Milk Se Research Articles

Dose-response effects of long-acting injectable vitamin B12 plus selenium (Se) on the vitamin B12 and Se status of ewes and their lambs

AIM: To determine the effect of increasing doses of long-acting injectable vitamin B12 plus selenium (Se) given pre-mating on the vitamin B12 and Se status of ewes and their lambs from birth to weaning. METHODS: Four groups of 24 Poll Dorset ewes each were injected 4 weeks pre-mating with different doses of a long-acting vitamin B12 + Se product, containing 3 mg vitamin B12 and 12 mg Se per ml. The treatment groups received 5 ml (15 mg vitamin B12 + 60 mg Se), 4 ml (12 mg vitamin B12 + 48 mg Se), 3 ml (9 mg vitamin B12 + 36 mg Se), or no vitamin B12 or Se (control). Twelve of the twin-bearing ewes per group were selected for the study. Efficacy of the product was evaluated from changes in the concentrations of vitamin B12 in serum and liver, and of Se in blood, liver and milk in the ewes during gestation and lactation, and in their lambs from birth to weaning. Pasture samples in paddocks grazed by the ewes and lambs were collected at about 2-monthly intervals from 200-m transects. RESULTS: The flock was Se-deficient, as the mean initial concentration of Se in the blood of ewes was 182 (SE 20.3) nmol/L. Compared with untreated controls, all doses significantly (p<0.01) increased concentrations of Se in the blood of ewes for at least 300 days. Selenium concentrations in milk were likewise increased throughout lactation, as were those in the blood and liver of lambs. The mean concentration of vitamin B12 in the serum of ewes was initially > 1,000 pmol/L, but this decreased within 28 days to <460 pmol/L. Treatment with the 5-ml and 4-ml doses raised serum vitamin B12 concentrations of ewes for at least 176 days (p<0.01), while their lambs had significantly greater concentrations of vitamin B12 in serum and liver for less than 37 days after birth. Tissue concentrations and duration of elevation of both vitamin B12 and Se were proportional to the dose administered. The mean concentrations of Se and cobalt (Co) in the pastures were 32 and 74 µg/kg dry matter (DM), respectively. CONCLUSIONS: Injecting ewes from a Se-deficient flock 4 weeks prior to mating with 48 or 60 mg Se and 12 or 15 mg vitamin B12 increased and maintained the Se status of ewes for at least 300 days, and of their lambs from birth to weaning. The vitamin B12 status of ewes was increased for at least 176 days and that of their lambs for less than 37 days. Due to the proportional nature of the response to increasing dosage, the dose rate of the formulation tested can be adjusted according to the severity of Se and Co deficiency in a flock. CLINICAL SIGNIFICANCE: A single subcutaneous injection of vitamin B12 + Se administered pre-mating to Se-deficient flocks is likely to prevent Se deficiency in ewes and their lambs until weaning, as well as increase the vitamin B12 status of ewes and their lambs until 5 weeks after lambing.

Effect of Selenium Source on Selenium Status, Neutrophil Function, and Response to Intramammary Endotoxin Challenge of Dairy Cows

The effects of feeding dry and early lactation dairy cows diets with selenate or selenized yeast (Se-yeast) on concentrations of Se in serum, milk, and newborn calves, neutrophil function, and inflammatory response were determined. At 60 d before anticipated calving until approximately 30 d in milk (DIM), cows were fed diets that contained 0.3mg of supplemental Se/kg of DM from sodium selenate or Se-yeast. Diets also contained 0.2% supplemental S (as sulfate) because it has been shown to reduce absorption of Se by dairy cows. The concentration of Se in serum at calving and 28 DIM was about 1.4 times greater for cows fed Se-yeast than for those fed selenate. Serum concentrations decreased 45 and 23% from dry-off to calving for cows fed selenate or Se-yeast, respectively. Selenium concentrations in serum from newborn calves were also about 1.4 times greater when the dams were fed Se-yeast. Concentrations of Se in colostrum and milk were about 1.8 times greater when cows were fed Se-yeast. Blood neutrophils were isolated from cows at 28 DIM and were used in an in vitro kill assay. Selenium treatment did not affect bacterial kill or the percentage of neutrophils that phagocytized bacteria. At approximately 28 DIM, one quarter from each cow was infused with a solution containing endotoxin. Peak body temperature (40.7°C) occurred 6h postinfusion, and peak somatic cell count (6.5 log10/mL) occurred at 12h postinfusion. Neither measure was influenced by Se treatment.

