Oregon livestock producers will be interested in a new report summarizing the role of selenium in the livestock diet. The report, prepared by Fara A. Brummer, area Extension specialist/ livestock systems, North Dakota State University (formerly of Oregon State University); Gene J. Pirelli, regional Extension livestock/ forage specialist, and Jean A. Hall, professor, College of Veterinary Medicine; both of Oregon State University, discusses selenium supplementation rates, provides information on forms of Selenium and methods of supplementation and summarize selenium research conducted by Oregon State University extension.
Over the past few years, the Oregon Sheep Commission was pleased to contribute to these research efforts. To read the full report: https://catalog.extension.oregonstate.edu/files/project/pdf/em9094.pdf
GENERAL PROTOCOL OF EVENTS: The U.S. Sheep Experiment Station research and developed a selenium test product, abbreviated SePR, which was successfully tested at 3 locations; a forth location agreed to test the product, but never confirmed using the product nor collected the required test samples. Locations A and B were typical shed-lambing systems, while Location C was a pasture lambing system. With generous assistance from Intermountain Farmers Association (Salt Lake City, UT), the U.S. Sheep Experiment Station manufactured SePR using a natural selenium-rich, high-protein forage as the main ingredient. The product was pelleted and contained 16% crude protein, 67% total digestible nutrients, and 6 ppm selenium (dry matter basis). SePR was fed for 22, 20, and 40 days at Locations A, B, and C, respectively.
RESULTS: SePR enhanced the selenium status of ewes and their nursing young. Selenium content of whole blood in ewes increased 21%, 18%, and 52% for Locations A, B, and C, respectively (see Figure 1). Note that the increase was greatest for Location C, which is an effect of feeding SePR twice as long as was fed at other locations. This response is consent with the responses that were observed in a “laboratory” setting at the U.S. Sheep Experiment Station.
Selenium content of whole blood in lambs nursing the test ewes increased 25%, and 117% for Locations B and C, respectively (see Figure 2). Whole blood samples were not collected from lambs at Location A. As with the ewes, duration of feeding SePR to lactating ewes had a notable effect on whole blood selenium in ewes, with lambs from Location C having the greatest response. Note that lambs did not consume SePR and, thus, received the benefit of the product through the ewes’ milk. This response is consent with our previous results, and further demonstrates that the best time to enhance selenium status of lambs is to feed SePR to the ewes during early lactation when milk accounts for >90% of the daily nutrition of lambs.
Selenium content of wool significantly increased at all locations after SePR was fed to the ewes. Plotted in Figure 3 are the responses from Location B. I arranged the chart to compare the responses of the ewes with their offspring. First, note that the response was similar between ewes and their offspring, which demonstrates that the advantage of feeding SePR during lactation. Second, note that the magnitude of response in wool is much greater than what was observed in whole blood (Figures 1 and 2). This demonstrates that selenium from SePR readily enriches the body’s general protein pool with selenium. Many have asked why I focus on wool so much. Based on results from recent work, enrichment of wool with selenium is similar to what we observed in skeletal muscle when SePR-like products were fed to sheep. Unlike a muscle biopsy, wool is easy to collect and doesn’t cause any harm to the animal. Therefore, when I see a doubling of wool selenium, I expect the same response in the muscle. This is where products that are high in selenomethionine, like SePR, really “shine.” Selenium that is incorporated in the muscle tissue can act as a “selenium reserve,” which slowly releases selenium back to the body over long periods of time; an effect not possible with sodium selenite.
IMPLICATIONS: These data demonstrated that what we had observed in a “laboratory” setting is repeatable on the farm; feedstuffs that are naturally rich in selenium can be used in a short-term feeding program to rapidly enhance the selenium status of ewes and their nursing young. The potential enrichment of skeletal muscle with selenium, as estimated by wool results, will have a long and lasting effect well after feeding SePR on the selenium status of the ewes and lambs. In other words, a short-term feeding effort to achieve a long-term positive effect.
CONTINUATION: A second trial year was initiated spring 2013. Two locations agreed to test the product. Final samples will be collected in August. Analyses will be completed in October.