Biochemical and physiological indicators of selenium status in animals

Evaluation of selenium source on nursery pig growth performance, serum and tissue selenium concentrations, and serum antioxidant status

A total of 3,888 pigs (337 × 1050, PIC, Hendersonville, TN; initially 6.0 ± 0.23 kg) were used in a 35-d study. At the time of placement, pens of pigs were weighed and allotted to one of three dietary treatments in a randomized complete block design with a blocking structure including sow farm origin, date of entry into the facility, and average pen body weight. A total of 144 pens were used with 72 double-sided 5-hole stainless steel fence line feeders, with one feeder serving as the experimental unit. For each feeder, 1 pen contained 27 gilts, and 1 pen contained 27 barrows. There were 24 replicates per dietary treatment. Diets were fed in three phases, and all contained 0.3 mg/kg added Se. A common phase 1 diet contained added Se from sodium selenite and was fed in pelleted form to all pigs from day 7 to approximately day 0. Three Se sources sodium selenite, Se yeast, and hydroxy-selenomethionine (OH-SeMet) were used to formulate three experimental diets in meal form for phase 2 (days 0 to 14) and phase 3 (days 14 to 35). During the pre-treatment period (days 7 to 0), there was a tendency (P = 0.097) of a difference in average daily feed intake between treatments, although no significant pairwise differences were observed (P > 0.05). There were no other differences in growth performance between treatments from days 7 to 0. Clinical disease attributed to Streptococcus suis was observed within the trial between days 0 and 14, and water-soluble antimicrobial therapy was administered to all treatment groups for 7 d. From days 0 to 35, pigs fed OH-SeMet tended to have decreased average daily gain (P < 0.10) and increased (P < 0.05) serum and tissue selenium concentration compared to other treatments. There was marginally significant evidence of a source × day interaction (P = 0.027) for total antioxidant capacity where the numerical increase over time was less for the OH-SeMet than sodium selenite or selenium yeast treatments. There was no difference (P > 0.05) in antioxidant status as measured by serum glutathione peroxidase or thiobarbituric acid reactive substances assay between treatments. In summary, compared to sodium selenite and selenium yeast, OH-SeMet may have a greater bioavailability as indicated by increased serum and tissue selenium concentration; however, antioxidant status was similar between treatments and OH-SeMet tended to reduce growth performance compared with pigs fed sodium selenite.

Plasma and Colostrum Selenium Statuses of Properly Supplemented Belgian Blue Cows on Commercial Farms and Their Relationship with Sources of Dietary Selenium and Blood Biomarkers

Selenium (Se) is an essential trace element for the health and immunity of cattle. Double-muscled Belgian Blue cows are well known to be prone to nutritional deficiencies. Colostrum Se level is also a key factor to promote immunoglobulin intake in young calves. The main objectives of this study were to assess (1) the plasma and colostrum Se statuses of properly supplemented Belgian Blue cows on commercial farms and (2) the relationship between Se concentrations in plasma and colostrum. The secondary objectives were to assess relationships between plasma or colostrum Se concentrations and dietary Se supplementation as well as blood biomarkers. Blood and colostrum samples were collected from 49 Belgian Blue cows on five commercial farms in Belgium. They received five different rations with Se supplementation ranging from 0.5 to 2 ppm, including 20% to 83% in organic form. Results showed that the average Se concentration was 90 ± 15 µg/L in plasma and 79 ± 26 µg/L in colostrum, consistent with previous studies on well-supplemented cows. No relationship was observed between Se concentrations in plasma and colostrum, suggesting that colostrum Se testing would be a complementary indicator for improving calf Se supplementation. Relationships between plasma or colostrum Se concentrations and dietary Se or blood biomarkers emphasized the complexity of Se metabolism in observational studies under field conditions.