Selenium Content and Distribution in Cow's Milk Supplemented with Two Dietary Selenium Sources

The effect of two sources of Se, selenized yeast (Se-Y) and sodium selenite, added to total mixed rations (TMR) fed to cows on Se milk content and distribution in milk components was studied on three farms for 6 weeks. The maximal increase in milk Se was attained with Se-Y supplemented at 0.3 microg g(-1). The effect was immediate, with an increase of 9 microg L(-1) being observed after only 5 days, and remained steady until the last sample at day 40 of Se supplementation. Se distribution in milk components was constant, 53.6, 42.6, and 9.3% in whey, casein, and fat, respectively, and was unaffected by the form of supplementation. The effect of the level of Se-Y supplementation on milk Se was studied on two farms. Increasing dietary Se-Y from 0 to 0.5 microg g(-1) elevated milk Se content from 20 to 39 microg L(-1). Se-enriched cow's milk at different levels can be produced by varying dietary Se supplementation in the form of selenized yeast.

Effects of selenium levels in ewe diets on selenium in milk and the plasma and tissue selenium concentrations of lambs

The objective of this 504 day experiment was to evaluate and compare the effects of six levels of dietary selenium (Se) on ewes’ milk and the Se status of their lambs prior to weaning. Sodium selenite was added to a basal diet to provide 0.2 (control), 4, 8, 12, 16, and 20 mg/kg dietary Se for ewes during gestation and lactation over two lambings. Colostrum Se ranged from 257 to 3542 μg/L and increased linearly as dietary Se increased ( P < 0.001) in both years. Ewe milk Se ranged from 75 to 2228 μg/L and also increased linearly as dietary Se increased ( P < 0.01). In general, ewes receiving >12 mg/kg Se produced higher milk Se than controls. Blood samples were collected from lambs before nursing and at 3, 28, and 56 days of age to evaluate plasma Se concentrations. At birth, lamb plasma Se ranged from 74 to 775 μg/L and was affected ( P < 0.001) by the Se concentration of the ewe diets, which indicates placental transfer of Se. Lambs from ewes receiving dietary Se at 20 mg/kg had higher ( P < 0.05) plasma Se than controls at birth and 3, 28, and 56 days of age in both years. Selenium concentration in lamb testes collected at 70 days of age was also affected by Se content of ewe diets. In year 1, lambs whose dams received 16 or 20 mg/kg Se had higher ( P < 0.05) testicular Se than controls, and no differences in testicular Se were observed in year 2. No signs of Se toxicosis were observed in lambs regardless of dietary Se concentration of the ewes’ diet. These results suggest that ewes consuming up to 20 mg/kg inorganic Se may give birth to normal lambs, and that the lambs may not suffer from Se toxicosis before weaning. Selenium as sodium selenite may be fed to ewes at concentrations greater than the current maximum tolerable levels (2 mg/kg) without adversely affecting their offspring.

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.

Fluorimetric study of the selenium course in the dam-calf relationship.

This study was conducted in a southeast region of Romania, known to be selenium (Se) deficient. The fluorimetric method for the determination of Se in biological samples was used in a study on the serum Se content in time in a group of 10 cows with a high milk yield and in their calves. The same cows were sampled antepartum (late pregnancy) and postpartum (1, 7, 21, 30, and 60 d), and the calves were sampled on d 1 of life and 7, 21, 30, and 60 d postcalving. Colostrum and milk samples were also collected and analyzed at the same times. Throughout the study, the serum Se content in both the cows and the calves was below the reference values (0.040-0.100 microg/mL), except the control conducted 7 d postpartum, for which it was 0.044 +/- 0.017 and 0.023 +/- 0.007 mg/mL in cows and calves, respectively. The most significant drops were recorded 21 (p<0.01) and 60 d postpartum (p<0.05). The colostrum Se was higher (0.036 +/- 0.022 microg/mL), decreasing progressively throughout the study to the normal low limit (0.005 microg/mL). The milk Se concentration was lower by approx 78% than the colostrum one on d 1 postcalving. These data demonstrate the course of hyposelenosis both in the cows and their calves. The maternal body proved to "mobilize," even in case of deficiency, important Se amounts in the colostrum, during the first days in particular.

