The selenium intake of the female chicken influences the selenium status of her progeny

The primary purpose of this study is to determine the extent to which the effects of dietary supplementation of the female chicken with selenium (Se) continue into the next generation. An additional aim is to compare the relative effectiveness of pre-hatch (from the hen's diet) with that of post-hatch (from the progeny's diet) supplementation with Se on the Se status of the chick during the first 4 weeks of post-hatch life. Hens were maintained on control or Se-supplemented diets, respectively containing 0.027 and 0.419 μg Se/g of feed. The high-Se diet elevated the Se content of the hens' eggs by 7.1-fold. At hatch, the concentrations of Se in the liver, breast muscle and whole blood of the chicks originating from the high-Se parents were, respectively, 5.4-, 4.3- and 7.7-fold higher than the values in the chicks of the low-Se parents. When the offspring from the two parental groups were both maintained on the low-Se progeny diet, the tissue Se concentrations in chicks originating from the high-Se hens remained significantly higher for 3–4 weeks after hatching, compared with the values in chicks from the low-Se hens. Similarly, tissue glutathione peroxidase activity remained significantly higher in chicks from the high-Se hens for 2–4 weeks post-hatch. Thus, the effects of maternal Se supplementation persist in the progeny for several weeks after hatching. However, when chicks hatching from low-Se eggs were placed on a high Se diet, their tissue Se concentrations at 7 days of age were markedly higher than the values in chicks from high-Se eggs placed on the low-Se diet.     

Producing selenium-enriched eggs and meat to improve the selenium status of the general population

The role of selenium (Se) in human health and diseases has been discussed in detail in several recent reviews, with the main conclusion being that selenium deficiency is recognised as a global problem which urgently needs resolution. Since selenium content in plant-based food depends on its availability from soil, the level of this element in food and feeds varies among regions. In general, eggs and meat are considered to be good sources of selenium in human diet. When considering ways to improve human selenium intake, there are several potential options. These include direct supplementation, soil fertilisation and supplementation of food staples such as flour, and production of functional foods. Analysing recent publications related to functional food production, it is evident that selenium-enriched eggs can be used as an important delivery system of this trace mineral for humans. In particular, developments and commercialisation of organic forms of selenium have initiated a new era in the availability of selenium-enriched products. It has been shown that egg selenium content can easily be manipulated to give increased levels, especially when organic selenium is included in hen’s diet at levels that provide 0.3–0.5 mg/kg selenium in the feed. As a result, technology for the production of eggs delivering ≈50% (30–35 μg) of the human selenium RDA have been developed and successfully tested. Currently companies all over the world market selenium-enriched eggs including the UK, Ireland, Mexico, Columbia, Malaysia, Thailand, Australia, Turkey, Russia and the Ukraine. Prices for enriched eggs vary from country to country, typically being similar to free-range eggs. Selenium-enriched chicken, pork and beef can also be produced when using organic selenium in the diet of poultry and farm animals. The scientific, technological and other advantages and limitations of producing designer/modified eggs as functional foods are discussed in this review.     

The human selenium status in 27 regions of Russia.

Russia is the largest nation in the world and it has vastly different climatic and geochemical conditions. The human selenium status is determined mainly by the selenium intake from foods, whose concentration is subject to geochemical, geological and temporal factors. The data on the selenium status of populations in Russia are scarce and sporadic. This review presents the most recent selenium data acquired using adequate quality assurance measures. Serum samples were obtained from 2462 healthy blood donors between 1990-1996 from 125 locations representing 27 different regions of Russia. Samples of wheat flour and dried milk were also analyzed from most regions. The mean serum selenium concentration per region varied from 0.80 mumol/l in the western regions (Pskov) to 1.84 mumol/l in the easternmost regions (Sakhalin). A low (0.76-1.00 mumol/l) serum selenium concentration was found in only 6% of the locations. In 88% of the locations the mean serum selenium concentrations were moderate (1.01-1.40 mumol/l) and the highest values, > 1.45 mumol/l were found in eight towns. Wheat flour selenium concentrations varied widely from 44 to 557 micrograms/kg depending on the origin. The low values were either domestic or European and the high values of American or Australian origin. A high correlation between serum selenium and wheat flour (r = 0.79) suggests that the selenium status in most instances is determined by high selenium in wheat. Overtly very low or high serum selenium levels were not found in the 27 regions studied in Russia.     

