Enhancement of ovine lymphocyte responses: a comparison of selenium and vitamin E supplementation

Lymphocytes of lambs on a low selenium/vitamin E diet were isolated from peripheral blood, and mitogenic responses to phytohaemagglutinin (PHA) tested in the presence of different doses of sodium selenite and emulsified vitamin E added in vitro. An enhancing effect of selenium was observed at doses of 1 ng/ml or less, and reached a plateau at about 10 ng/ml. Toxic effects were evident beyond 1 micrograms/ml. The stimulatory potential of selenium among lambs was inversely related to their ability to respond to PHA in control cultures but was not related to the blood glutathione peroxidase activity of the animals concerned. Optimal doses of vitamin E added to culture (0.15-1.5 micrograms/ml) elevated responses beyond those seen with selenium, but synergistic effects were not apparent. Similar results were obtained when lymphocytes from deficient, myopathic lambs were cultured with serum from lambs supplemented in vivo, and when PHA responses of untreated and treated lambs were compared. Tests with other phytolectins (concanavalin A and pokeweed mitogen) suggested that the two micronutrients exert a differential influence on lymphocyte sub-populations. It was also concluded that the poor lymphocyte responses seen in myopathic lambs can be readily and rapidly reversed by injection of these nutrients, and that prophylaxis is most effective during the first 6 weeks of life.     

The effect of different levels of selenium in mineral mixtures and salt licks on selenium status in sheep

This paper describes 3 experiments comparing the effect of 10, 25 and 40 mg Se/kg, as sodium selenite, in mineral mixtures and salt licks fed to sheep. The supplement was given during the indoor season from October to May to 7 different flocks, each consisting of 50 to 100 sheep, in areas with selenium deficiency problems. The average selenium level in the basic diets did not exceed 0.05 mg/kg. Selenium status was monitored in the blood of ewes and lambs, and in milk. Blood selenium in lambs correlated well with blood selenium in their dams (r = 0.85). Selenium levels in milk on day 1 (colostrum) correlated well with selenium levels in dams (r = 0.92) and in offspring (r = 0.87). Statistically significant differences were found between the different flocks. In areas with extreme selenium deficiency, 10 mg Se/kg in mineral mixtures and salt licks proved insufficient. A content of 25 mg Se/kg, providing a daily intake of about 0.4 mg selenium, resulted in selenium levels in ewes’ blood, ewes’ milk and in the offspring that should prevent selenium deficiency disease without causing any toxic effects.     

Barium selenate: a long-acting selenium preparation for subcutaneous injection

Three flocks of sheep in typical selenium-deficient areas were injected with 2 ml Deposel® (100 mg selenium as barium selenate) in the autumn of 1982 and/or 1983. The selenium status in 10 ewes from each flock, and their offspring, was monitored by selenium analyses of blood samples. The injection induced an adequate increase in blood selenium within 8 weeks. Adequate selenium levels were maintained throughout the lambing season and the following summer. The selenium status in lambs from treated ewes was adequate until they were put out to pasture. Elevated selenium levels were maintained even throughout the next lambing season, and the second injection gave significantly higher blood selenium as compared to the first. The present preparation seems to be suitable and safe for protecting sheep against selenium deficiency. The dosage used seems sufficient to maintain an adequate selenium status for as long as 2 consecutive lambing seasons.     

Relationship between selenium content of forage, blood and organs of sheep, and lamb mortality rate

The investigation comprised 12 herds, totalling 660 sheep, in the counties of Stockholm and Uppsala. The selenium content of specimens of forage, whole blood, muscle, liver, and kidney was determined by a fluorimetric method. Data on the number of born and dead lambs were collected 4—5 months after lambing. Dead and sick lambs were subjected to necropsy and to clinico-chemical analyses, respectively.The selenium content of hay and corn was lower than 60 ng per g, which some authors regard as the minimum level of Se requirement for protection against white muscle disease in sheep. The analyses of forage mixtures containing oil concentrates and beet pulp showed selenium levels that were about 2—5 times as high as this minimum level.In herds in which the animals had not been treated with selenium preparations prior to sampling, there was a significant positive correlation between the selenium content of the forage and that of whole blood. A relationship was also noted between the selenium content of forage and of organs.In 9 out of the 12 herds the selenium concentrations in whole blood were on the level that is considered to be representative of white muscle disease.A high mortality rate was recorded for lambs whose mothers had low selenium levels in their blood.Prophylactic and curative treatment with selenium plus vitamin E orally and/or parenterally probably reduced lamb mortality rate in the herds fed a low-selenium diet.     

