PARTNER FEATURE ▶▶▶
Heat stress: The positive effects of selenium
Heat stress has a dramatic impact on feed consumption and milk production in dairy cows. It is responsible for large economic losses in the livestock industry. Documented evidence has proven that selenium can effectively alleviate heat stress in dairy cows.
BY KIM WILSON, TECHNICAL COMMERCIAL MANAGER ORFFA H
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34 ▶DAIRY GLOBAL | Volume 7, No. 3, 2020
eat stress in all animals elicits a physiological re- sponse resulting in elevated internal temperature. To get back to homeostasis, dairy cows will in- crease respiration rate, panting and sweating
which leads to energy expenditure taken away from milk yield and reproductive performance. Meanwhile, dry matter (DM) intake is reduced. Animals with this status are more prone to secondary bacterial infections that can also contrib- ute to poor performance. Cows are especially at risk around parturition, specifically from week-1 to peak lactation. Strate- gies to reduce oxidative and metabolic stress associated with inflammation are necessary. Along with management solu- tions to alleviate heat stress such as installing sprinklers, add- ing an adequate source of selenium that can change the im- munological and physiological status is an option to combat heat stress. Excential Selenium 4000, a pure L-selenomethio- nine dust-free feed preparation, is a readily available form which provides the highest selenium deposition, while reduc-
Figure 1 - Selenium deposition in milk. Control
Sodium selenite Excential Selenium4000 a a b c d d bc c Selenized yeast
ing oxidative stress by decreasing free radicals and inflamma- tory response to sustain performance under stress conditions.
Selenium improving immunity status There is documented evidence that Excential Selenium 4000 (Se4000) increases the deposition of selenium in livestock in- cluding equine, swine, broilers, layers and dairy relative to both selenite and selenised yeast. As seen in Figure 1, a total of 24 Holstein Friesian cows, originally on a low Se diet, were placed on one of the four following treatments:
1. Control (no Se supplementation); 2. Sodium selenite (Control + 0.3 ppm Se from sodium selenite);
3. Selenised yeast (Control + 0.3 ppm Se from selenised yeast);
4. Excential Selenium 4000 (Control + 0.3 ppm Se from Excential Selenium 4000).
The inclusion of Se4000 resulted in the highest deposition in milk: 61% increase relative to selenite and outperforming se- lenised yeast. This also translates to improved Se deposition in colostrum, which can lead to improved passive immunity. This is because L-selenomethionine can be stored in the body in replacement of methionine. As a result, selenium in the form of L-selenomethionine is incorporated and stored in muscle, milk and blood and can be mobilized via selenide to de novo selenocysteine in the liver and subsequent enable selenoprotein synthesis when required. Although selenised yeast has some L-selenomethionine and other organic seleni- um derivatives, those other derivates cannot be incorporated into animal proteins the same way; less selenomethionine means less deposition and storage reserves. The more readily available L-selenomethionine (Se4000) al- lows for improved immune status. In mammals, it was discov- ered that providing L-selenomethionine significantly lowered expression of Cyclooxygenase-2 (Cox2) and interferon gam- ma (Ifnγ) relative to selenite, and numerically lower relative to selenised yeast, during normal production. These genes are involved in inflammation when elevated. In the same study during a pathogen (lipopolysaccharide) challenge, mammals that were given selenite as their selenium source had a gene profile that indicated oxidative stress (elevated up-regulation of Txnrd1, Cat, selenogenes SelS and SelN1
Se in milk, μg/kg
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