The formation of status hierarchies in leaderless groups

Two studies examined the link between social dominance and male waist-to-hip ratio (WHR). Groups of four men interacted in a leaderless group discussion. In both studies, men with higher WHRs (associated with current and long-term health status) were rated by other group members as behaving more leader-like when an observer was present, and rated themselves as being more assertive. In Study 2, men with higher WHRs were rated by independent observers as behaving more dominantly, but only when the evaluator was present. These results are discussed in terms of evolutionary models of health, attraction, and intrasexual competition.     

Serum selenium levels in Slovak population

Blood serum selenium levels were measured in 576 healthy middle aged adults (40–60 yr, 255 men and 321 women) residing in both urban and rural areas in four districts of Slovakia. Serum selenium was determined by electrothermal AAS. The mean (±SD) serum selenium concentration was 0.852±0.335 μmol/L, ranging from 0.219–2.30 μmol/L. A large proportion of the individuals (19.62%) exhibited serum selenium levels under 0.57 μmol/L (45 μmol/L). There was no significant correlation between serum, selenium concentration and age, sex, and smoking status. There were significant differences between districts. The lowest mean (±SD) serum selenium was 0.664±0.269 μmol/L, the highest mean serum selenium (±SD) was 0.975±0.361 μmol/L. This differences could probably be attributed to the selenium, content in the soil of the different areas, which would contribute to the average daily selenium intake. In comparison with serum selenium levels in other European countries, the concentrations of selenium in the Slovak population are relatively low.     

Improvement of selenium status of pasture crops

Selenium was applied to pasture crops in a field experiment (1) by foliar application of 10 g Se/ha as selenite in the spring, (2) or by 5 g Se/ha in the spring plus 5 g in early August, (3) as selenite-enriched calcium ammonium nitrate (CAN) at 4 g Se/ha after each cut, and (4) as 4 g Se after every second cut. The experiment covered 2 yr. The results showed that applying 4 g Se in CAN/ha five times and spraying with 10 g Se/ha were efficient and safe measures to raise the average Se concentrations from about 0.04 ppm to 0.06-0.1 ppm. The yield of dry matter was lower in 1981 than in 1980 and consequently the Se concentrations were higher. Dividing the foliar application of 10 g Se/ha into two applications increased the efficiency considerably.     

The status of the Amboseli rhino population

The status of the Amboseli rhino population has given rise to particular concern, due to an apparently rapid decline since the 1950s. Information on the causes of death is available over the last 3-3 years and ground counts give a reasonable picture of the gross population structure of the rhinos. Aerial counts indicate a significant decline and provide population estimates on which a reconstruction of changes is possible. It is shown that the population has been declining at an average of about 12% per annum over the last 4 years at least. Seventy-five per cent of mortality results from spear wounds inflicted by Maasai. Natality is dropping rapidly, while the level of spearing is increasing. Spearing is possibly nonselective, so that the age-distribution may be similar to previous periods when the population was more stable. As a result, natality is probably not responding to increasing mortality. It is concluded that the rhino population is unable to effectively alter the magnitude of decline through intrinsic factors, or immigration. It would take a population over twice its present size to offset the impact of spearing. The effect of a rapidly changing environment is considered, but although it may result in slightly less favourable conditions for the rhinos, any decline is completely masked by spearing. The reasons for spearing and the recent increases are discussed, as well as the future prospects and implications.     