Organic selenium supplementation increased selenium concentrations in ewe and newborn lamb blood and in slaughter lamb meat compared to inorganic selenium supplementation

Background

Selenium is part of the antioxidant defence system in animals and humans. The available selenium concentration in soil is low in many regions of the world. The purpose of this study was to evaluate the effect of organic versus inorganic selenium supplementation on selenium status of ewes, their lambs, and slaughter lambs.

Methods

Ewes on four organic farms were allocated five or six to 18 pens. The ewes were given either 20 mg/kg inorganic selenium as sodium selenite or organic selenium as selenized nonviable yeast supplementation for the two last months of pregnancy. Stipulated selenium concentrations in the rations were below 0.40 mg/kg dry matter. In addition 20 male lambs were given supplements from November until they were slaughtered in March. Silage, hay, concentrates, and individual ewe blood samples were taken before and after the mineral supplementation period, and blood samples were taken from the newborn lambs. Blood samples from ewes and lambs in the same pens were pooled. Muscle samples were taken from slaughter lambs in March. Selenium concentrations were determined by atomic absorption spectrometry with a hydride generator system. In the ANOVA model, selenium concentration was the continuous response variable, and selenium source and farm were the nominal effect variables. Two-sample t-test was used to compare selenium concentrations in muscle samples from the slaughtered lambs that received either organic or inorganic selenium supplements.

Results

In all ewe pens the whole blood selenium concentrations increased during the experimental period. In addition, ewe pens that received organic selenium had significantly higher whole blood selenium concentrations (mean 0.28 μg/g) than ewe pens that received inorganic selenium (mean 0.24 μg/g). Most prominent, however, was the difference in their lambs; whole blood mean selenium concentration in lambs from mothers that received organic selenium (mean 0.27 μg/g) was 30% higher than in lambs from mothers that received inorganic selenium (mean 0.21 μg/g). Slaughter lambs that received organic selenium had 50% higher meat selenium concentrations (mean 0.12 mg/kg wet weight) than lambs that received inorganic selenium (mean 0.08 mg/kg wet weight).

Conclusion

Organic selenium supplementation gave higher selenium concentration in ewe and newborn lamb blood and slaughter lamb meat than inorganic selenium supplementation.     

The effect of copper on the response of lambs to selenium supplementation when grazing a selenium deficient pasture

Two trials were undertaken with lambs grazing selenium deficient pasture to determine if copper would enhance liveweight and fleece-weight responses to selenium supplementation. In the first trial, lambs given selenium or selenium plus copper gained significantly more weight and had higher fleece-weights after 260 days than did control lambs or lambs given copper alone. Copper given alone or together with selenium had no significant effect on liveweight or fleece-weight when compared with control lambs and lambs that were given selenium alone respectively. This finding was confirmed in a second trial when growth and fleece-weights of selenium and selenium plus copper treated lambs were compared and no significant differences found. In both trials copper significantly raised liver copper levels. In selenium supplemented but not in selenium deficient sheep, copper significantly increased blood selenium levels.     

Seasonal variation of selenium status of Norwegian dairy cows and effects of selenium supplementation

Blood selenium levels were found to fluctuate throughout the year, being highest during the indoor season when the greatest amounts of compound concentrates were fed. From October to January the average blood selenium levels increased from 0.10 μg/ml to 0.18 μg/ml (15 cows). Subcutaneous injections of barium selenate (500 mg selenium) increased the blood selenium levels significantly. The treated group (15 cows) reached average levels of about 0.21 μg/ml blood during the indoor season.The effect of oral supplementation of sodium selenite (for 2 months) on the levels of plasma selenium, blood selenium and glutathione peroxidase activity was investigated. Plasma selenium was found to give an immediate reflection of the daily selenium intake. Maximum activity of glutathione peroxidase was reached 1 month after the end of the supplementation period.It is concluded that if selenium enriched concentrates are used in a normal feeding regimen, further supplementation with selenium does not seem to be necessary.     