Determination of As, Sb, Se, Te and Bi in milk by slurry sampling hydride generation atomic fluorescence spectrometry

A simple and fast analytical procedure has been developed for the determination of As, Sb, Se, Te and Bi in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS). Samples were treated with aqua regia for 10min in an ultrasound water bath and pre-reduced with KBr for total Se and Te determination or with KI and ascorbic acid for total As and Sb, the determination of Bi being possible in all with or without pre-reduction. Slurries of samples, in the presence of antifoam A, were treated with NaBH4 in HCl medium to obtain the corresponding hydrides, and AFS measurements were processed in front of external calibrations prepared and measured in the same way as samples. Results obtained by the developed procedure compare well with those found after microwave-assisted complete digestion of samples. The proposed method is simple and fast, and only 1ml of milk is needed. The values obtained for detection limit are 2.5, 1.6, 3, 6 and 7ngl−1 for As, Sb, Se, Te and Bi respectively in the diluted samples, with average relative standard deviation values of 3.8, 3.1, 1.9, 6.4 and 1.2% for three independent analysis of a series of commercially available samples of different origin. Data found in Spanish market samples varied from 3.2±0.3 to 11.3±0.2ngg−1 As, from 3.1±0.2 to 11.6±0.4ngg−1 Sb, from 10.7±0.5 to 25.5±0.4ngg−1 Se, from 0.9±0.2 to 9.4±0.6ngg−1 Te and from 11.5±0.1 to 27.7±0.4ngg−1 Bi.

Direct determination of iron and selenium in bovine milk by graphite furnace atomic absorption spectrometry

Milk is a complex sample containing high contents of organic compounds and its analysis generally involves digestion procedures that can be affected by losses and contamination. In the work here described it was developed a procedure for determination of Fe and Se in bovine milk. Samples were diluted using a mixture of water-soluble tertiary amines (10% v/v CFA-C). The tertiary amines had a favorable effect on the action of the autosampler and consequently on repeatability. Using this strategy the direct analysis of milk without any digestion procedure by graphite furnace atomic absorption spectrometry is feasible. Pyrolytic graphite tubes were used and all measurements were based on peak area of transient signals with background signal correction based on Zeeman effect. Palladium was used as chemical modifier for Se. The pyrolysis and atomization temperatures were 1300 and 2300 °C for Fe and 1500 and 2400 °C for Se, respectively. The procedure was applied for 13 bovine milk samples from different sources. The quantification was based on the standard additions method. The lifetime of the graphite tube was 300 and 250 heating cycles for Fe and Se, respectively.

Selenium and breast-feeding.

The objective of the present review is to discuss Se nutrition during breast-feeding, encompassing environmental and maternal constitutional factors affecting breast-milk-Se metabolism and secretion. A literature search of Medline and Webofscience was used to retrieve and select papers dealing with Se and breast milk. Although Se in natural foods occurs only in organic form, breast milk responds to organic and inorganic Se in supplements. Inorganic Se (selenite, selenate), which is largely used in maternal supplements, is not detectable in breast milk. The mammary-gland regulating mechanism controls the synthesis and secretion of seleno-compounds throughout lactation, with a high total Se level in colostrum that decreases as lactation progresses. Se appears in breast milk as a component of specific seleno-proteins and seleno-amino-acids in milk proteins that are well tolerated by breast-fed infants even in high amounts. Se in breast milk occurs as glutathione peroxidase (4-32 % total Se) > selenocystamine > selenocystine > selenomethionine. The wide range of breast-milk Se concentrations depends on Se consumed in natural foods, which reflects the Se content of the soils where they are grown. Se prophylaxis, either through soil Se fertilization or maternal supplements, is effective in raising breast-milk Se concentration. In spite of wide variation, the median Se concentration from studies worldwide are 26, 18, 15, and 17 microg/l in colostrum (0-5 d), transitional milk (6-21 d), mature milk (1-3 months) and late lactation (>5 months) respectively. Se recommendations for infants are presently not achieved in 30 % of the reported breast-milk Se concentrations; nevertheless Se status is greater in breast-fed than in formula-fed infants.