Generational differences in selenium status of women

In this cross-sectional study of three generations of women, daughters (19–26 yr), mothers (40–58 yr) and maternal grandmothers (67–84 yr) from the same 10 families in central Ohio were studied to determine the effect of life-cycle differences, including estrogen status, on selenium status. Plasma and red blood cell (RBC) selenium and glutathione peroxidase (GPx) activities were determined and typical dietary selenium intakes were calculated from food-frequency questionnaires. Selenium status was lowest in the oldest generation. Plasma selenium of daughters and grandmothers were significantly lower than those of mothers, and plasma GPx and RBC selenium of grandmothers were also lower than those of the mothers. A positive correlation (r=0.42, p<0.04) was found between plasma estrogen and plasma selenium concentrations. Selenium intakes of all groups were adequate and no differences in selenium intakes were found among groups. The results of this study indicate that selenium status fluctuates during the female life cycle and is related to estrogen status.     

Considerations on the assessment of selenium status

There is increasing interest in the techniques available for assessing Se status because of the accumulating evidence from laboratory animal experiments and human epidemiological studies that suggests a link between Se and the incidence of certain types of human cancer. In this paper, different methods of Se assessment are described, including analytical approaches (dietary intakes, tissue contents, and excreta levels), functional biochemical measurements (glutathione peroxidase activity), and functional physiological tests. The importance of considering interacting nutrients and other interacting substances is pointed out. Typical values of some Se status indicators reported in normal, deficient, and selenotic states are given.     

Postnuptial moult in a Belgian population of Nuthatches Sitta europaca

Postnuptial moult was studied in three consecutive years in a small population of Nuthatches. Fourteen to 25 individuals were captured in active moult each year with an average of 2.1 captures per bird per season. The total duration of moult was estimated as 88 days. Secondary moult was completed a few days after the end of primary moult. Primary moult rate was maximal at the beginning of moult, because many feathers were then growing simultaneously. Individual differences in the timing of moult were small, with a maximal spread of 21 days, and there was little variation between years. No differences in moult were found between sexes or age classes. Birds with failed broods moulted before successful breeders and early breeding females before late breeders. Duration and timing of moult are compared with other resident passerine species. A hypothesis based on summer territorial behaviour is put forward to explain the high degree of synchronization within the population and the relation between breeding and moulting.     

Effects of long-term selenium yeast supplementation on selenium status studied in the rat

To investigate the selenium status during long-term dietary supply of selenium yeast, 30-day-old male rats were fed for 379 days a methionine-adequate low-selenium diet supplemented with 0.2 mg Se/kg (selenium-adequate diet) or 1.5 mg Se/kg (high-selenium diet) in the form of selenium yeast that contained 60% of the element as l-selenomethionine. Their selenium load was determined at several intervals by neutron activation analysis of the selenium concentrations in the main selenium body pools, skeletal muscle and liver. After 64 days the tissue selenium concentrations plateaued in both groups and then stayed at that level. Compared with the selenium-adequate group, elevated tissue selenium concentrations were found in the high-selenium group, but the increase by a factor of 3.5 in the muscle and by a factor of 2.3 in the liver was smaller than the 7.5-fold increase in the selenium intake. In the selenium-adequate group about 50% of the muscle selenium and 30% of the liver selenium and in the high-selenium group about 85% of the muscle selenium and 70% of the liver selenium were estimated to be present in non-selenoprotein forms. During selenium depletion the liver glutathione peroxidase activity in the high-selenium group remained unaffected for 4 weeks and then decreased more slowly than that in the selenium-adequate group. From these results it can be concluded that selenium incorporated from the selenium yeast diet into non-selenoprotein forms can serve as an endogenous selenium source to maintain selenoprotein levels in periods of insufficient selenium supply.     

Urine selenium level in healthy adult population

The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium.     

