Organic Se Sources Research Articles

Efficacy of Se-enriched Alga Chlorella spp. and Se-enriched Yeast on Tissue Selenium Retention and Carcass Characteristics in Finisher Pigs

The aim of this study was to evaluate the effect of organic Se from Se-enriched alga (Chlorella spp.) and Se from Se-enriched yeast on concentrations of Se in serum and tissues, and serum GSH-Px activities and carcass characteristics in finishing pigs. The pigs were on experimental diets for a period of 3 months before slaughter with different Se supplements at the concentration of 0.3 mg Se per kg of feed. In group I (n = 12) the feed was supplemented with inorganic sodium selenite; in group II (n = 12) with organic Se from Se-enriched yeast; in group III (n = 12) with organic Se from Se-enriched alga, Chlorella spp. and pigs in group IV (n = 11) received a non-supplemented basal diet. The organic Se sources did not differ in serum Se and serum GSH-Px activities. Significantly higher Se concentrations in muscle (P < 0.01) and in the heart (P < 0.01) were found when Se from Se-enriched yeast was given, compared to the group of pigs that received Se from Se-enriched alga Chlorella spp. The Se content in livers and ovaries did not differ between the two organic Se sources. The use of both organic Se forms resulted in a higher accumulation in muscle tissue compared to the inorganic Se form. No differences in meat quality characteristics were found among the experimental groups. It is concluded that Se from Se-enriched alga, Chlorella spp. had a lower accumulation in muscle tissue than Se from Se-enriched yeast, and it did not affect meat quality.

Comparison of Selenium Levels and Sources and Dietary Fat Quality in Diets for Broiler Breeders and Layer Hens

Two experiments were carried out with broiler breeders (experiment 1) and laying hens (experiment 2) to study the effects of Se sources, in interaction with dietary level of Se or dietary fats on performance, Se incorporation into tissues (blood, liver, breast muscle, and egg) and eggs, hatchability, and glutathione peroxidase (GPX) activities in tissues and blood. Both experiments involved a 3 x 2 factorial arrangement of 3 Se sources (selenite, Se yeast, or B-Traxim Se) and either 2 levels of each source (0.1 or 0.3 mg/kg) or 2 fats (fresh or oxidized). Egg production was not affected by Se source or dietary fat in both experiments. Egg production was greater (P < 0.01) in breeder hens fed 0.3 mg/kg of Se in experiment 1. Hatchability of eggs from hens fed 0.1 mg/kg of Se was lower (P < 0.05) in hens fed Se yeast, whereas from hens fed 0.3 mg/kg of Se, it was comparable across treatments. Selenium in egg, liver, and breast muscle was greater (P < 0.01 or <0.05) in hens fed the greater concentration of Se. Eggs from breeder hens fed organic Se sources had greater (P < 0.01) Se content than those of inorganic source. Egg albumen from breeder fed Se yeast had the greatest Se (P < 0.01), whereas egg yolk from hens fed B-Traxim Se had the greatest Se (P < 0.05). These parameters were affected by interaction between dietary Se level and source (P < 0.01 or < 0.05). Selenium contents in liver and breast muscle were greater (P < 0.01) in hens fed Se yeast compared with hens fed other sources of Se. In experiment 1, liver GPX was greater (P < 0.01) in hens fed selenite or Se yeast, whereas plasma GPX was greater (P < 0.01) in hens fed selenite compared with B-Traxim Se or Se yeast. Supplementation with oxidized fat increased (P < 0.05) GPX in blood and liver. B-Traxim Se decreased (P < 0.05) malondialdehyde content in breast muscle of layers. It is concluded that broiler breeders require supplementation of 0.3 mg/kg of Se, and that there are numerous measurable advantages in using organic rather than inorganic sources for both breeders and layers.

Dietary selenium increases vitamin E contents of egg yolk and chicken meat

1. The influence of different forms of dietary selenium (Se) on vitamin E (α-tocopherol) and Se contents of egg yolk and chicken meat was investigated. 2. Eggs were collected from laying hens subjected to 4 different dietary treatments after 24 weeks of age. Treatments compared the effects of inorganic Se supplementation (selenite) to those of organic (Se-enriched yeast, Se-enriched alga Chlorella) supplements. In a second experiment the effect of the above organic dietary Se supplementation on the α-tocopherol contents of meat from broiler chickens was evaluated. 3. Dietary Se supplementation increased the α-tocopherol content of egg yolks from 297 mg/kg dry matter in treatment without supplementation to 311 mg/kg when selenium was supplemented as selenite, and to 370–375 mg/kg when organic supplements were used. The Se and α-tocopherol contents of breast and thigh meat in broilers were significantly increased by organic dietary Se supplementation. 4. The inclusion of organic dietary Se sources in the diets of laying hens and broilers would enhance the nutritional value (vitamin E and Se contents) of products (eggs and meat) for human consumption.

