The Biological Basis for Selenium Requirements of Animals

Comparison of Selenium Source in Preventing Oxidative Stress in Bovine Mammary Epithelial Cells

Oxidative stress can cause cell damage. Hydroxy-selenomethionine (HMSeBA) is an organic Se source with emerging antioxidant advantages. The objective of this study was to compare the effects of HMSeBA, selenomethionine (SeMet) and sodium selenite (SS) on the antioxidant response and the ability to resist oxidative stress in bovine mammary epithelial cells (BMEC). The BMEC were treated with 0 (Control), 20, 50, 100 and 150 nM HMSeBA, 100 nM SeMet and100 nM SS for 48 h. The results showed that HMSeBA and SeMet treatments had higher glutathione peroxidase (p < 0.01) and catalase (p = 0.01) activities and mRNA abundance of GPX3 (p = 0.02), but lower superoxide dismutase activity compared with SS (p = 0.04). The catalase activity (p < 0.05) and mRNA abundance of GPX3 (p = 0.04) changed in a quadratic manner with the increase of HMSeBA levels. To assess the potential protection of different Se sources against oxidative stress on BMEC, 0 or 50 μM H2O2 was added to BMEC culture for 3 h after Se pre-treatment for 48 h. The results showed that HMSeBA and SeMet, which did not differ (p > 0.05), but further decreased malondialdehyde and reactive oxygen species production compared with SS (p < 0.05). In conclusion, HMSeBA showed an enhanced cellular antioxidant status to resist oxidative damage induced by H2O2 when compared with SS, whereas the effects were similar to SeMet.

Comparison of trace mineral repletion strategies in feedlot steers to overcome diets containing high concentrations of sulfur and molybdenum

To compare trace mineral (TM) repletion in feedlot steers after depletion by S and Mo, 72 Red Angus steers blocked by BW (253 ± 14 kg) were assigned (6 steers per pen, fed via GrowSafe bunks) to corn silage depletion diets (depletion, DEP) supplemented with NRC (1996) recommended concentrations of Cu, Mn, Se, and Zn (CON) or supplemented with 0.3% S (CaSO4), 2 mg of Mo/kg dry matter (DM), and no added Cu, Mn, Zn, or Se (antagonist, ANT). Three 62 d TM repletion strategies (repletion, REP) were applied within DEP diets on day 89: 1) Multimin90 injection (contains Cu, Mn, Se, Zn) and 100% of recommended Cu, Mn, Zn, and Se from inorganic sources (ITM), 2) saline injection and 150% of recommended TM from inorganic sources (ING), or 3) saline injection and 150% of recommended TM provided as 25% organic and 75% inorganic sources (BLEND). Subcutaneous injections were given at 1 mL/68 kg BW. Inorganic sources were Cu, Mn, and Zn SO4, and sodium selenite, and organic sources were Availa Cu, Mn and Zn, and SelPlex Se. Repletion period liver and blood were collected on day -10, 14, 28, and 42 and data were analyzed as a 2 × 3 factorial (n = 12 steers per treatment) using Proc Glimmix of SAS with plasma and liver analytes analyzed as repeated measures. Liver Cu, Se, and Mn were decreased (P < 0.01) by ANT during DEP. There were no DEP × REP × day interactions in liver TM (P ≥ 0.18). A DEP × day effect was noted for liver Cu (P < 0.01) and Mn (P = 0.07), where ANT Cu increased linearly from day 0 to day 42, CON Cu was slightly increased on day 14 and day 28, and ANT Mn was lesser than CON Mn on all days except day 42. There were REP × day effects on liver Cu (P < 0.01) and Se (P < 0.01) where status was improved by ITM by day 14, increased in BLEND by day 28, and not different by day 42. Liver Se concentrations were lesser (P < 0.01) in ANT vs. CON throughout repletion. Liver Zn was greater (P < 0.01) on day 0 than day 14, 28, and 42, and concentrations were greater on day 42 than day 28. Glutathione peroxidase activity tended to be lesser (P = 0.07) on day 14 relative to other days. Manganese superoxide dismutase activity was lesser (P < 0.01) on day 14 and 28 compared to day 0 and 42, and tended to be lesser (P = 0.06) in ANT than CON during repletion. Final body weight (BW) and average daily gain (ADG) were not affected by treatment (P ≥ 0.60), and ANT decreased dry matter intake (DMI) (P = 0.04) and improved G:F (P < 0.01) during repletion. All repletion strategies were effective at increasing TM status of steers, and ITM had the most rapid recovery of Cu and Se status, followed by BLEND, and ING.