MINERAL CONTENT IN GOATS' MILKS

AbstractConcentrations of eight essential minerals were determined in 78 samples of goats'milk from the Canary Islands. The following mean values (ranges) were found: Se (μ/L), 19.98 (9.2‐31.2); Fe (mg/L), 0.52 (0.19‐1.17); Cu (mg/L), 0.17 (0.08‐0.31); Zn (mg/L), 3.31 (1.6‐4.6); Na (mg/L), 514 (289‐906); K (mg/L), 1585 (1212‐2160); Ca (mg/L), 1533 (1118‐1962); and Mg (mg/L), 157 (101‐210). Comparing with data for human milk and cows' milk from the Canary Islands, the mean concentrations of Se, K and Mg arranged in according the following sequence: goats' milk &gt; cows' milk &gt; human milk. Cows' milk had the highest (P&lt;0.05) mean concentration for Ca and Zn, while humans had the highest (P &lt; 0.05) mean concentration for Cu. The milk of goats milked once per day had significantly higher concentrations of Se and lower Mg and Zn than the milk of goats milked twice per day. While the concentrations of Na and Mg increased significantly from March to August, the concentrations of Se, Fe and Cu in goats' milk decreased significantly from March to June.

Milk selenium content is enhanced by modest selenium supplementation in extended lactation

AbstractSupplemental selenium (Se) as selenate, selenomethionine, or Se‐enriched yeast at 100–200 μg Se/day causes an increase or prevents a decline in human milk selenium content during the first 6 months of lactation. In this study, we evaluated the impact of supplemental Se as sodium selenate at 20 μg/day, an amount that closely approximates the quantity of selenium lost daily via milk secretion. Lactating women (n = 23) provided dietary data and milk and plasma samples at 3 and 6 months postpartum. At 3 months postpartum, all women received a daily vitamin/mineral supplement that furnished 20 μg of Se as sodium selenate for 3 months. Mean Se intake from self‐selected diets was 111 ± 40 μg/day and did not differ between 3 and 6 months. Selenium supplementation increased milk Se from 3 (295 ± 18 nmol/L; 23 ± 7 ng/mL) to 6 months (417 ± 39 nmol/L; 32 ± 14 ng/mL) postpartum (P ≤ 0.01) and corresponding infant Se intakes from 12 μg/day to 20 μg/day. Maternal plasma Se concentration was 1.46 ± 0.42 μmol/L (115 ± 33 ng/mL) at 3 months and 1.76 ± 0.20 μmol/L (155 ± 16 ng/mL) at 6 months postpartum, but this apparent difference was not significantly different. Maternal supplemental Se at 20 μg/day caused a 41% increase in human milk Se and a corresponding 67% increase in infant Se intake. Data show that supplemental Se at or near the quantity secreted daily is sufficient to prevent a decline in human milk Se with advancing lactation. J. Trace Elem. Exp. Med. 15:191–199, 2002. © 2002 Wiley‐Liss, Inc.

The potential of double focusing-ICP-MS for studying elemental distribution patterns in whole milk, skimmed milk and milk whey of different milks

The aim of this work was to investigate the potential of DF-ICP-MS for studying in a straightforward manner multielemental distribution patterns in human, cow and formula milks. Thus, the multielemental determination of essential and toxic elements, of primary importance, such as Na, Ca, Mg, Al, Cr, Mn, Fe, Ni, Cu, Zn, Se, Sr, Cd, Hg and Pb in whole milk, skimmed milk and milk whey by DF-ICP-MS is described. Skimmed milk and milk whey were obtained from whole milk by means of physical procedures (ultracentrifugation), without any chemical treatment. In order to destroy organic matrix, each sample was digested (before ICP-MS final analysis) by using a microwave assisted digestion method. A reference material, BCR natural skim milk powder (CRM 063) was analysed for testing the accuracy of the proposed methodology. After validation, the method has been applied to the multielemental analysis of different milk types and fractions. Results of total concentrations and distribution patterns of the above-mentioned elements in the different fractions (whole milk, skimmed milk and milk whey) of human milk, cow milk and formula milk, are presented.