Effects of selenium supplementation on selenium status of farmed fallow deer in outdoor pens

The study investigated the effects of selenium (Se) supplementation on Se status in farmed fallow deer. Fallow deer were housed on grass pasture and adapted to consume ∼200 g of pelleted grain daily. Animals were divided into two groups. One group received pelleted grain enriched with sodium selenate for 12 weeks (Se+ group, N = 10). Se intake for the first 7 weeks was 0.18 mg/kg dry matter (DM) and 0.32 mg/kg DM for the subsequent 5 weeks. The control group was fed pelleted grain without extra Se (Se− group, N = 9, 0.06-0.08 mg/kg DM). Blood samples were collected at the beginning and the end of the experiment. After the animals were slaughtered, tissue samples were collected for analysis of Se concentrations and Se-dependent glutathione peroxidase 1 (GPx1) activity. In addition, Se-independent α-glutathione-S-transferase (α-GST) activity was analyzed in liver tissue. Se supplementation significantly increased Se levels in plasma and in tissues as follows: liver > spleen > skeletal muscle > myocardium > kidney. Se supplementation also significantly increased GPx1 activity in tissues in the following order: liver > skeletal muscle > spleen = myocardium > kidneys. However, hepatic α-GST activity did not differ between Se+ and Se− groups. As expected, Se supplementation increased blood and tissue Se concentrations and GPx1 activity, which suggests a better antioxidant status. However, the activity of α-GST, an important Se-independent antioxidant enzyme, was not altered, presumably because GPx provided an adequate antioxidant capacity even though Se intake was low.     

The gastrointestinal microbiota affects the selenium status and selenoprotein expression in mice

Colonization of germ-free (GF) mice has been shown to induce the gastrointestinal form of the selenium-dependent glutathione peroxidases, GPx2. Since bacterial colonization of the gastrointestinal tract is associated with stress, we aimed to clarify how bacteria affect selenoprotein expression in unstressed conditions. GF and conventional (CV) FVB/NHan(TMHsd) mice were fed a selenium-poor (0.086 ppm) or a selenium-adequate (0.15 ppm) diet for 5 weeks starting from weaning. Each group consisted of five animals. Specific glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) expression was measured in plasma, liver and intestinal sections by activity, protein and mRNA level as appropriate. Under selenium-adequate conditions, selenoprotein expression did not differ in GF and CV mice. Under selenium-limiting conditions, however, GF mice generally contained higher GPx and TrxR activities in the intestine and liver, higher GPx1 protein and RNA levels in the liver, higher GPx2 protein levels in the proximal and distal jejunum and colon and higher GPx1 and GPx2 RNA levels in the colon. In addition, higher selenium concentrations were estimated in plasma, liver and cecum. All differences were significant. It is concluded that bacteria may compete with the host for selenium when availability becomes limiting. A variable association with different microorganisms might influence the daily requirement of mice for selenium. Whether the microbiota also affects the human selenoprotein status appears worthy of investigation.     

The effects of organic selenium supplementation on the rumen ciliate population in sheep

The effect of selenium supplementation on the rumen protozoan population of sheep was demonstrated. Both the total and generic counts of rumen ciliates in sheep fed a diet with basal Se content (70 microg/kg dry matter) were compared to those of animals given feed supplemented with inorganic (disodium selenite) or organic Se (selenized yeast) (310 microg/kg dry matter). The genera of Entodinium, Isotricha, Dasytricha, Ophryoscolex, Diploplastron and Polyplastron occurred in all sheep except for the control, in which Ophryoscolex was not observed. The population of Ophryoscolex caudatus f. tricoronatus was significantly higher in sheep supplemented with organic Se than in animals given inorganic Se (by 160 %). Supplementation of feed with selenized yeast induced significant growth in the Diploplastron population (by 63 %) while no change occurred in sheep given selenite. The populations of Dasytricha ruminantium and Polyplastron multivesiculatum were higher than control in both Se-supplemented groups. The ciliate population of Entodinium spp. was not influenced by Se supplements. Our results suggest a protective effect of Se feed supplementation on the development of some rumen ciliate species in young ruminants.