Effects of a multielement trace mineral injection and vitamin E supplementation on performance, carcass characteristics, and color stability of strip steaks from feedlot heifers

The objective was to evaluate the interaction of a trace mineral (TM) injection (Multimin 90) and a supranutritional concentration of dietary vitamin E (VITE) on performance, carcass characteristics, and color stability of strip steaks from feedlot heifers. Prior to trial initiation, Angus × Simmental cross heifers (N = 48) were managed on a common diet supplemented to meet the NRC recommendations. Heifers were stratified by BW and allotted to a 2 × 2 factorial arrangement: 1) no supplemental vitamin E and saline injection (CONT + SAL), 2) 1,000 IU vitamin E·heifer-1·d-1 and saline injection (VITE + SAL), 3) no supplemental vitamin E and TM injection (CONT + MM), or 4) vitamin E and TM injection (VITE + MM). Trace mineral injection contained 15, 10, 5, and 60 mg/mL of Cu, Mn, Se, and Zn, respectively, and TM injection or saline injection (1 mL/68 kg BW) were given on day 0 of the 89-d finishing period. All heifers were fed a common diet containing a basal concentration of 19.8 IU/kg DM vitamin E. Heifers were slaughtered and loins sections were collected. Strip steaks were cut and placed in overwrap trays for evaluation of color stability for 16 d. Data were analyzed using the MIXED procedure of SAS. Color stability data were analyzed as repeated measures. Neither TM injection nor VITE had an effect on final BW, DMI, or G:F (P ≥ 0.12). There was a tendency (P = 0.09) for TM injection to increase ADG. A tendency (P = 0.08) was observed for TM injection to increase DMI of heifers receiving supranutritional VITE. Trace mineral injection and VITE had no effect on HCW, yield grade, 12th-rib backfat thickness, or ribeye area (P ≥ 0.34). Marbling scores tended to increase (P = 0.08) in VITE heifers compared with control-fed heifers. Vitamin E supplementation decreased final lipid oxidation (1.00 vs. 1.97 µg malondialdehyde/g fat, P = 0.03) and total visual discoloration (15.82% vs. 33.96%, P = 0.04) of steaks compared with steaks from nonsupplemented heifers. Heifers fed supranutritional VITE produced steaks that maintained retail color longer shown by lower hue angle values (38.17° vs. 38.66°, P < 0.01) than nonsupplemented heifers. A TM injection × vitamin E × day interaction (P < 0.01) revealed by day 16 steaks from the CONT + MM heifers exhibited greater discoloration than VITE + SAL and VITE + MM steaks with CONT + SAL intermediate. Overall, VITE improved color stability and TM injection appeared to increase discoloration of strip steaks from feedlot heifers after day 14 of display.

Selenomethionine increases proliferation and reduces apoptosis in bovine mammary epithelial cells under oxidative stress

The decline in mammary epithelial cell number as lactation progresses may be due, in part, to oxidative stress. Selenium is an integral component of several antioxidant enzymes. The present study was conducted to examine the effect of oxidative stress and selenomethionine (SeMet) on morphology, viability, apoptosis, and proliferation of bovine mammary epithelial cells (BMEC) in primary culture. Cells were isolated from mammary glands of lactating dairy cows and grown for 3 d in a low-serum gel system containing lactogenic hormones and 0 or 100 μM H2O2 with 0, 10, 20, or 50 nM SeMet. Hydrogen peroxide stress increased intracellular H2O2 to 3 times control concentrations and induced a loss of cuboidal morphology, cell-cell contact, and viability of BMEC by 25%. Apoptotic cell number more than doubled during oxidative stress, but proliferating cell number was not affected. Supplementation with SeMet increased glutathione peroxidase activity 2-fold and restored intracellular H2O2 to control levels with a concomitant return of morphology and viability to normal. Apoptotic BMEC number was decreased 76% below control levels by SeMet and proliferating cell number was increased 4.2-fold. These findings suggest that SeMet modulated apoptosis and proliferation independently of a selenoprotein-mediated reduction of H2O2. In conclusion, SeMet supplementation protects BMEC from H2O2-induced apoptosis and increased proliferation and cell viability under conditions of oxidative stress.

Effect of anionic salts on selenium metabolism in nonlactating, pregnant dairy cows

The objective of this trial was to determine whether anionic salts in the diets of nonlactating, pregnant cows for 14 to 21 d prepartum affected measures of Se status. One of three dietary treatments (control, anionic salts, and anionic salts plus Se) was administered to 34 nonlactating, pregnant cows using a completely randomized design with repeated measures. The anionic salts were delivered via gelatin capsules that were administered orally in two equal amounts per day, and the Se (3 mg/d) was administered via an intraruminal bolus. The incidence of milk fever among cows was not significantly different across dietary treatments. The severity of hypocalcemia as indicated by concentrations of ionized Ca in serum collected < 2 h postpartum was significantly lessened by dietary anionic salts. Supplementation of anionic salts to the diet did not significantly affect serum Ca concentrations at either 7 d prepartum or 7 d postpartum. Anionic salts did not affect concentrations of Se in blood; however, Se supplementation of the diets of cows significantly increased postpartum concentrations of Se in serum. No treatment effects were detected for concentrations of Se in either serum or whole blood of newborn calves. In conclusion, these data indicate that diets supplemented with anionic salts for 14 to 21 d prepartum and the supplementation of diets with Se had independent effects on concentrations of minerals in blood. Thus, anionic salts administered to prevent milk fever without danger of significantly reducing the transfer of Se from the dam to the calf and without compromising the Se status of the cow when the anionic salts are limited to administration for 14 to 21 d before calving.