Relationship between blood selenium concentration or glutathione peroxidase activity, and milk selenium concentrations in New Zealand dairy cows

Aim: To determine the relationships between blood selenium (Se) concentrations or glutathione peroxidase activity (GSH-Px), and milk Se concentrations in dairy cows. Methods: Seventy-two Friesian dairy cows were either untreated or injected with 0.5, 1.0 or 2.0 mg Se/kg liveweight as barium selenate (BaSeO4) formulations, resulting in 6 groups of animals with mean blood Se concentrations that varied from 212 to 2272 nmol/l. Milk samples were collected on Days 104 and 188, and blood samples were collected prior to treatment and on Days 41, 76, 104, 188, 244, and 292 after Se injection. Results: Significant quadratic relationships between blood Se and milk Se concentrations, as well as blood GSH-Px activity and milk Se concentrations, were evident at Days 104 and 188. Using combined data, these were represented by the equations: milk Se = 27.3 + 0.073 blood Se -0.00001 (blood Se)2; R2=0.79, p<0.005, and; milk Se = 34.8 + 4.99 GSH-Px -0.068 (GSHPx)2; R2=0.79, p<0.005. Conclusions: The Se status of dairy cows can be assessed from milk Se concentrations. Clinical significance: Bulk-tank milk Se concentrations could be evaluated as a method to assess the Se status of dairy herds.

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.

Significance of Amount and Form of Dietary Selenium on Blood, Milk, and Casein Selenium Concentrations in Grazing Cows

Organic selenized yeast enriched with selenoamino acids or inorganic sodium selenate (Na2SeO4) was administered per os three times weekly as a drench for 133 d to previously unsupplemented cows that were grazing low Se pastures. Treatment groups received the equivalent of 2 or 4 mg of Se/d of either supplement form. Control cows did not receive a drench. Samples of blood and milk were collected regularly throughout the trial. Selenium concentrations in blood, milk, casein, and liver and glutathione peroxidase activity in blood and liver are reported as responses per milligram of Se intake. Mean blood Se concentrations in treated cows increased steadily and, by d 133, were 4.7 to 8.8 times that in controls. Selenized yeast was 2 to 3 times more effective than was Na2SeO4, and low Se intakes were 27% more efficient per milligram of Se administered than were high Se intakes at increasing milk Se concentration. Casein Se content mirrored that of milk; among all treated and control cows and throughout the trial, the molar ratio of Se in casein as a percentage of the Se in whole milk was constant at 71 +/- 1.2%. The Se concentration in liver biopsies taken on d 133 was indicative of total Se intake during the trial and ranged from 920 to 3920 nmol of Se/kg of fresh weight. These results demonstrate the differing efficacy of organic and inorganic Se dietary supplements to increase dairy cow Se status and to enhance Se content of milk and casein.

The influence of dietary selenium as selenium yeast or sodium selenite on the concentration of selenium in the milk of Suckler cows and on the selenium status of their calves.

The aim of this trial was to determine whether the selenium status of suckling calves could be improved by supplementing their dams' diet with organic Se instead of sodium selenite. A herd of 103 Hereford cows, which were on grass paddocks all year round, was divided into two groups. Both groups had free access to a mineral supplement that contained 30 mg of Se/kg; for one group the source of the Se was a Se yeast product, and for the other group the source was sodium selenite. The basal feed contained .02 mg of Se/kg DM. During the trial, the mean daily consumption of the mineral supplement was approximately 110 g/cow. The calving season started in the middle of March and ended in the middle of May. Blood samples were taken from 11 cows and their calves in the yeast group and from nine in the selenite group at the end of April and again at the beginning of June, and milk samples were taken at the same times. At both samplings, the concentration of Se in whole blood and the activity of glutathione peroxidase (GSH-Px) in the erythrocytes of the cows and calves in the yeast group were higher than in the samples from the animals in the selenite group. The same pattern was seen for plasma, except for the cows at the first sampling. The mean concentrations of Se in whole blood from calves in the yeast and selenite groups were 130 and 84 microg/L, respectively, and plasma concentrations were 48 and 34 microg/ L, respectively. Mean Se concentration in the milk from the yeast group (17.3 microg/L) was higher than that in milk from the selenite group (12.7 microg/L). There were significant correlations (r = .59 to .68) between the concentrations of Se in the cow's milk or cow's whole blood compared with Se concentrations in the calves whole blood and plasma or with the erythrocyte GSH-Px activity of the calves. The Se status of the calves in the selenite group was considered to be marginal, but the status of the calves in the yeast group was considered to be adequate. Supplementation of the suckler cows' diet with organic Se in the form of Se yeast rather than sodium selenite improved the Se status of their calves when the Se was mixed into a mineral supplement containing 30 mg of Se/kg. In practice, such supplementation would probably eliminate the risk of nutritional muscular degeneration in suckling calves.