Different Effects of Low Selenite and Selenium-Nanoparticle Supplementation on Adipose Tissue Function and Insulin Secretion in Adolescent Male Rats

Adolescence is a period of intense growth and endocrine changes, and obesity and insulin-resistance processes during this period have lately been rising. Selenium (Se) homeostasis is related to lipid metabolism depending on the form and dose of Se. This study tests the actions of low-dose selenite and Se nanoparticles (SeNPs) on white (WAT) and brown adipose tissue (BAT) deposition, insulin secretion, and GPx1, IRS-1 and FOXO3a expression in the WAT of adolescent rats as regards oxidative stress, adipocyte length and adipokine secretion. Four groups of male adolescent rats were treated: control (C), low selenite supplementation (S), low SeNP supplementation (NS) and moderate SeNP supplementation (NSS). Supplementation was received orally through water intake; NS and NSS rats received two- and tenfold more Se than C animals, respectively. SeNPs were obtained by reducing Se tetrachloride in the presence of ascorbic acid. For the first time in vivo, it was demonstrated that low selenite supplementation contributed to increased adipogenesis via the insulin signaling pathway and LCN2 modulation, while low SeNP administration prevented fat depots in WAT via the decrease in insulin signaling and FOXO3a autophagy in WAT, lowering inflammation. These effects were independent of GPx1 expression or activity in WAT. These findings provide data for dietary approaches to prevent obesity and/or anorexia during adolescence. These findings may be relevant to future studies looking at a nutritional approach aimed at pre-venting obesity and/or anorexia in adolescence.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

Selenkonzentration im Serum und Glutathionperoxidaseaktivität im Vollblut bei gesunden adulten Pferden

Gegenstand und Ziel: Überprüfung des Selenstatus von Pferden anhand der Konzentration von Selen (Se) im Serum und der Glutathionperoxidaseaktivität im Vollblut (GPx) zur Ableitung von Referenzbereichen. Material und Methoden: Warmblutpferde aus zwei Betrieben wurden bis zu viermal im Abstand von mindestens 3 Monaten beprobt. Für einen Rassenvergleich fand in drei Betrieben einmalig eine Blutprobenentnahme bei Vollblutpferden, Islandpferden bzw. Kaltblütern statt. Daraus resultierten insgesamt 1167 Blutproben von 528 klinisch gesunden Pferden. Die-Se-Konzentration wurde massenspektrometrisch analysiert, die GPx-Aktivität in heparinisiertem Vollblut photometrisch gemessen und auf den Hämatokrit bezogen. Das Referenzintervall umfasst die zentralen 95% der Werte aller gesammelten Proben adulter (Alter > 1 Jahr) Warmblüter. Ergebnisse: Die Se-Konzentration im Serum betrug 96 ± 38 µg/l, die GPx-Aktivität im Vollblut 94 ± 40 U/ml Hkt (Mittelwert ± Standardabweichung; n = 1167). Bei 48% der Pferde ergaben sich Se-Werte unterhalb des aktuellen Referenzbereichs von 100–200 µg/l. Alter, Rasse, Standort, Fütterung und Jahreszeit hatten einen Einfluss auf den Se-Status der Pferde. Die Korrelation zwischen der GPx-Aktivität und der Se-Konzentration ließ sich mit der linearen Regressionsgleichung y = 0,73 x + 23,76 beschreiben (y = GPx-Aktivität, x = Se) und es bestand eine signifikante positive Korrelation von r = 0,7. Der aus allen Proben (n = 909) adulter Warmblutpferde berechnete Bereich zwischen 2,5%- und 97,5%-Perzentil betrug für die Se-Konzentrationen 34–167 µg/l und für die GPx-Aktivität 34–175 U/ml Hkt. Schlussfolgerung und klinische Relevanz: Aufgrund der hohen prozentualen Anteils gesunder Pferde, deren Se-Werte nicht im Referenzbereich lagen, scheint der bisher geltende Referenzbereich von 100–200 µg/l zu hoch angesetzt zu sein. Anhand der erhobenen Werte wird für die Se-Konzentration im Serum ein Referenzbereich von 70–170 µg/l vorgeschlagen. Als ergänzender Parameter lässt sich die GPx-Aktivität im Vollblut nutzen, für die ein Referenzbereich von 50–175 U/ml Hkt empfohlen wird.

