Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2005
Publication Date: 1/30/2005
Citation: Taylor, J.B. 2005. Time-dependent influence of supranutritional organically bound selenium accumlation in growing wether lambs. Journal of Animal Science. 83:1186-1193. Interpretive Summary: Opportunities to supplement selenium to grazing sheep are sometimes limited in extensive North America range sheep operations. Feeding growing wethers 2.9 ug selenium/g dry matter, as high selenium wheat grain, increases the amount of selenium deposited in the body within 14 days, and enhances skeletal muscle selenium six-fold within 56 days. The strategic use of high selenium wheat grain to deliver supranutritional selenium levels, provides a readily available source of selenomethionine, and rapidly increases tissue selenium levels in wether lambs without adversely influencing performance. Such a selenium supplementation strategy could provide sheep with an endogenous selenium source during periods of inadequate selenium intake, and increase the selenium content of retail skeletal muscle products.
Technical Abstract: Crossbred wethers (n = 36; BW = 36.0 kg; SD = 3.4) were used to assess the time dependent influence of supranutritional Se, provided as high Se wheat grain, on Se accumulation. Four wethers were slaughtered before trial commencement (d 0). The remaining wethers were fed diets containing adequate (0.2 ug Se/g DM) or supranutritional Se (2.9 ug Se/g DM), in the form of high Se wheat grain, for 14, 28, 42, or 56 d before slaughter (n = 4/Se treatment/slaughter day). The DMI set at 3.1% of BW and adjusted weekly based on a targeted ADG of 150 g. Daily Se intake of wethers fed the adequate and supranutritional Se diets ranged from 5.3 to 5.9, and 79.0 to 95.0 ug Se/kg BW, respectively, and within Se treatment, did not differ (P = 0.84 to P = 0.99) between slaughter day groups. Neither Se treatment nor Se treatment x slaughter day interactions were significant for BW, G:F, or liver, kidneys, and spleen weights (P = 0.06 to P = 0.84). Within the supranutritional Se treatment, Se contents of most organs and tissues were nearly twice the concentrations (P < 0.01) of wethers slaughtered on d 14, 28, 42, and 56 relative to wethers slaughtered on d 0. When regressed against days fed supranutritional Se, Se concentrations increased (P < 0.001) cubically in kidneys and plasma, quadratically in duodenum, lung, liver, and spleen, and linearly in heart, muscle, and wool. For total Se in kidneys, liver, and spleen, the response was quadratic (P < 0.03). Excluding skeletal muscle, heart, and wool, Se in other organs and tissues reached apparent steady state concentrations 14 to 28 d after commencement of supranutritional Se diets. Selenium concentrations in skeletal muscle accumulated in a linear manner (P < 0.001) throughout the 56-d feeding period indicating that skeletal muscle Se was not nearing steady state. High Se grains can be used strategically to deliver supranutritional Se and rapidly enhance Se depots in sheep in a very short time, a task that does not seem accomplishable with Se salts. Furthermore, a 100-g portion of uncooked loin (longissimus dorsi) from the wethers fed supranutritional Se contains 196 to 250% of the recommended Se requirement for humans.