Effects of different selenium sources on tissue selenium concentrations, blood GSH-Px activities and plasma interleukin levels in finishing lambs

Thirty-two wether lambs of Tan sheep were randomly assigned into four dietary treatment groups (eight per group) for an 8-wk study and then fed a basal diet deficient in Se (0.06 mg/kg) or diets supplemented to provide 0.10 mg/kg Se from sodium selenite, selenized yeast, and seleniumenriched probiotics, respectively. Blood samples were collected at d 0, 28, and 56 of the experiment and tissue samples were collected at experiment termination. Tissue and blood Se concentrations, blood glutathione peroxidase (GSH-Px) activities, and plasma interleukin levels were analyzed. The results showed that the concentrations of Se in the kidney, liver, and muscle increased in all of the supplemented groups (p < 0.01) compared with the control group. However, the Se concentrations in the kidney, liver, and muscle in the groups supplemented with Se yeast and Se-enriched probiotics were higher than those in the group supplemented with sodium selenite (p < 0.01). The activities of GSH-Px and the concentrations of Se in blood also increased in all of the supplemented groups during the period of supplementation (p < 0.01) compared with the control group. The activities of GSH-Px and the concentrations of Se in the whole blood of the lambs fed with selenized yeast and Se-enriched probiotics were higher than those of lambs fed with sodium selenite (p<0.01 or p<0.05). The concentrations of interleukin-1 and interleukin-2 in plasma significantly increased in all of the supplemented groups during the entire period of experiment (p<0.01) compared with the control group, but had no significant differences among all of the supplemented groups. In conclusion, a diet supplemented with Se for finishing lambs was able to increase the concentrations of Se in tissue and blood, activities of GSH-Px in blood, and levels of interleukins in plasma. Organic Se sources (selenized yeast and Se-enriched probiotics) were more effective than the inorganic Se source (sodium selenite) in increasing tissue and blood Se concentrations and blood GSH-Px activities of lambs. However, there were no significant differences in plasma interleukin levels of lambs between organic and inorganic Se sources.

Effect of Source and Concentration of Selenium on Growth Performance and Selenium Retention in Broiler Chickens

A 6-wk experiment was conducted using 360 one-day-old Jumbo Cornish Cross broiler chicks to evaluate the effects of the source and concentration of Se on growth performance and Se retention. Broilers were fed corn-soy-based diets formulated to contain 0 (negative control), 0.1, 0.2, or 0.3 ppm of supplemental Se from SelenoSource AF (Se yeast A, Diamond V Mills, Cedar Rapids, IA), 0.3 ppm of Se from Sel-Plex (Se yeast B, Alltech, Nicholasville, KY), or 0.3 ppm of Se from sodium selenite. Starter diets were fed for the first 21 d (6 replicates of 10 broilers per treatment). On d 21, broilers were regrouped within dietary treatments to finisher cages (11 replicates of 5 broilers per treatment) and fed finisher diets for the following 21 d. Feed intake was measured daily. Body weights of the broilers were measured on d 1, 21, and 42. Excreta samples were collected for 4 consecutive days at the end of each 3-wk feeding period to estimate Se retention. Blood samples were collected from 11 broilers per treatment on d 42 to determine blood Se concentrations and glutathione peroxidase (GPX) activity. Selenium supplementation did not influence (P > 0.05) the growth performance of broilers at 42 d of age. Blood Se and GPX activities increased (P < 0.05) as the concentration of Se in diets increased. Selenium retention as a percentage of Se intake decreased linearly (P = 0.01) as the concentration of Se increased in the diets. At 0.3 ppm, blood Se and GPX activities were higher (P = 0.01) for broilers supplemented with Se yeast A compared with Se yeast B when expressed as relative to Se intake. Selenium retention was greater when organic Se was supplemented (P = 0.01), compared with inorganic Se. Results of the study suggest that Se retention had an inverse relationship with the concentration of Se supplemented and was influenced by the dietary source of Se. Whole blood Se relative to Se intake suggests a higher bioavailability of Se from the organic source compared with inorganic sodium selenite and that differences in bioavailability may exist between organic sources of Se.