Effect of parenteral selenium administration on oxidative status of weaned piglets

The aim of the study was to evaluate the effect of additional selenium injection after weaning on the selenium (Se) status of piglets and to find whether the selected dose would be appropriate with respect to the level of oxidative stress. Another goal was to compare the efficacy and safety of sodium selenite and selenopyran as selenium sources for parenteral administration to piglets. Altogether 30 piglets were divided equally into three groups. Piglets in group 1 were injected i.m. with sodium selenite, piglets in group 2 were injected with selenopyran. The dose was 0.42 mg Se/kg body weight for both groups. Piglets in group 3 were given only saline. As expected, the study revealed low Se serum concentrations in weaned piglets. The injection of sodium selenite increased Se serum concentrations but did not have a positive effect on the peroxidase activities. Administration of selenopyran did not influence Se concentrations and gluthation peroxidase activities. The selected dose did not have a significant impact on the level of the oxidative stress. The piglets receiving Se only from the feed achieved comparable gluthation peroxidase activities during the trial. It seems that despite initially low Se concentrations, the physiological requirements for gluthation peroxidase synthesis were met with the feed consumption as the only Se source. The results of the study are important because until now it was unclear whether the selected dose would have negative effects on the organism with respect to the induction of oxidative stress in piglets.

Selenium deficiency associated porcine and human cardiomyopathies

Selenium (Se) is a trace element playing an important role in animal and human physiological homeostasis. It is a key component in selenoproteins (SeP) exerting multiple actions on endocrine, immune, inflammatory and reproductive processes. The SeP family of glutathione peroxidases (GSH-Px) inactivates peroxides and thereby maintains physiological muscle function in humans and animals. Animals with high feed conversion efficiency and substantial muscle mass have shown susceptibility to Se deficiency related diseases since nutritional requirements of the organism may not be covered. Mulberry Heart Disease (MHD) in pigs is an important manifestation of Se deficiency often implicating acute heart failure and sudden death without prior clinical signs. Post-mortem findings include hemorrhagic and pale myocardial areas accompanied by fluid accumulation in the pericardial sac and pleural cavity. Challenges in MHD are emerging in various parts of the world. Se is of fundamental importance also to human health. In the 1930s the Se deficiency associated cardiomyopathy named Keshan Disease (KD) was described for the first time in China. Various manifestations, such as cardiogenic shock, enlarged heart, congestive heart failure, and cardiac arrhythmias are common. Multifocal necrosis and fibrous replacement of myocardium are characteristic findings. Pathological findings in MD and KD show striking similarities.

Hepatic transcriptome profiles differ among maturing beef heifers supplemented with inorganic, organic, or mixed (50% inorganic:50% organic) forms of dietary selenium

Selenium (Se) is an important trace mineral that, due to deficiencies in the soil in many parts of the USA, must be supplemented directly to the diet of foraging cattle. Both organic and inorganic forms of dietary Se supplements are available and commonly used, and it is known that Se form affects tissue assimilation, bioavailability, and physiological responses. However, little is known about the effects of form of dietary Se supplements on gene expression profiles, which ostensibly account for Se form-dependent physiological processes. To determine if hepatic transcriptomes of growing beef (Angus-cross) heifers (0.5 kg gain/day) was altered by form of dietary supplemental Se, none (Control), or 3 mg Se/day as inorganic Se (ISe, sodium selenite), organic (OSe, Sel-Plex®), or a blend of ISe and OSe (1.5 mg:1.5 mg, Mix) Se was fed for 168 days, and the RNA expression profiles from biopsied liver tissues was compared by microarray analysis. The relative abundance of 139 RNA transcripts was affected by Se treatment, with 86 of these with complete gene annotations. Statistical and bioinformatic analysis of the annotated RNA transcripts revealed clear differences among the four Se treatment groups in their hepatic expression profiles, including (1) solely and commonly affected transcripts; (2) Control and OSe profiles being more similar than Mix and ISe treatments; (3) distinct OSe-, Mix-, and ISe-Se treatment-induced "phenotypes" that possessed both common and unique predicted physiological capacities; and (4) expression of three microRNAs were uniquely sensitive to OSe, ISe, or Mix treatments, including increased capacity for redox potential induced by OSe and Mix Se treatments resulting from decreased expression of MiR2300b messenger RNA. These findings indicate that the form of supplemental dietary Se consumed by cattle will affect the composition of liver transcriptomes resulting, presumably, in different physiological capacities.

