organic selenium compared to inorganic is mainly explained by the unspecific storage of seleno-methionine in place of methionine in body protein that can be mobilised for active seleno-protein production such as glutathione peroxidase (GPx), one of the main antioxidant enzymes. Whereas piglets that were supplemented with an antioxidant solution (vitamin, polyphenol and trace minerals such as Se) during the two weeks following the weaning, the plasma Se had the stronger negative correlation with the plasma ROS.

The selenium supplementation during the weaning or first post weaning period is also a crucial point since Se absorption is also dependent on the supplied source. A pure source of selenium, the seleno-hydroxymethionine (HMSeBA, Selisseo), appeared even 40 and 60% more efficiently incorporated in liver and muscle than Se-yeast in young piglets (Figure 2). Such efficient deposition improves Se and antioxidant status in young piglets and leads to improved antioxidant status.

Indeed, if selenomethionine represents the storage form for selenium in the body, the active form in the active seleno-proteins such as GPx is seleno-cysteine and feeding HMSeBA further increased this Se-Cys compared to seleno-methionine from Se-yeast. Based on the demonstrated enhanced trans-sulfuration of the hydroxy-methionine compared to methionine in piglets, leading to improved anti-oxidant status, the stimulation of trans-selenation would lead to higher selenoprotein formation which will further improve the antioxidant potential compared to seleno-methionine based products.

Regarding the usual concern on sanitary and clinical status of suckling and weaning piglets it appears that oxidative stress gains more and more interest as it is always increased during those periods even without visible clinical signs. Considering that point, antioxidant strategies have to be adjusted accurately in order to supply all the elements that are needed in order to sustain antioxidant systems in the critical periods such as the early stage for piglets. Improving health status and the resistance to these critical phases will not only improve the number of live piglets but also promote better growth in the following growing-finishing phases.

References available on request

[Source: Pig Progress Special – Piglet Health, 2014]

Pierre-André Geraert, Yves Mercier and Florian Couloigner

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