Efficacy of dietary selenium sources on growth and carcass characteristics of growing-finishing pigs fed diets containing high endogenous selenium

A study was conducted to determine the efficacy of organic (Se-yeast, SelenoSource AF, Diamond V Mills Inc., Cedar Rapids, IA) and inorganic sources of Se on growth performance, tissue Se accretion, and carcass characteristics of growing-finishing pigs fed diets with high endogenous Se content. A total of 180 pigs at 34.4 +/- 0.06 kg of BW were allotted to 1 of 5 dietary treatments: a negative control without added Se (NC); 3 treatment diets with 0.1, 0.2, or 0.3 mg/kg of added Se from an organic source; and a diet with 0.3 mg/kg of added Se as sodium selenite. Each treatment had 6 pens, with 6 pigs per pen-replicate. Experimental diets were changed twice at 66.1 +/- 0.5 kg and 99.0 +/- 0.9 kg of BW, and were fed until the pigs reached market weight. Growth performance was measured at the end of each phase. Upon reaching 129.9 +/- 1.4 kg of BW, the pigs were transported to a local abattoir (Seaboard Foods, Guymon, OK), where carcass, loin, and liver samples were obtained. Hair and blood samples were obtained at the beginning and end of the study for Se analysis. Growth performance did not differ (P > 0.05) among treatments. Percent drip loss of the NC pigs was greater (2.41 vs. 1.75, P = 0.011) compared with pigs supplemented with Se. Pigs fed diets with added Se had greater Se concentrations in the liver (0.397 vs. 0.323 ppm, P = 0.015), loin (0.236 vs. 0.132 ppm, P < 0.001), serum (0.087 vs. 0.062 ppm, P = 0.047), and hair (0.377 vs. 0.247 ppm, P = 0.003) compared with the NC pigs. Percentage drip loss was linearly reduced [percent drip loss = 2.305 - (2.398 x Se), r2 = 0.29, P = 0.007] as dietary organic Se concentration increased. The Se concentration (ppm) in the liver [liver Se = 0.323 + (0.291 x Se), r2 = 0.33, P = 0.003], loin [loin Se = 0.122 + (0.511 x Se), r2 = 0.57, P < 0.001], serum [serum Se = 0.060 + (0.113 x Se), r2 = 0.33, P = 0.004] and hair [hair Se = 0.237 + (0.638 x Se), r2 = 0.56, P < 0.001] increased linearly as dietary organic Se concentration increased. Slope ratio analysis indicated that the relative bioavailability of organic Se for percent drip loss and loin and hair Se response was 306, 192, and 197% of that for inorganic Se, respectively. The results of the study show a potential advantage of organic Se supplementation in reducing drip loss even when the basal diet contains an endogenously high Se concentration of 0.181 ppm.

Effect of Selenium Source and Level in Hen's Diet on Tissue Selenium Deposition and Egg Selenium Concentrations

The present study was conducted in a 2 x 4 factorial arrangement in a randomized complete block (RCB) design to compare the effects of a commercial inorganic Se source (sodium selenite, SS) with a commercial organic Se source (Se-enriched yeast, SY) on tissue Se distribution and blood and whole-egg Se concentrations in laying hens. Both Se sources were added into the basal diet at 0, 0.2, 0.5, and 1.0 mg/kg of Se. Seven hundred 68 week old Rohman laying hens were fed with a basal diet containing 0.15 mg/kg DM (dry matter) of Se for 2 weeks, and then, they were allocated randomly into seven groups and were investigated for 28 days. Each group was replicated five times with five cages of four hens per cage in each replicate. During the experiment, two eggs per replicate from each treatment were collected every 7 days and blood was sampled on days 0, 14, and 28 for whole-egg and whole-blood Se analyses. At the end of the experiment, two hens per replicate from each treatment were slaughtered, and muscle (cardiac and breast muscles), liver, spleen, and kidney were sampled for the determination of Se concentrations. The results showed that the addition of Se from either source caused a significant increase in whole-egg and whole-blood Se concentrations (p < 0.01) and Se concentrations in liver, kidney, spleen, and cardiac and breast muscles (p < 0.05) of hens in comparison to the control. Both Se sources and Se levels significantly influenced (p < 0.01) Se concentrations in egg, blood, and the above-mentioned tissues. There was a more significant increase in the Se concentrations in egg (p < 0.01), spleen (p < 0.05), and breast muscle (p < 0.01) and a decrease (p < 0.01) in whole-blood and kidney from hens fed SY than those from hens fed SS. The order of Se distribution was liver > kidney > spleen > cardiac muscle > egg > blood > breast muscle, irrespective of the addition level or source. It was concluded that meat and eggs from hens fed commercial SY are a potential source of Se for humans.