Microencapsulated sodium selenite supplementation in dairy cows: effects on selenium status

The objective of this study was to compare the efficiency of transfer of selenium (Se) to plasma and milk from inorganic sodium selenite, either free or microencapsulated, and from selenized yeast in dairy cows. The study consisted of an in situ-nylon bags incubation, and in an in vivo experiment to compare the Se status of cows supplemented with either sodium selenite, microencapsulated sodium selenite, or Se yeast. Thirty dairy cows, divided in five groups, were fed the following diets: the control group (CTR) received a total mixed ration supplemented with sodium selenite in order to have 0.3 mg/kg DM of total Se; 0.3M and 0.5M groups received the same control diet supplemented with lipid microencapsulated sodium selenite to provide 0.3 and 0.5 mg/kg DM of total Se, respectively; 0.3Y and 0.5Y groups received selenized yeast to provide 0.3 and 0.5 mg/kg of total Se, respectively. Cows were fed the supplements for 56 days during which milk, blood, and fecal samples were collected weekly to conduct analysis of Se and glutathione peroxidase (GSH-px) activity. Se concentration in the nylon bags was assessed to 72%, 64%, and 40% of the initial value (time 0) after 4, 8, and 24 h of incubation, respectively. In vivo, cows supplemented with 0.3 mg/kg of microencapsulated Se had higher milk Se concentration compared to CTR. The increment was more pronounced at the highest inclusion rate (0.5 mg/kg, 0.5M group). GSH-px activity was not significantly affected by treatments. The results indicate that lipid microencapsulation has the potential to protect nutrients from complete rumen reduction and that Se from microencapsulated selenite is incorporated in milk more efficiently than the free form. Microencapsulated sodium selenite was shown to be comparable to Se-yeast in terms of availability and incorporation in milk when fed at 0.3 mg/kg DM, whereas the inclusion in the diet at 0.5 mg/kg DM resulted in higher plasma and milk concentrations than selenized yeast.

Selenium blocks porcine circovirus type 2 replication promotion induced by oxidative stress by improving GPx1 expression

Porcine circovirus type 2 (PCV2) is recognized as a key infectious agent in postweaning multisystemic wasting syndrome (PMWS), but not all pigs infected with PCV2 will develop PMWS. The aim of this work was to explore the relationships among PCV2 infection, oxidative stress, and selenium in a PK-15 cell culture model of PCV2 infection. The results showed that oxidative stress induced by H(2)O(2) treatment increased PCV2 replication as measured by PCV2 DNA copies and the number of infected cells. Furthermore, PCV2 replication was inhibited by selenomethionine (SeMet) at a high concentration (6μM) and the increase in PCV2 replication by oxidative stress was blocked by SeMet at physiological concentrations (2 or 4μM). PCV2 infection caused a decrease in glutathione peroxidase 1 (GPx1) activity but an increase in GPx1 mRNA levels, suggesting that GPx1 may represent an important defense mechanism during PCV2 infection. SeMet did not significantly block the promotion of PCV2 replication in GPx1-knockdown cells. This observation correlates with the observed influence of SeMet on GPx1 mRNA and activity in GPx1-knockdown cells, indicating that GPx1 plays a key role in blocking the promotion of PCV2 replication. We conclude that differences in morbidity and severity of PMWS observed on different pig farms may be related to variations in oxidative stress and that selenium has a potential role in the control of PCV2 infection.

Selenium content in blood fractions and liver of beef heifers is greater with a mix of inorganic/organic or organic versus inorganic supplemental selenium but the time required for maximal assimilation is tissue-specific