The application of a selenium fertiliser for the correction of marginal deficiencies in grazing sheep

A commercial fertiliser, consisting of a poorly soluble barium selenate core with a coating of highly soluble sodium selenite, was evaluated in 2 trials for the provision of selenium (Se) to grazing sheep. The fertiliser was administered at a level of 1 kg per hectare to 3 of 6 kikuyu paddocks during 1995 and 1996 in Trial 1, while the other paddocks were left untreated. The Se status of SA mutton merino ram lambs, as reflected by whole blood, liver and kidney Se concentrations, was elevated (P < 0.01) for at least 5 months after application of the fertiliser. Whole blood and liver Se concentrations of animals grazing unfertilised control paddocks were indicative of a subclinical Se deficiency at times (<100 ng Se/ml whole blood and <300 microg Se/kg liver dry matter). In Trial 2, 4 of 7 paddocks on which an oat fodder crop was established were treated with the Se fertiliser during 1995 and 1997. The remaining 3 paddocks were left unfertilised as controls. Groups of 10-15 pregnant SA mutton merino ewes were introduced to these paddocks within 2 weeks of parturition. These ewes and their progeny utilised these paddocks for a mean (+/- SD) period of 41 +/- 8 days after parturition. The whole blood Se concentrations of these ewes and their offspring were elevated (P < 0.01) relative to their contemporaries utilising control paddocks. No suggestion of a subclinical Se deficiency was discernible in animals grazing control paddocks, although whole blood Se levels approached 100 ng Se/ml during 1997. The application of Se fertiliser did not result in improvements in ewe reproduction or lamb growth. There was a suggestion of an improvement (P = 0.21) in mean (+/- SE) lamb survival on paddocks receiving Se fertiliser compared to control paddocks (71.5 +/- 4.6% vs 62.2 +/- 5.3% respectively).     

The biological selenium status of livestock in Britain as indicated by sheep erythrocyte glutathione peroxidase activity.

The reliability of erythrocyte glutathione peroxidase activity as an indicator of selenium status in livestock is discussed. Based on this measurement, a survey is described of the biological selenium status of sheep on each of 329 farms in Britain. Results showed that 47 per cent of these farms were probably unable to provide grazing livestock with sufficient selenium to maintain blood levels greater than 0.075 microgram per ml. Increased selenium deficiency from the increasing use of home grown feeds as a major constituent of livestock rations may be causally related to the increase of white muscle disease and other selenium responsive diseases in Britain.     

Studies on serum tocopherol, selenium levels and blood glutathione peroxidase activities in calves with white muscle disease

For the purpose of clarifying the cause of white muscle disease (WMD) in calves, tocopherol and selenium levels and blood glutathione peroxidase (GSH-Px) activity were measured on 10 calves with WMD and nine of their dams. The main clinical symptoms of the 10 calves with WMD were motor disturbances including recumbency and stiffness. Serum enzyme activities (GOT, GPT, CPK, LDH) in calves with WMD increased markedly, and this increase was also observed in some of their dams. Serum tocopherol levels of calves with WMD were low, 70% of which showing deficient levels of less than 70 micrograms/100 ml. Serum selenium levels of all the calves were lower than 35 ppb, indicating a deficiency, and were accompanied by low blood GSH-Px activity. alpha-Tocopherol and selenium concentrations in organs were very low. Dams of calves with WMD showed low serum tocopherol levels, 22% of which indicating deficient levels below 150 micrograms/100 ml. Serum selenium levels in dams showed a marked decrease to under 20 ppb, and also low blood GSH-Px activity. Feedstuffs supplied in the farms to affected calves indicated very low alpha-tocopherol contents (below 3 mg/100g DM) and low selenium concentrations below 50 ppb in DM. It was concluded that WMD in calves was attributable to nutritional muscular dystrophy caused by deficiencies in tocopherol and selenium in feedstuffs supplied to their dams.     

The levels of selenium and glutathione peroxidase activity in blood of sheep, cows and pigs.

The levels of selenium (Se) and glutathione peroxidase (GPX) in the blood of sheep, cows and pigs under farm conditions were examined. Sheep appear to form two distinct groups, namely high Se and GPX and low Se and GPX. The high group gave ranges of 133-249 ng/ml and 77-179 iu/g Hb for blood Se and GPX respectively, while the low group showed levels of 21-67 ng/ml and 2-20 iu/g Hb. Overall sheep blood showed a high correlation between Se and GPX (r = 0-92, P less than 0-001). Cow bloods formed one group, all having low Se and GPX levels except for a single outlier. Omitting this animal, the overall ranges were 9-72 ng/ml and 6-36 iu/g Hb for Se and GPX respectively. Blood Se and GPX activity were significantly correlated (r = 0-59, P less than 0-001). Pigs formed a single group also, with the difference that while their blood Se was high, the corresponding blood GPX activities were relatively low. Overall ranges were 93-193 ng/ml and 17-69 iu/g Hb for Se and GPX respectively. Correlation between blood Se level and GPX activity in this species was not significant (r = 0-27, P more than 0-1).     