Effects of Different Selenium Sources on Performance, Carcass Characteristics, Plasma Glutathione Peroxidase Activity and Selenium Deposition in Finishing Hanwoo Steers

This study was conducted to determine effects of different selenium (Se) sources on performance, carcass characteristics, blood measures (whole blood Se concentration and plasma glutathione peroxidase (GSH-Px) activity), and Se concentrations in tissues of finishing Hanwoo steers (Korean native steers). Twenty finishing Hanwoo steers (average body weight = 536??3.4 kg, average age = approximately 20 months) were allotted to treatments in four groups of five steers per pen for 16 weeks preceding slaughter. Treatments were control (CON), spent mushroom composts from Se-enriched mushrooms (Se-SMC), selenized yeast (Se-Y), and sodium selenite (SS). Dietary Se levels of all treatments except CON were 0.9 mg Se/kg on the dry matter basis. Body weight was measured at the first and final day of trial, and blood samples were collected to analyze whole blood Se concentration and plasma GSH-Px activity at 2, 4, 8, and 16 weeks. At the end of trial, steers were slaughtered to collect muscle and liver samples for their Se analyses, and carcass data were recorded. In terms of dry matter intake, body weight gain and carcass characteristics, no significant differences among treatments were observed. Whole blood Se concentrations were significantly higher (p<0.05) for Se-SMC and Se-Y treatments than for CON at each collection period, with no significant difference between SS and CON. For weeks 2 and 8, there was no significant difference for whole blood Se concentration between Se-SMC and Se-Y, but for weeks 4 and 16, Se-Y treatments were significantly higher (p<0.05) than Se-SMC. No differences were observed for plasma GSH-Px activity between Se-SMC and Se-Y. The Se concentrations in hind leg and liver were significantly different among treatments (p<0.05) and those in both tissues ranked the greatest in Se-Y, followed by Se-SMC, SS, and CON treatments. However, tissue Se concentration for SS was not different from that for CON. These results showed that feeding organic Se sources such as Se-SMC and Se-Y enhanced Se concentration in tissues, while SS, the most common supplement of inorganic Se, was inefficient in Se deposition. Even though Se-Y had a higher Se concentration in tissues than Se-SMC, replacing Se-Y with Se-SMC in diets of beef steers would be an inexpensive way to increase Se concentration in beef.

Selenium yeast: Composition, quality, analysis, and safety

Abstract Selenium yeast, produced by growing select strains of Saccharomyces cerevisiae in Se-rich media, is a recognized source of organic food-form Se, but the determination of its exact composition with respect to the Se species present produced conflicting results. Improved methods of analysis have since revealed it to contain 90+ % of its Se in the form of selenomethionine, the principal organic nutritional form of Se for higher animals and humans. The safety record of Se yeast is excellent: During the three decades of its world-wide use as a source of supplemental Se, no cases of Se poisoning have occurred due to dosage or formulation errors.

The effect of the heat processing of soybean seed on the metabolism of its selenium in lambs