Selenium (Se) content of feedstuffs is dependent on the Se level of the soil. Even though Se in grass and forage crops is primarily present in organic forms, Se is commonly supplemented in cattle diets in an inorganic (sodium selenite) form in geographic regions where Se soil concentrations are low. The purpose of this study was to answer two important questions about inorganic (ISe) vs organic (OSe) forms of dietary supplementation of Se (3 mg/day) to growing beef heifers (0.5 kg/day): (1) what would the effect of supplementing Se with an equal blend of ISe:OSe (Mix) have on Se tissue concentrations and (2) how long does it take for the greater assimilation with OSE to occur and stabilize? A long-term (224 day) Se dietary supplementation trial was conducted with serial sampling performed (days 28, 56, 112, and 224) to determine the length of time required to achieve Se supplement (OSE, Mix, and ISe)-dependent changes in Se assimilation in blood fractions and liver tissue. Forty maturing Angus heifers were fed a corn silage-based diet for 98 days with no Se supplementation, and then a cracked corn/cottonseed hull-based diet (basal diet) without Se supplementation for 74 days. Liver biopsies were taken for Se analysis, and heifers were fed the same diet for another 14 days. Heifers were assigned (n = 10) to one of four Se treatment groups such that basal liver Se contents were stratified among groups, and then fed enough of the basal diet (0.08 mg Se per day) and a mineral-vitamin mix that provided 0.16 (control) or 3.0 mg Se per day in ISe (sodium selenite), OSe (Sel-Plex(®)), or Mix (1:1 ISe:OSe) form to support 0.5 kg/day growth for 224 days. More Se was found in whole blood, red blood cells, serum, and liver of Mix and OSe heifers than ISe heifers, and all were greater than control. Se content either increased until day 56 then was stable (liver and plasma), or was stable until day 56 (whole blood) or day 112 (red blood cells) and then increased steadily through day 224, for all supplemental Se treatments. These data indicate that a 1:1 mix (1.5 mg Se:1.5 mg Se) of supplemental ISe and OSe is equal to 3 mg/day OSe supplementation and greater than 3 mg/day ISe supplementation. The data also indicate that Se levels stabilized in liver and plasma by 56 to 112 days whereas whole blood and red blood cell concentrations were still increasing through 224 days of supplementation, regardless of the form of supplemental Se.

Selenium deficiency alters epithelial cell morphology and responses to influenza

It is unknown whether nutritional deficiencies affect the morphology and function of structural cells, such as epithelial cells, and modify the susceptibility to viral infections. We developed an in vitro system of differentiated human bronchial epithelial cells (BEC) grown either under selenium-adequate (Se+) or selenium-deficient (Se-) conditions, to determine whether selenium deficiency impairs host defense responses at the level of the epithelium. Se- BECs had normal SOD activity, but decreased activity of the selenium-dependent enzyme GPX1. Interestingly, catalase activity was also decreased in Se- BECs. Both Se- and Se+ BECs differentiated into a mucociliary epithelium; however, Se- BEC demonstrated increased mucus production and increased Muc5AC mRNA levels. This effect was also seen in Se+ BEC treated with 3-aminotriazole, an inhibitor of catalase activity, suggesting an association between catalase activity and mucus production. Both Se- and Se+ were infected with influenza A/Bangkok/1/79 and examined 24 h postinfection. Influenza-induced IL-6 production was greater while influenza-induced IP-10 production was lower in Se- BECs. In addition, influenza-induced apoptosis was greater in Se- BEC as compared to the Se+ BECs. These data demonstrate that selenium deficiency has a significant impact on the morphology and influenza-induced host defense responses in human airway epithelial cells.

Vitamin E and selenium plasma concentrations in weanling pigs under field conditions in Norwegian pig herds

BACKGROUND

The status of alpha-tocopherol (vit E) and selenium (Se) has been shown to influence disease resistance in pigs, and may be important for the health of weanling pigs.

METHODS

Plasma levels of both vit E and Se were followed in weanling pigs under field conditions in six Norwegian pig herds. Plasma vit E and Se were measured in 3 sows from each herd and 4 piglets in the litter of each sow at the day before weaning (day -1); and in the same piglets at days 4, 8 and 18 after weaning.

RESULTS

Mean plasma vit E was 4.0 microg/ml in the sows and 2.6 microg/ml in the piglets at day -1, fell to 1.6 microg/ml in the weanling pigs at day 4, and remained low. Mean plasma Se was 0.22 microg/g in the sows and 0.08 microg/g in the piglets at day -1, rose to 0.10 microg/g in the weanlings at day 4, and continued rising.

CONCLUSION

The results suggest that vit E and Se supplementation to piglets and weanling pigs in Norway may still be suboptimal, but that levels of the two nutrients partially compensate for each other in the weaning period.