Concentrations of selenium in human milk

Selenium (Se) concentrations in 58 samples of mature human milk from Canarian women were determined by spectrofluorimetry. According to the literature the Se concentrations found fall within the normal limits. The concentration of Se in human milk was compared with that in powdered infant formula and presented significantly lower concentrations in the latter. Babies fed with human milk had an adequate intake of Se. However, babies fed with powdered infant formula consumed only 56% of the requirements recommended by The National Research Council. No changes in Se concentration were observed between lactation stages. Human milk produced in springtime was found to be richer in Se than that produced in the autumn, which could be due to changes in the nutritional habits of the mothers. The mother's age, weight, height and number of previous children were not found to influence the Se levels in the milk.

Organic and Inorganic Selenium Supplementation to Lactating Mothers Increase the Blood and Milk Se Concentrations and Se Intake by Breast-fed Infants

The aim of this study was to determine the effect of selenium (Se) supplementation to lactating women on Se concentrations and glutathione peroxidase (GSH-Px) activities in blood components of mothers and breast-fed infants and on milk Se levels and Se intake by breast-fed infants. Lactating mothers were supplied for 3 months with 200 micrograms Se/day in the form of yeast-Se (Y-Se) and sodium selenite. Initial blood and plasma Se levels of all women (n = 67) were 76.6 and 53.2 micrograms/L, respectively. After 3 months Se concentrations both in whole blood and in plasma from mothers and infants were significantly higher than the initial values. Y-Se exerts a stronger effects than selenite on blood and plasma Se levels. Initial milk Se concentration was 8.9 micrograms/L and after 1 month in both groups in reached a plateau at 14-16 micrograms/L. This resulted in an increase of Se intake in breast-fed infants from 6.1 to a plateau of 11-13 micrograms Se/day. GSH-Px activities in plasma and red cells of Y-Se group increased significantly and reached a plateau after 1 and 2 months, respectively, while in the selenite group the enzyme activities increased steadily throughout the entire period of the study. Selenite exerts a stronger effect on GSH-Px both in maternal and in infant blood components as compared with Y-Se. In milk the GSH-Px activity in the Y-Se group did not change during the study, while in the selenite group after 3 months it increased almost 2-fold compared to the initial value. In conclusion, this study shows that organic Se causes higher Se deposition than did the inorganic form.

Influence of Se status on milk Se concentrations in dairy cows

Changes in blood and milk selenium (Se) concentrations were measured in dairy cattle grazing Se‐deficient pastures compared with animals grazing the same pasture but given either an intraruminal Se bolus or a barium selenate injection. The Se supplementation significantly increased and maintained the blood Se concentrations (e.g., 342 versus 1113 nmol/1) over 190–265 days during the lactation and also increased milk Se concentrations 2‐fold (e.g., 77.2 versus 132.3 nmol/1).

Maternal Selenium Status Influences the Concentration and Binding Pattern of Zinc in Human Milk

To study the health effects of high dietary maternal selenium intake breast milk, blood and toe-nails were collected from 143 women (20-24 days of lactation) living in Venezuelan states of Yaracuy and Portuguesa. Depending on the regional selenium intake level three regions were defined within the total range of 90-980 microgram per day. The samples were analyzed by means of INAA for the determination of trace elements, including selenium and zinc. The significant inverse correlation between Se and Zn in breast milk found in former studies was confirmed. Investigation of the Zn-binding pattern in milk whey was carried out by an on-line combination HPLC (SEC) for protein separation and ICP-AES for element detection. Six Zn-binding compounds including citrate were detected. A highly significant negative correlation was found between the citrate, which is the main low-molecular Zn-binding compound, and the maternal daily selenium intake. We determined that the decrease in zinc concentration is due to a decrease in the citrate level, which depends on the selenium concentration in breast milk. The selenium concentration in breast milk is, in turn, proportional to the dietary intake. In addition, significant changes in the UV- and Zn-profiles were observed in the milk whey with the highest selenium content, indicating that above a certain maternal intake level substantial changes in the composition of mammary secretory cells occur. This effect can be of interest for estimation of the safe dietary intake level of selenium.