The effect of the heat processing on the bioavailability of selenium (Se) in soybean seed containing 324 μg Se/kg dry matter (DM), was investigated by measuring the accumulation of Se in rumen bacteria, bodily tissues and whole blood of sheep fed diets containing differently heat processed soybean. Ground soybean seed was subjected to three heat processing treatments; 130 °C for 45 min (considered the ideal treatment); 150 °C for 30 min (over-processed treatment) and the untreated soybeans as the control (unprocessed). The acid detergent insoluble nitrogen (ADIN) concentrations of 32, 180 and 13 g/kg N in the respective heat treated soybeans were used as indication of relative heat damage inflicted on the protein in the soybeans. Thirty weaned Dohne Merino lambs ( ca. 5 months of age, live weight 23.9 ± 0.9 kg) were randomly allocated to three diets containing 436 g/kg of the differently treated soybean. The diets containing ca. 140 μg Se/kg DM, of which 0.95 originated from the soybeans, were fed for 85 days to the lambs after which they were slaughtered. Rumen bacteria from the unprocessed treatment contained a significantly higher concentration of Se (2918 μg/kg DM) compared to the over-processed treatment (2188 μg/kg DM). The liver, cardiac muscle, wool and whole blood from the ideal treatment contained consistently significantly higher concentrations of Se than either or both of the other two treatments, e.g. the liver contained 1535, 1327 and 1555 μg Se/kg DM in the ideal, control and over-processed treatments, respectively, the cardiac muscle 1616, 1527 and 1480 μg Se/kg DM, respectively, and in whole blood at the end of the trial 336, 278 and 265 μg Se/kg, respectively. It was concluded that the heat processing applied to the organic Se source in this trial affected the bioavailability of the Se, but the heat treatments might not have been sufficiently different to manifest distinct differences in the metabolism of Se in the body.

Comparison of inorganic and organic selenium sources for broilers

An experiment was conducted to compare the effects of organic and inorganic sources of Se on growth performance, carcass traits, breast and plasma Se concentrations, and plasma glutathione peroxidase (pGPX3) activity in broilers. Broiler chicks were sexed on d 0 and within sex, randomly allotted to dietary treatment. Average initial and final BW of the broilers were 47 and 2,684 g, and the experiment lasted 49 d. A 3-phase feeding program similar to industry recommendations was used, and the basal diets for each phase were corn-soybean meal based. For each growth phase, the basal diet was supplemented with 0 (control) or 0.30 ppm Se from sodium selenite (SS) or Se-enriched yeast (SY). Each treatment was replicated 7 times (4 pens of males and 3 pens of females) with 50 male or 55 female broilers per replicate. Daily gain, feed intake, gain:feed, eviscerated and chill weights, carcass yield, breast weight, and moisture loss from the breast were not affected (P > 0.05) by Se supplementation. Dietary supplementation with SY increased (P < 0.05) muscle and plasma Se concentrations compared with broilers fed the control diet or the diet with SS. Plasma GPX3 activity was not affected (P > 0.05) by Se source or concentration. The results from this experiment indicate that organic Se increases tissue Se concentration, but it does not affect growth performance, carcass traits, or pGPX3 activity compared with inorganic Se.

Long-term effects of dietary organic and inorganic selenium sources and levels on reproducing sows and their progeny.

An experiment evaluated the effects of feeding either a basal non-Se-fortified diet, two Se sources (organic or inorganic) each providing 0.15 and 0.30 ppm Se, or their combination (each providing 0.15 ppm Se) on gilt growth and sow reproductive performance. The experiment was a 2 x 2 + 2 factorial conducted in a randomized complete block design in three replicates. One hundred twenty-six crossbred gilts were started on one of the six treatment diets at 27.6 kg BW. During the grower phase, animals were bled at 30-d intervals with three gilts killed per treatment at 115 kg BW for tissue Se analysis. Fifteen gilts per treatment were bred at 8 mo of age and were continued on their treatment diets for four parities. Sow serum collected within parity was analyzed for Se and glutathione peroxidase (GSH-Px) activity. Tissue Se was determined from five 0-d-old pigs per treatment from fourth-parity sows. Three sows per treatment were killed after the fourth parity for tissue Se analysis. Similar treatment performance responses occurred from 27 to 115 kg BW. Serum Se (P < 0.01) and GSH-Px activity (P < 0.05) increased for both Se sources to 0.30 ppm Se during the grower and reproductive periods. Serum Se and GSH-Px activity decreased from 70 to 110 d postcoitum in all treatment groups, but increased at weaning (P < 0.01) in the Se-fortified groups. The number of pigs born (total, live) increased (P < 0.05) with the 0.15 ppm Se level for both Se sources. Tissue and total body Se content of 0-d-old pigs increased with Se level (P < 0.01) and also when the organic Se source (P < 0.01) was fed to the sow. When sows were fed either Se source, pig serum Se (P < 0.01) and GSH-Px activity (P < 0.05) increased at weaning. Colostrum and milk Se concentrations increased (P < 0.01) with Se level for both Se sources, but were substantially greater (P < 0.01) when sows were fed organic Se. The combination of Se sources had sow milk and tissue Se values that were similar to those of sows milk and fed 0.15 ppm organic Se. The fourth-parity sows had greater tissue Se concentrations when organic Se level was increased (P < 0.01), more so than when sows were fed inorganic Se. These results suggest that both Se sources resulted in similar sow reproductive performances at 0.15 ppm Se, but sows fed the organic Se source had a greater transfer of Se to the neonate, colostrum, milk, weaned pig, and sow tissues than sows fed inorganic Se.