Selenium supplementation and selenium status of dairy cows fed diets based on grass, grass silage or maize silage

In three separate trial series (TS) the effect of diet composition on selenium (Se) status of dairy cows were investigated. Diets were formulated based mainly on grass (TS1), grass silage (TS2) or maize silage (TS3) with different levels of Se supplementation. Each TS comprised a total of 30 dairy cows and contained one treatment group without Se supplementation (control) and two groups with increasing levels of Se supplementation (levels 1 and 2). Selenium was administered as Na-selenite. The control groups of the different TS showed a very low Se supply of 38-54 microg Se/kg DM. At level 1 the Se supply was increased to 102-165 microg Se/kg DM and at level 2 was 294-373 microg Se/kg DM. After completion of the 6-week trials the average plasma Se concentration of the control cows (without Se supplementation) across all TS was 21.5 microg/l; this increased significantly following Se supplementation, to 37.7 microg/l at level 1 and 61.5 microg/l at level 2. The plasma glutathione peroxidase (GSH-Px) activity of the control cows averaged 67 U/l, rising considerably after supplementation at level 1 to a value of 101 U/l, but showed little further increase at level 2 with a mean value of 120 U/l. By contrast, the average Se content of the milk was unchanged in the control and level 1 groups at 10.5 microg/kg and 10.9 microg/kg, respectively, and only increased markedly after supplementation at level 2 to a mean value of 15.1 microg/kg. The diet based on maize silage, while having a similar Se content as the grass and grass silage-based diets, resulted in a slightly improved Se status, which is due to a higher Se intake from soybean meal.

Selenium and vitamin E

Deficiency of selenium and vitamin E has recently been identified as a major health concern of sheep producers in certain regions of the United States, and familiarity with published data on these nutrients seems to be of value to small ruminant practitioners. This article begins with a description of the biochemical roles and metabolism of selenium and vitamin E. A literature review follows in which the influence of these nutrients on the musculoskeletal, reproductive, and immune systems, as well as on flock productivity, is discussed. Methods for detection of deficiency and supplementation strategies are also described.

Areas with high concentrations of selenium in the soil and forage produce beef with enhanced concentrations of selenium

Beef provides a significant portion of human dietary selenium (Se), and it is possible that modest portions of beef produced in areas with high-Se soil and forage could provide the entire Recommended Dietary Allowance (RDA) for Se. The present study has addressed the environmental conditions that resulted in the production of high-Se beef. One hundred and thirty-eight cull cows were obtained from 21 ranches in five distinct geographic regions that, on the basis of soil parent material, reports of Se deficiency, and previous soil and forage Se surveys, were likely to have high or low Se concentrations in the soil. Grass and soil samples were taken from ranch sites, and hair, whole blood, skeletal muscle, diaphragm muscle, and liver samples were obtained from the animals. Hair and whole blood samples were taken 1 day prior to shipping. Selenium concentrations of all samples were determined by hydride generation atomic absorption spectroscopy. Geographic origin affected Se content of all samples (p < 0.05). Selenium concentrations in soil (r = 0.53; p < 0.01) and grass (r = 0.63; p < 0.01) were correlated to Se content of skeletal muscle. Selenium concentrations in whole blood, diaphragm, hair, and liver also were significantly correlated to Se content of skeletal muscle (p < 0.01). Cows that received Se in mineral supplements did not have significantly higher concentrations of Se in sampled tissues (p > 0.05). Results of this study suggest that the greatest source of variation in Se content of bovine skeletal muscle was the geographic region from which the beef originated and not production or management practices. Results also demonstrated that a 100 g serving of high-Se beef could provide 100% of the RDA for Se.

Selenite and selenium yeast as feed supplements to growing fattening pigs

Twenty-four cross-bred fattening pigs weighing, on average, 24 kg were divided into three equal groups and fed a basic diet containing 0.1 mg selenium/kg. The diet of group A was supplemented with 0.3 mg selenium/kg derived from selenium yeast, group B with 0.1 mg selenium/kg from the same source, and group C with 0.3 mg/kg from sodium selenite. The pigs were slaughtered after 103 days. There was no significant difference between the mean whole blood selenium concentration of the pigs supplemented with selenium yeast neither after five nor after nine weeks of supplementation (group A, 201 and 213 micrograms/litre; group B 192 and 201 micrograms/litre, respectively), but the group supplemented with selenite had significantly lower concentrations both after five and nine weeks (158 and 159 micrograms/litre, respectively). There were no significant differences between the mean activity of glutathione peroxidase (GSH-Px; in the whole blood of the three groups (group A, 348 and 327 mukat*/litre, group B, 342 and 302 mukat/litre; group C, 332 and 300 mukat/litre, after five and nine weeks, respectively). The concentration of selenium in the liver of the pigs supplemented with organic selenium was significantly higher than in the pigs supplemented with selenite (group A, 0.54 mg/kg wet weight; group B, 0.54 mg/kg; group C, 0.40 mg/kg). No deposits of lipofuscin or ceroid pigments were observed in the histological preparations of liver and heart from any of the pigs.

