Soto-Navarro S A, Lawler T L, Taylor J B, Reynolds L P, Reed J J, Finley J W, Caton J S
Department of Animal and Range Sciences, North Dakota State University, Fargo 58105, USA.
J Anim Sci. 2004 Jun;82(6):1788-93. doi: 10.2527/2004.8261788x.
Twelve crossbred steers (351 +/- 24 kg initial BW) were used to determine effects of high-Se wheat on visceral tissue mass, intestinal cell growth, and intestinal cellularity and vascularity. Steers were allotted randomly by BW to one of two treatments consisting of 75% concentrate diets that supplied 1) adequate Se concentration (7 to 12 microg x kg x BW(-1) x d(-1)) or 2) high-Se concentration (60 to 70 microg x kg x BW(-1) x d(-1)). Diets were similar in composition, including 25% grass hay, 25% wheat, 39% corn, 5% desugared molasses, and 6% wheat middlings supplement on a DM basis. In the Se treatment, high-Se wheat (10 ppm Se, DM basis) was replaced with low-Se wheat (0.35 ppm Se, DM basis). Diets were formulated to be similar in CP and energy (14.0% CP, 2.12 Mcal of NEm/kg, and 1.26 Mcal NEg/kg of DM) and were offered daily (1500) to individual steers in an electronic feeding system. Diets were fed at 2.38% BW. After 126 d, steers were slaughtered, and individual visceral tissue weights determined. Concentrations of DNA, RNA, and protein of duodenum, ileum, and total small intestine were not affected (P > or = 0.33) by treatment. Similarly, RNA:DNA and protein:DNA ratios in duodenum, jejunum, ileum, and whole small intestine were not (P > or = 0.33) affected by feeding high-Se wheat. Conversely, jejunal weight was greater (P < 0.002) in steers fed high-Se wheat than in controls (916 vs. 1,427 +/- 84 g). Jejunal DNA was increased (P < 0.04) in steers fed high-Se wheat (2.95 vs. 3.56 +/- 0.19 mg/g), suggesting increased cell number. Concentrations of jejunal RNA and protein were not altered by treatment; however, because the jejunal weight increased in high-Se steers, DNA, RNA, and protein contents (grams) were greater than in control steers (P < 0.05). Vascularity of jejunal tissue decreased (P < 0.10) with high-Se wheat; however, because jejunal mass was greater for the high-Se wheat treatment, total microvascular volume was not affected by treatment. Percentage of jejunal crypt cell proliferation was not affected (P = 0.48) by treatment; however, total number of cells proliferating within the jejunum was increased in steers fed high-Se wheat. Data indicate that the lower jejunal vascularity in the diet high in Se (provided from wheat) may have resulted in increased jejunal mass to meet physiological nutrient demand. Therefore, negative effects of Se level used in this study on productive performance of feedlot steers are not expected.
选用12头杂交阉牛（初始体重351±24千克）来确定高硒小麦对内脏组织质量、肠细胞生长、肠细胞密度和血管分布的影响。根据体重将阉牛随机分配到两种处理之一，两种处理的精料日粮占比均为75%，分别提供：1）适宜的硒浓度（7至12微克/千克体重/天）；2）高硒浓度（60至70微克/千克体重/天）。日粮组成相似，以干物质计，包括25%的禾本科干草、25%的小麦、39%的玉米、5%的脱糖蜜和6%的小麦麸补充料。在硒处理组中，高硒小麦（10毫克/千克硒，干物质计）被低硒小麦（0.35毫克/千克硒，干物质计）替代。日粮的粗蛋白和能量水平相近（14.0%粗蛋白、2.12兆卡代谢能/千克、1.26兆卡维持净能/千克干物质），通过电子饲喂系统每天（15:00）单独饲喂阉牛。按体重的2.38%投喂日粮。126天后，屠宰阉牛，测定各内脏组织重量。十二指肠、回肠和整个小肠的DNA、RNA和蛋白质浓度不受处理影响（P≥0.33）。同样，十二指肠、空肠、回肠和整个小肠的RNA:DNA和蛋白质:DNA比值也不受高硒小麦饲喂的影响（P≥0.33）。相反，饲喂高硒小麦的阉牛空肠重量显著高于对照组（P<0.002）（916克对1427±84克）。饲喂高硒小麦的阉牛空肠DNA含量增加（P<0.04）（2.95毫克/克对3.56±0.19毫克/克），表明细胞数量增加。空肠RNA和蛋白质浓度不受处理影响；然而，由于高硒阉牛空肠重量增加，DNA、RNA和蛋白质含量（克）高于对照阉牛（P<0.05）。高硒小麦使空肠组织的血管分布减少（P<0.10）；然而，由于高硒小麦处理组的空肠质量更大，总微血管体积不受处理影响。空肠隐窝细胞增殖百分比不受处理影响（P=0.48）；然而，饲喂高硒小麦的阉牛空肠内增殖细胞总数增加。数据表明，高硒（来自小麦）日粮中较低的空肠血管分布可能导致空肠质量增加以满足生理营养需求。因此，本研究中使用的硒水平对育肥牛生产性能的负面影响预计不会出现。