Chicken Selenium Status when Fed a Diet Supplemented with Se-Yeast

Kuricova S., K. BoldiIarova, a. Gre‰akova, M. Levkut, a. Leng: Chicken Selenium Satus When Fed a Diet Supplemented with Se-Yeast. Acta Vet. Brno 2003, 72: 339-346. This experiment was designed to investigate the effects of the feed supplementation with inorganic and organic forms of Se on the activity of blood glutathione peroxidase (GSH-Px) and the Se levels in blood and tissues in young female chickens of the laying strain Isa Brown. The first group of birds received the basic diet (BD) with Se content 0.12 mg.kg -1 of dry matter (DM). Diets for Groups 1, 2 and 3 consisted of BD supplemented with sodium selenite 0.2 mg·kg-1 of DM, Se-enriched yeast 0.2 and 0.7 mg·kg -1 of DM, respectively. The experiment lasted from hatching until 7 weeks of age. The activity of blood GSH-Px was found to be dose-dependent throughout the experiment with no differences due to the form of Se administered. The selenium analysis in blood and liver samples revealed also the Se dose dependent responses but with significantly higher values recorded in chickens aged 5 weeks and older chickens and supplied with the equivalent amounts of organic Se source. Other tissue Se levels were also highest (P < 0.05) in the group with its largest intake. The values of Se content in the breast muscle were higher (P < 0.001) in chicks of Group 3 during entire experiment and they reached the doubled values than in the birds given selenite (11.54 ± 0.4 vs. 5.47 ± 0.2 µmol·kg-1 of DM, in 7-weekold birds). On the other hand, no differences in this parameter were determined between the chicks fed just BD or BD supplemented with Na 2 SeO 3 . At the end of experiment, the intake of Se-yeast (Group 3) resulted in significantly (P < 0.05) higher Se levels in the heart, in lungs and in the gizzard than BD with selenite. No effects of the form of selenium used could be found in the spleen and kidney samples of 7-week-old chicks. The results demonstrate the evident advantage of supplementation of poultry feed with the selenium-enriched yeast due to more effective Se utilization and formation of mobile body deposits of this microelement than in the case of supplementation with selenite. Poultry, selenium, bioavailability, glutathione peroxidase, striated muscle, liver

Metabolic pathway for selenium in the body: speciation by HPLC-ICP MS with enriched Se

Selenium (Se) is an ultramicro essential nutrient and both inorganic (selenite and selenate) and organic (selenocysteine and selenomethionine) forms of Se can be used as nutritional sources. Metabolic pathways for Se in the body were studied for selenite and selenate, with the use of enriched 82Se, by speciation with separation by gel filtration HPLC and detection by element-specific mass spectrometry with ionization with inductively coupled argon plasma (HPLC-ICP MS). The concentrations of 82Se in organs and body fluids and the distributions of their constituents depending on the dose and time after the intravenous administration of 82Se-selenite and -selenate to rats were determined. Selenite was taken up by red blood cells within several minutes, reduced to selenide by glutathione, and then transported to the plasma, bound selectively to albumin and transferred to the liver. Contrary to selenite, intact selenate was either taken up directly by the liver or excreted into the urine. The 82Se of selenite origin and that of selenate origin were detected in the forms of the two Se peak materials in the liver, A and B. The former one was methylated to the latter in vivo and in vitro. The latter one was identical with the major urinary metabolite and it was identified as Se-methyl- N -acetyl-selenohexosamine (selenosugar). The chemical species-specific metabolic pathway for Se was explained by the metabolic regulation through selenide as the assumed common intermediate for the inorganic and organic Se sources and as the checkpoint metabolite between utilization for the selenoprotein synthesis and methylation for the excretion of Se.