Effects of monensin on the metabolism of periparturient dairy cows

The effects of monensin on plasma concentrations and changes in plasma concentrations of energy metabolites and minerals over time were investigated using 24 multiparous Holstein cows. Cows were paired according to farm, predicted date of calving, and body condition score and were randomly allocated to two groups. Treated cows were given a ruminal bolus containing 32 g of monensin at 50 +/- 7 d before predicted calving. Treated cows had lower plasma concentrations of glucose, free fatty acid (FFA), and beta-hydroxybutyrate (BHBA) than did control cows before calving, indicating that monensin influenced energy metabolism. However, no significant differences in plasma concentrations of glucose, FFA, and BHBA were found between groups after calving. Plasma BHBA concentrations increased more before calving in control cows, and plasma FFA and urea concentrations increased significantly before calving in all cows. No significant differences in body weight, plasma concentrations of urea, or whole blood concentrations of glutathione peroxidase were detected between groups before or after calving. Plasma ceruloplasmin activity did not differ between groups before calving, but was significantly higher in treated cows after calving. Plasma concentrations of Ca did not significantly differ between groups before or after calving. Monensin altered both energy and mineral metabolism and has the potential to improve the health and production of dairy cows.

A compartmental model depicting short-term kinetic changes in selenium metabolism in ewes fed hay containing normal or inadequate levels of selenium

Changes in Se metabolism were studied in ewes fed hay containing normal or inadequate levels of Se. After intravenous injection of 75Se-sodium selenite, blood, feces and urine were collected at different times, and the concentrations of labeled and unlabeled Se were determined. Ewes were killed 1, 5, 9 or 14 d after tracer injection, and tissues were obtained for determination of radioactivity and Se concentration. The data were fitted to a compartmental model using the SAAM/CONSAM computer program, and kinetic parameters and steady-state transport rates were estimated. Daily Se intake (Vi) and fecal excretion (VF) were significantly (P < 0.001) higher in the ewes fed normal hay (6.06 +/- 1.09 and 3.36 +/- 0.88 mumol/d, respectively) than in those fed Se-deficient hay (0.64 +/- 0.18 and 0.26 +/- 0.15 mumol/d). The net absorption (Va) of Se was significantly higher in ewes fed normal hay [3.19 +/- 0.82 mumol/d by the balance method, Va = Vi-(VF -Vf) (Vf = endogenous fecal Se) and 1.05 +/- 0.38 mumol/d by using the model (plasma entry rate, U(1))] than in those fed hay deficient in Se [0.57 +/- 0.33 mumol/d (balance) and 0.28 +/- 0.08 mumol/d (model)]. The efficiency of absorption [alpha = U(1) divided by Vi] was significantly higher (0.46 +/- 0.19) in ewes fed Se-deficient hay than in those fed normal hay (0.18 +/- 0.09). Simultaneous fitting of the tracer data of both the groups showed that changes in hepatic extraction and urinary and fecal excretion were sufficient and necessary to account for the kinetic differences observed between treatments.

The possible role of selenium in antioxidation in marine waders; a preliminary study

In a marine wader, the oystercatcher (Haematopus ostralegus), the activity of the selenium-dependent enzyme glutathione peroxidase (GSH-Px) in the red blood cells (RBC) was measured. The average activity, 97 +/- 19 units/g Hb, is within the range reported for mammals. No correlation was observed between the selenium concentration and GSH-Px activity in the erythrocytes and it is calculated that only a small percentage of the selenium present in the RBC is bound to the enzyme. Therefore, it is concluded that the high selenium concentrations in the avian red cells cannot be ascribed to GSH-Px. It is argued that a function of selenium in antioxidation is still possible. The positive relationship found between selenium and iron concentrations in the tissues of the oystercatcher directs to such a role. A pitfall in the measurement of GSH-Px activity is outlined.

