Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Abstract only
Publication Acceptance Date: 12/1/2003
Publication Date: 12/10/2003
Citation: Soto-Navarro, S.A., Williams, G.J., Taylor, J.B., Finley, J.W., Caton, J.S.2003. Effects of selenium source of characteristics of selenium digestibility in finishing beef steers [abstract]. Journal of Animal Science. 81(Suppl.2):95. Interpretive Summary: The objective of this study was to determine the effects of selenium source (high Se wheat, high Se alfalfa/grass hay, or sodium selenate) on selenium digestibility. Four ruminally and duodenally cannulated steers were utilized. Total fecal output collected and measured with fecal bags for five days. Duodenal samples collected twice daily for four days. When selenium was provided at supranutritional levels, organic sources of selenium increased incorporation of selenium into ruminal bacteria and increased total tract selenium disappearance.
Technical Abstract: Four ruminally and duodenally cannulated steers (604 ± 9.26 kg initial BW) were used in a 4 x 4 Latin square to evaluate effects of Se source on characteristics of Se digestibility. Steers were offered feed ad libitum at 0700 and 1900 daily and were allowed free access to water. The basal diet contained (DM basis) 25% grass hay, 25% wheat, 39% corn, 6% desugared molasses, and 5% wheat middling-based supplement. Treatments were: 1) Se adequate (CON; 0.38 ppm), or Se provided as high Se wheat (WHT; 2.86 ppm Se), high Se hay (HAY; 2.80 ppm Se) or sodium selenate (SEO; 2.84 ppm Se). Diets were formulated to supply 65 ug·kg-1 BW (WHT, HAY, and SEO), and 9.5 ug·kg-1 BW (CON) of Se, and were similar in N and energy content (14% CP, 2.12 Mcal NEm·kg-1 DM, and 1.26 Mcal NEg·kg-1 DM). Wheat and hay in CON were replaced with high-Se wheat and hay in WHT and HAY (10.26 and 10.17 ppm Se, respectively). Experimental periods consisted of 9-d diet adjustment followed by 5-d collection. During collections, fecal output was measured using fecal bags, duodenal samples were taken twice daily from all steers as follows: d2, 0630 and 1230; d3, 0800 and 1400; d4, 0930 and 1530; and d5, 1100 and 1700. Dry matter intake, OM intake, and total tract OM digestibility were not affected (P > 0.10) by treatment. Analyzed dietary Se was 0.42, 3.0, 5.47, and 3.15 ppm for CON, WHT, HAY, and SEO respectively. Selenium flow to the duodenum was CON < WHT = SEO < HAY (P < 0.01; 3.9, 23.2, 28.2, 39.5 ± 3.27 mg/d, respectively). However, when expressed as % of Se intake, Se flow to duodenum was not affected (P > 0.10) by treatment. Microbial Se reaching the duodenum was lower (P < 0.01) for CON and SEO compared with WHT and HAY (2.4, 6.1, 10.9, 15.5 ± 1.81 mg/d, respectively). When expressing microbial Se flow as % of Se intake, CON > WHT = HAY = SEO, and WHT > SEO (P <0.01); 59.9, 36.7, 27.6, and 21.2 ± 5.6 %, for CON, WHT, HAY and SEO, respectively). Total tract Se digestibility of CON was lower then WHT and HAY (P = 0.07), and SEO was similar to CON, WHT, and HAY. No effects (P > 0.10) on apparent ruminal, true ruminal, or postruminal Se disappearance were noted. When providing Se at supranutritional levels, organic sources of Se increased incorporation of Se into ruminal bacteria and increased total tract Se disappearance.