Studies on serum tocopherol and selenium levels and blood glutathione peroxidase activities in lambs with white muscle disease

For the investigation of the cause of white muscle disease (WMD), tocopherol (Toc) and selenium (Se) levels and blood glutathione peroxidase (GSH-Px) activities were examined using lambs with WMD and their ewes. Serum Se levels of 4 lambs with WMD were low under 30 ppb, lambs showing very low levels below 15 ppb. The serum Se level was correlated with blood GSH-Px activity showing remarkably low activities in the lambs with WMD. Se contents in the organs of lambs with WMD were lower than those of control lambs, and particularly liver Se contents were deficient levels below 50 ppb. Serum Toc levels were normal, but alpha-Toc contents in organs showed very low levels, especially in the liver. The serum Toc and Se levels and blood GSH-Px activities of their ewes and other sheep kept in the same farm revealed similar results to those of lambs with WMD. Feedstuffs supplied on the farm showed the deficient level of the Se content below 50 ppb and a very low level of alpha-Toc. It was concluded that WMD of lambs in Hokkaido was nutritional muscular dystrophy resulted from deficiencies of Toc and Se to their ewes.     

Effects of monensin on the bioavailability and elimination of selenium from blood in lambs

A bioavailability study was conducted in lambs following intravenous and oral administration of sodium selenite (0.4 mg selenium/kg body weight) with and without concurrent oral monensin. Two- or three-compartment open models with first-order absorption after oral administration adequately described plasma selenium disposition irrespective of whether monensin was being administered. No significant differences were observed between groups of lambs receiving intravenous selenium with or without monensin with respect to distribution or elimination half-lives of selenium, areas under the concentration-time curve (AUC), volumes of distribution (Vd(ss)), or clearances (Cl). In lambs given selenium per os, no significant differences were observed with animals receiving monensin as well with respect to absorption and elimination half-lives, Vd(ss), or the time at which peak selenium concentrations occurred (tmax). However, peak selenium levels (Cmax) and AUC values were significantly higher in the group given monensin. The bioavailability of selenium with and without monensin was estimated to be 60% and 43%, respectively.     

Effect of dietary selenium and vitamin E on the primary and secondary immune response in lambs challenged with parainfluenza3 virus

This study was conducted to determine the effect of dietary selenium (Se) and vitamin E (Vit E) on various blood characteristics and the primary and secondary humoral immune response of lambs challenged with parainfluenza3 virus (PI3 V). Treatments included: 1) +Se/+Vit E, 2) -Se/+Vit E, 3) +Se/-Vit E and 4) -Se/-Vit E. The basal diet (-Se/-Vit E) was deficient in Se and Vit E. Sodium selenite (.2 mg Se/kg diet) and alpha-tocopherol acetate (20 mg Vit E/kg diet) were added to +Se and +Vit E diets, respectively, to provide adequate levels of each according to NRC recommendations. Following a 10-wk dietary adaptation and depletion period, lambs in all treatment groups were intratracheally inoculated with PI3 V on d 0 and 35 of the 70-d study. Prior to inoculation, whole blood and plasma glutathione peroxidase (GSH-Px) activities were higher (P less than .01) for +Se lambs. Whole blood and plasma GSH-Px increased (P less than .01) after primary viral inoculation in +Se lambs but not in -Se lambs. Serum immunoglobulin M (IgM) concentrations were enhanced (P less than .05) by Se supplementation on d 14, 35 and 49 of the study. Selenium and (or) Vit E did not affect serum immunoglobulin G (IgG) levels. Serum PI3 V antibody titers increased after inoculation on d 0 and 35 in all treatment groups. Titer levels appeared to increase more substantially for +Se lambs after primary inoculation, but increases were greater (P less than .01) for +Vit E lambs after secondary challenge.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood selenium in naturally fed horses and the effect of selenium administration

Blood Se of adult horses was 26.1, 25.8, and 27.0 ng/ml (mean values at 3 farms), where the Se of food was about 20 ng/g dry substance. Experimental adult horses which received about 41 ng Se/g food showed 45.3 ng/ml blood.At low Se intake suckling foals show higher blood Se than mares, but with high Se intake, the opposite will occur. This is reflected in milk Se, which raises but slowly with rise of mare’s blood Se.Se in blood plasma and in blood corpuscles is on the same level. The effect of various dose levels of Se on blood Se was studied: From 1.5 to 6 mg Se/week, blood Se rose rather linearity; 18 and 30 rag Se/week gave but slightly more effect than 6 mg.     