Determination of Selenium Species in Environmental Samples

The essential nature of selenium as well as its toxicity depend on the concentration and the chemical forms in which this element is present in a given sample. Dissolved inorganic selenium can be found in natural water and soil as selenides, selenite and selenate. Organoselenium compounds present in air, soil and plants are volatile methylselenides, trimethylselenonium ion and several selenoamino acids. This review is a summary of recent research on the determination of selenium species in environmental samples such as water, air, soil and plants. Stability of selenium species in solutions and their storage is also discussed. In the metabolic pathway in the body selenide could act as the common intermediate for inorganic and organic Se sources as well as the checkpoint between further utilisation and excretion of selenium.

Effect of organic and inorganic selenium sources and levels on sow colostrum and milk selenium content.

A study was conducted to evaluate the short-term effects of feeding two dietary Se sources at various Se levels on the transfer of Se to the dam's milk and nursing pig. Six dietary treatments were arranged in a 2 x 2 factorial arrangement with two additional treatments in a randomized complete block designed experiment. Inorganic (sodium selenite) or organic (Se-enriched yeast) Se sources were added to the diet at .15 or .30 ppm Se. A non-Se-fortified corn-soybean meal basal diet served as a negative control, and a sixth group was fed .15 ppm Se from both inorganic and organic Se sources. A total of 43 sows were fed their treatment diets at 2.2 kg/d from 6 d prepartum to parturition and at full feed through a 14-d lactation period. Ten sows were initially bled at 6 d prepartum, and three sows and three pigs from their litters were bled at 7 and 14 d postpartum. Serum was analyzed for its Se concentration and glutathione peroxidase (GSH-Px) activity. Colostrum was collected within 12 h postpartum and milk at 7 and 14 d of lactation. When the basal diet was fed, sow serum GSH-Px activity declined from 6 d prepartum and remained low throughout lactation. When dietary Se levels increased, sow serum Se concentration and serum GSH-Px activity increased (P < .05) at both 7 and 14 d postpartum. The short-term feeding of either Se source at .15 or .30 ppm Se did not affect colostrum Se content when inorganic Se was fed, but it was increased when organic Se was provided. This resulted in a significant Se source x Se level interaction (P < .01). Milk Se at 7 and 14 d postpartum was 2.5 to 3 times higher when the organic Se source was provided and resulted in a significant Se source x Se level interaction (P < .05). When the combination of inorganic and organic Se was fed at .15 ppm Se, colostrum and milk Se contents were similar to those of sows fed .15 ppm Se from the organic Se source. Pig serum GSH-Px activity was not affected at 7 and 14 d of age by dietary Se level or Se source fed to the sow, but serum Se increased (P < .05) as dietary Se level increased, particularly when sows had been fed organic Se. The results demonstrated that organic Se increased milk Se content more than did inorganic Se and increased the nursing pig's serum Se. These results indicate that inorganic Se was more biologically available for sow serum GSH-Px activity, but organic Se was more effectively incorporated into milk.

Effects of dietary levels of selenium-enriched yeast and sodium selenite as selenium sources fed to growing-finishing pigs on performance, tissue selenium, serum glutathione peroxidase activity, carcass characteristics, and loin quality.

