Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 5, 2003
Publication Date: June 6, 2003
Citation: Lawler, T.L., Taylor, J.B., Finley, J.W., Caton, J.S. Effect of feeds naturally high in selenium on performance and selenium concentration in various tissues of finishing beef steer. Journal of Animal Science. 2003. v. 81 (Suppl.1) Abstract p. 80. Interpretive Summary: Beef is a major source of selenium in the diet of North Americans. Previous research has revealed that the concentration and form of selenium in the diet of an animal will affect the amount of selenium deposited in tissues such as liver, spleen and skeletal muscle. This project focused not only on assessing the effects of feeding high levels of selenium to finishing beef steers, but also compared feeds naturally high in selenium (wheat grain and alfalfa-grass mix hay; feeds were obtained from geographic regions soil selenium is high and readily available to plants) to the traditional form of selenium used in supplements, inorganic selenium salts. At the end of the 126 day finishing trial, selenium concentration in skeletal muscle, kidney, liver (only for wheat grain) and spleen was found to be greatest for steers consuming higher amounts of selenium provided by feeds naturally high in selenium. These results reveal: 1) an effective method to produce a beef product that is naturally high in selenium, and 2) a potential market for feeds (grains, hay) naturally high selenium through the provision of a readily available selenium source to cattle.
Technical Abstract: The majority of the human daily requirement of selenium (Se), a key component of prooxidant defense mechanisms, can be obtained from beef. Although Se content of edible beef tissue is highly variable, previous research suggests that the Se content these tissues can be influenced by the concentration and molecular form of Se in feedstuffs consumed. For example, cattle grazing geographical regions where naturally occurring Se in forages is high have a greater tissue Se content compared to beef from regions of lower Se. However, data are limiting that describe effects of feeds naturally high in Se on the performance and tissue Se concentration of finishing beef steers. Forty-five beef steers (BW = 351.1 ± 24.1 kg) were assigned to one of four finishing dietary treatments: Se adequate (CON; n = 12), or high Se provided as high Se wheat (WHT; n = 11), high Se hay (HAY; n = 11), or sodium selenate (SEO; n = 11). Selenium content for WHT, HAY, and SEO diets was 65 µg·kg-1 BW·d-1, and for CON, 9.5 µg·kg-1 BW·d-1. The diets were individually offered once daily for 126 d. Treatment did not affect (P > 0.1) intake, feed efficiency, average daily gain, hot carcass weight, longissimus muscle area, back fat thickness, marbling score, or quality and yield grade of the steers. Kidney, pelvic, and heart fat was higher (P = 0.06) among CON and WHT compared to SEO and HAY (2.9, 2.9, 2.4, 2.5 ± 0.2%, respectively). Concentration of Se in kidney and spleen was different (P < 0.01) in response to treatment with WHT > HAY > SEO > CON (12.98, 10.86, 10.05, 8.40 ± 0.26 ppm for kidney and 5.16, 3.82, 2.60, 2.00 ± 0.09 ppm for spleen; respectively). Liver samples contained 10.79, 6.56, 9.91, 2.33 ± 0.80 ppm Se for WHT, HAY, SEO, and CON, respectively, where WHT = SEO > HAY > CON (P < 0.01). Selenium content of the semitendinosus muscle was much greater (P < 0.01) in treatments containing feeds naturally high in Se (WHT > HAY > SEO = CON; 4.41, 3.32, 1.55, 1.33 ± 0.18 ppm, respectively). In conclusion, producers can effectively increase selenium concentration in muscle tissues by feeding feedstuffs naturally high in Se (e.g., wheat, hay) without compromising performance or carcass characteristics. These results reveal: 1) a potential market for feeds (grains, hay) naturally high Se through the provision of a readily available Se source to cattle, and 2) an effective method to create a beef product that is naturally high in Se.