Selenium supplementation in lambs: effects on antibody responses to a salmonella vaccine

In trials conducted in 1984 and 1985, the effects of selenium injections on the antibody responses of lambs marginally deficient in selenium to Salmonella dublin were assessed. Control lambs (mean glutathione peroxidase [GSHPx] less than 20 iu/ml) responded well to the vaccine. No difference was observed in the antibody titres of animals treated twice with 5 mg selenium as sodium selenate. During the following season animals given 50 mg selenium as barium selenate showed slightly higher titres than controls. The results show that marginally selenium deficient lambs are able to elicit strong antibody titres to a bacterial antigen and that supplementation with selenium produces, at best, a marginal enhancement of the responses observed.     

AN EXAMINATION OF THE SELENIUM NUTRITION OF SHEEP IN VICTORIA

The selenium nutrition of sheep throughout Victoria was assessed by a survey of the blood glutathione peroxidase activity in 708 flocks. It was shown that the blood glutathione peroxidase activity in sheep had a seasonal variation with lowest levels in the spring. The enzyme activity was correlated with the blood selenium concentration. Areas where blood selenium was less than 0.03 μg/ml in spring were defined. Sheep with low selenium nutrition were grazing pastures in the high rainfall areas on acid soils, particularly those derived from granite.
Selenium concentrations in pasture samples examined were greater than 0.02 mg/kg, and it was found that superphosphate application had no significant effect on the selenium content of pasture. However, management practices such as high stocking rates and rates of application of superphosphate to pasture were associated with low blood glutathione peroxidase activities in sheep.
It was concluded that the selenium nutrition of most of the sheep flocks in Victoria is adequate, and that the deficient areas are localised. There seems little requirement for supplementation of adult sheep. As the delayed type of white muscle disease in spring lambs appears to be the main selenium-responsive disorder, direct supplementation of lambs in the low selenium areas would be the most effective method of ensuring adequate selenium nutrition.     

Selenium in New Zealand pastures

In grasses and clovers the highest concentrations of selenium were found in the leaves. The selenium content of different species in spring pastures on the same soil type did not vary widely although the slower growing and more deeply rooting species contained higher levels. The concentration of selenium in a pasture varied with time of the year, the lower levels being usually associated with conditions that stimulated rapid growth of the herbage, although factors other than growth rate were also involved. Lucerne appeared to be unusual in that in some areas it accumulated much higher levels of selenium than was found in other associated species. A very wide variation in levels of selenium in pastures growing on different soils has been observed 3-1500 ng/g). Selenium-responsive unthriftiness in grazing lambs occurred where the selenium content of spring pastures was <20 ng/g. Pastures containing >30 ng/g were apparently adequate while intermediate levels were probably marginally deficient.     

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 microg/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.     

The influence of dietary selenium levels on blood levels of selenium and glutathione peroxidase activity in the horse

Twenty mature geldings, averaging 535 kg, were used to determine the influence of dietary selenium (Se) on the blood levels of Se and Se-dependent glutathione peroxidase (SeGSH-Px) activity in the horse. Horses were randomly assigned within breed to four treatments consisting of five horses each and fed a basal diet containing .06 ppm of naturally occurring Se. Diets were supplemented with .05, .10 and .20 ppm Se, as sodium selenite. Blood was drawn for 2 wk before, and for 12 wk following, the inclusion of supplement Se in the diets. Whole blood and plasma Se concentrations and plasma SeGSH-Px activities were determined from all blood samples. Selenium concentrations in plasma and whole blood increased linearly from wk 1 to wk 5 and 6, respectively, in Se-supplemented horses. After these times, no significant changes in Se concentration were observed in Se-supplemented or in unsupplemented horses throughout the remainder of the 12-wk trial. Plasma Se reached plateaus of .10 to .11, .12 to .14, and .13 to .14 micrograms/ml in horses supplemented with .05, .10 and .20 ppm Se, respectively. Whole blood Se reached plateaus of .16 to .18, .19 to .21, and .17 to .18 micrograms/ml in horses supplemented with .05, .10 and .20 ppm Se, respectively. Plasma SeGSH-Px activity was not significantly affected by dietary treatment. Therefore, this enzyme was not a good indicator of dietary Se in these mature horses.