Effect of various dietary selenium (Se) intakes on tissue Se levels and glutathione peroxidase activities in lambs

Experiments were conducted to examine selenium (Se) metabolism in tissues of lambs following Se supplementation at varying doses. For three months four groups of lambs were fed either a basal diet (group A) containing 0.082 mg Se per kg dry matter (ppm) or the same diet plus mineral mixture with Se (as selenite) so that the total diet contained 0.25, 0.41 and 0.58 ppm Se (groups B, C and D, respectively). After three months six lambs of each group were slaughtered and tissues were removed for Se level and GSH-Px activity determinations. Among the tissues of lambs fed the basal diet the highest Se concentration was found in the kidney (1.32 micrograms/g wet weight), and the lowest in the skeletal muscle (0.030 micrograms/g wet weight). In the liver, heart, lung and spleen Se concentrations were almost at the same level and varied in the range of 0.14 to 0.18 micrograms/g wet weight tissue. No increase in Se concentration was found in the kidneys of Se-supplemented animals. Se concentration in the liver and lung increased linearly with the Se level in the diet. In the spleen, heart and skeletal muscle the highest Se concentrations were found in lambs fed 0.41 ppm Se. Tissue GSH-Px activities (calculated on the per g protein basis) increased significantly in Se-treated animals. In the tissues of lambs fed 0.25 ppm Se the enzyme activities were higher in a range of 1.8 to 3.5 as compared to the group fed the basal diet. Higher doses of dietary Se had much smaller effect on the tissues GSH-Px activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutrition and reproduction in dairy cows

Diagnosis of nutritional effects on herd fertility requires a systematic analysis of reproductive records in addition to quantifying the feeding program on the farm. Corroborative laboratory tests for specific deficiencies may be useful.

Trace element deficiencies in cattle

Deficiency of cobalt, copper, iron, iodine, manganese, selenium, or zinc can cause a reduction in production. Reduced production occurs most commonly when a deficiency corresponds to the phases of growth, reproduction, or lactation. Because of environmental, nutrient, disease, genetic, and drug interactions, deficiencies of single or multiple elements can occur even when the levels recommended by the National Research Council for these nutrients are being fed. Additionally, random supplementation of trace elements above National Research Council recommendations is not justified because of the negative interaction among nutrients and potential toxicosis. Evaluation of trace element status can be difficult because many disease states will alter blood analytes used to evaluate nutrient adequacy. Proper dietary and animal evaluation, as well as response to supplementation, are necessary before diagnosing a trace element deficiency.

Clinical nutrition of adult horses

Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cases with renal failure, protein, calcium, and phosphorus should be restricted to maintenance or lower levels. Grass hay and corn are the best feeds for horses with reduced renal function. Do not offer free-choice salt to horses with dependent edema from uncompensated chronic heart failure. Following gastrointestinal resection, legume hay and grain mixtures are the feeds of choice. Horses with diarrhea should not be deprived or oral or enteral alimentation for prolonged periods of time. Liquid formulas may be used if bulk or gastrointestinal motility are a problem. Apple cider vinegar and a high grain diet may reduce the incidence of enteroliths in horses prone to this problem. Pelleted feeds will reduce fecal volume and produce softer feces for horses that have had rectovaginal lacerations or surgery. Horses with small intestinal dysfunction or resection should be offered low residue diets initially, but long-term maintenance requires diets that promote large intestinal digestion (alfalfa hay, vegetable oil, restricted grain). Geriatric horses (greater than 20 years old need diets similar to those recommended for horses 6 to 18 months old.

Selenium: clinical significance and analytical concepts

Selenium is an essential trace element in humans and animals. Its only established function in humans is the antioxidant activity of glutathione peroxidase, a selenoenzyme. Severe prolonged deficiency may cause a fatal cardiomyopathy. Iatrogenic causes of selenium deficiency include parenteral and enteral nutrition. Low plasma selenium is also found in malabsorption, cystic fibrosis, rheumatoid arthritis, neoplasia, and other varied clinical disorders. Death has resulted from a single massive ingestion of selenium, while chronic excessive intake causes skin, nail, and hair pathology. Extreme geographical variation in population blood and urine selenium levels and a marked age-specific variation in population reference intervals are important factors in understanding selenium nutrition. Nutritional requirements, biological availability, and metabolism are discussed in relation to geographical, age, and method variability. Sampling, processing procedures, and methods for selenium quantitation are reviewed. Selenium content in different biological matrices and reference values for pediatric, adult, and obstetric populations are provided.