This research evaluated the efficacy of inorganic and organic Se sources for growing-finishing pigs, as measured by performance and various tissue, serum, carcass, and loin quality traits. A total of 351 crossbred pigs were allotted at an average BW of 20.4 kg to six replicates of a 2x4 factorial experiment in a randomized complete block design. Pigs were fed diets containing Se-enriched yeast (organic) or sodium selenite (inorganic), each at .05, .10, .20, or .30 mg Se/kg diet. A non-Se-fortified basal diet was a ninth treatment group. Five pigs per pen were bled initially and at 30-d intervals with serum analyzed for Se and glutathione peroxidase (GSH-Px) activity. At 55 kg BW, one pig per pen from each of three replicates was killed, and tissues were collected for Se analysis. At 105 kg BW, the remaining pigs in the three replicates were killed, carcass measurements were collected, tissues were analyzed for Se, and loin quality was evaluated for pH, drip loss, and lightness. No performance or carcass measurement benefit resulted from either Se source or dietary Se levels. Pigs had a lower serum Se concentration and GSH-Px activity when the basal diet was fed, but both increased as dietary Se level increased (P<.01). Serum GSH-Px activities were increased by pig age and reached a plateau when the diet contained approximately .10 mg Se/kg (P<.01) at d 30, and 60 of the trial, and at .05 mg Se/kg diet at d 90 of the trial. The organic Se group fed .05 and .10 mg Se/kg had serum GSH-Px activities that tended to be lower than those of pigs fed the inorganic Se source, but GSH-Px activities in both groups were similar at higher Se levels. Tissue Se contents increased linearly as the dietary Se level increased, but the increase was markedly higher when organic Se was fed, resulting in an interaction (P<.01) response. Loin drip loss, pH, and lightness were unaffected (P>.15) by organic Se source or level, but there was a trend for a higher drip loss (P = .11) and a linear (P<.01) increase in loin paleness when the inorganic Se level increased. These results indicate that neither Se source nor Se level had an effect on pig performance or carcass measurements, but organic Se source increased tissue Se concentrations. Inorganic Se may, however, have a detrimental effect on loin quality, as reflected by higher drip loss and a paler color. Using serum GSH-Px activity as the measurement criterion, the supplemental dietary Se requirement did not seem to exceed .10 and .05 mg Se/kg diet for the growing and finishing phases, respectively, when added to a basal diet containing .06 mg Se/kg.

Diffusibility of selenate, selenite, seleno-methionine, and seleno-cystine during simulated gastrointestinal digestion.

The present study was undertaken to evaluate the in vitro availability of chemically varying forms of selenium (Se), supplemented in cow's milk. Two inorganic (selenite and selenate) and two organic (seleno-methionine [Se-Met] and seleno-cystine [Se-Cys]) Se sources were evaluated. The in vitro availability was estimated by the diffusibility of Se during simulated gastrointestinal digestion. First, the diffusibility was compared after adding a constant amount of Se as either selenate, selenite, seleno-methionine, or Se-Cys in milk samples. Se-Met and selenate were found to be significantly more diffusible than seleno-cystine and selenite under the simulated gastrointestinal conditions. The tendency for superior in vitro availability of selenate and Se-Met compared to selenite and Se-Cys was confirmed for a supplementation range of 5-40 ng/g of Se. This study suggests that the high diffusibility of selenate and Se-Met in a simulated gastrointestinal environment may contribute to their high absorption in vivo.

Metabolism of selenite, selenomethionine and feed-incorporated selenium in lactating goats and dairy cows

The objective of this study was to investigate the metabolism of inorganic and organic Se sources at different dietary Se levels in lactating goats and dairy cows. The study consists of two experiments on goats dosed singly, either orally with grass sprayed with Na275SeO3 one week before cutting, intraruminally (I.R.) with Na275SeO3, or intravenously (I.V.) with Na275SeO3 or 75Se-selenomethionine. Follow-up periods were from 15 to 28 d long. Dietary Se levels were 0.05, 0.22 and 0.34 mg/kg DM. Values for 75Se absorption, excretion in milk, urine and faeces, 75Se activity in plasma, erythrocytes and hair are presented. In another experiment lasting 539 d, 48 dairy cows were fed either Na275SeO3 or grass silage sprayed with Na275SeO3 one week before cutting. Dietary Se levels were from 0.03 to 1.8 mg/kg DM. Se content in milk, plasma and erythrocytes, and GSH-Px activity in erythrocytes and plasma are given. True absorption of 75Se was 63 % and 65 %, and excretion of 75Se in milk 4 % and 7 % in the goats dosed I.R. with Na275SeO3 and orally with 75Se-labeled grass. The effect of dietary Se content was non-significant. After I.V. dose, 3.6 % and 33 % of 75Se was excreted in milk in goats dosed with Na275SeO3 and 75Se-selenomethionine, respectively, Na275SeO3 being eliminated mainly via urine. In cows receiving selenium as Na275SeO3, milk contained 0.011, 0.011, 0.016 and 0.020 mg Se/l at dietary Se levels 0.11, 0.17, 0.42 and 0.68 mg/kg DM, respectively. In cows receiving Se-sprayed silage, milk Se content was 0.023, 0.020, 0.029 and 0.040 mg/l when the diet contained 0.09, 0.20, 0.45 and 1.20 mg Se/kg DM. Se incorporated into silage was more efficient (p