Selenium elimination in pigs after an outbreak of selenium toxicosis.

In May 1996, 150 grower pigs in 5 California counties were exposed to selenium-contaminated feed distributed by a single feed company. Feed samples from 20 herds had a mean selenium concentration of 121.7 ppm dry weight (range, 22.1-531 ppm). In San Luis Obispo County, 52 pigs in 24 herds were exposed to the feed, and 8 pigs died with signs of paralysis. Bilateral symmetrical poliomyelomalacia involving the ventral horns of the cervical and lumbar intumescence was evident on histologic examination of spinal cord from affected pigs. Of 44 surviving exposed pigs, 33 (75%) exhibited signs of selenosis, including anorexia, alopecia, and hoof lesions. Thirty-nine of 44 pigs (88.6%) had elevated (>1 ppm) blood selenium concentrations. Surviving exposed pigs were changed to a standard commercial ration containing approximately 0.5 ppm (dry weight) selenium. Blood selenium concentrations were determined weekly for 46 days following removal of the contaminated feed and were compared with values of 20 control pigs fed a standard commercial ration. Mean (+/-SD) blood selenium concentrations of exposed pigs were 3.2 +/- 2.6 ppm at the initial sampling and 0.4 +/- 0.1 ppm after 46 days. Mean blood selenium concentrations of < or = 0.3 ppm for control pigs at all samplings were significantly lower (P < 0.001) than concentrations for exposed pigs. Muscle and liver samples of 22 of the 44 exposed pigs were collected at slaughter approximately 72 days after withdrawal of the selenium-contaminated feed. Muscle samples had a mean selenium concentration of 0.36 ppm (wet weight). Liver samples had a mean selenium concentration of 1.26 ppm (wet weight). One liver sample had a selenium value in the toxic range for pigs (3.3 ppm wet weight; reference range, 0.4-1.2 ppm). A 1-compartment pharmacokinetic model of selenium elimination in exposed pigs was generated, and the geometric mean blood selenium elimination half-life was estimated to be 12 days. The 60-day withdrawal time recommended by the Food Animal Residue Avoidance Database was considered sufficient to allow safe human consumption of tissues from exposed pigs.     

Toxicosis in pigs fed selenium-accumulating Astragalus plant species or sodium selenate

Three groups of 5 pigs each were fed a high selenium (Se) diet by mixing either Astragalus praelongus (31.6 ppm Se in feed), A bisulcatus (31.7 ppm Se in feed), or sodium selenate (26.6 ppm Se in feed) with commercial hog feed. Ten control pigs were fed only commercial hog chow containing trace selenium (0.44 ppm Se). Pigs were fed for 9 weeks and necropsied when they had ataxia or paralysis. Blood was collected for hematologic and serum biochemical determinations, and samples of various tissues were collected and fixed in neutral-buffered 10% formalin for histologic evaluation or frozen for determination of selenium concentration. All forms of selenium induced clinical signs of weight and hair loss, with cracked hooves and inflamed coronary bands developing in all Na2SeO4-fed pigs and 1 A praelongus-fed pig, but not in A bisulcatus-fed pigs. Serum calcium, phosphorus, and albumin concentrations were unchanged or significantly decreased from prefeeding values in groups fed selenium. Serum aspartate transaminase (AST) activities in Astragalus species-fed groups, and amylase activities and PCV in all groups of pigs fed selenium, were increased. Serum alkaline phosphatase and creatine kinase activities were significantly increased in the A praelongus-fed pigs and significantly decreased in Na2SeO4-fed pigs. Terminal tissue and body fluid selenium concentrations were determined in all groups of pigs fed selenium and compared with values in control pigs. Urine and bile concentrations were increased by the greatest factor (40 to 100x), with tissue concentrations of selenium increased by a lesser factor (6 to 17x).(ABSTRACT TRUNCATED AT 250 WORDS)     

Retention of selenium in tissues of calves, lambs, and pigs after parenteral injection of a selenium-vitamin E preparation.

Four each healthy weaned calves, lambs, and pigs raised in Indiana without selenium supplementation were killed, and their tissues were fluorometrically analyzed to establish base line selenium concentrations. The following mean selenium content (in ppm, wet weight) was found in calves, lambs, and pigs, respectively: liver, 0.12, 0.16, and 0.19; renal cortex, 0.63, 0.89, and 0.70; muscle, 0.05, 0.05, and 0.06. Eight each additional healthy weaned calves, lambs, and pigs were injected with a commercial selenium-vitamin E preparation at dose levels of 0.0825, 0.055, or 0.06 mg of Se (as selenite) per kilogram of body weight, respectively. Selenium content of tissues was measured in animals killed at 1, 7, 14, and 23 days after injection. In calves, concentrations in liver and kidney rapidly increased to moderate values and then slowly decreased, with mean concentrations after 23 days still somewhat greater than base line values. Concentrations for injection site tissue also rapidly increased to moderate values, but had decreased to base line values by 23 days after injection. In lambs, selenium content of liver was moderately increased after injection, but had decreased to base line values after 14 days; kidney and injection site did not have increased selenium content after injection. In pigs, liver and kidney had moderate initial increases in concentration of selenium, but these were at base line values after 14 days, and increase did not occur at injection sites.     

The effects of salbutamol on blood pressure and heart rate in Large White and Pietrain-cross breeds of pig

The effects of the β2-agonist salbutamol, on pig heart rate and blood pressure were evaluated at the expected commercially used concentration of 3 ppm in final feed, and at three times this level. Salbutamol was administered to pigs previously fed on control diet (‘naive’), and in a second study to pigs fed 3 ppm salbutamol for 19 days (‘acclimatized’). Heart rate and blood pressure were measured in conscious 30 kg pigs before (pre-ingestive), during (ingestive) and after ingestion (absorptive) of feed containing 3 or 9 ppm salbutamol. To assess any interaction with ‘stress genotype’ pigs, measurements were performed in Large White and Pietrain-cross breeds. The mean preingestive heart rates for the Large White and Pietrain-cross pigs were 127 and 109 beats/min, respectively. The corresponding figures for mean arterial blood pressure were 121 and 122 mmHg. The act of ingesting control feed caused heart rate to rise by 36–39% and blood pressure to increase by 17–27%. During the absorptive phase for ‘naive’ pigs fed 3 ppm salbutamol in the diet, blood pressure fell 5–11% and heart rate increased 20–24%, reflecting a classical baroreceptor mediated response. At 9 ppm the fall in blood pressure of 5–11% was similar to that at 3 ppm, while the rise in heart rate was larger at 31–38%. The magnitude of the changes at both 3 and 9 ppm was less than that evoked by the act of ingestion, with the exception of the heart rate response in Large Whites at 9 ppm, which was similar. The responses of the two breeds were comparable, indicating that salbutamol is unlikely to exacerbate the cardiovascular responses seen in potentially stress-susceptible pigs. The acute changes elicited by 3 ppm salbutamol during the absorptive phase in ‘naive’ pigs were abolished or substantially less in acclimatized pigs, implying a tachyphylaxis to the agonist's actions. This was confirmed by 9 ppm of salbutamol increasing heart rate of ‘acclimatized’ Large Whites to the same degree as 3 ppm in ‘naive’ counterparts. The desensitization in Pietrain-cross pigs was even more marked with no increase in heart rate produced by 9 ppm salbutamol following acclimatization. These data, combined with the rapid tachyphylaxis of response, indicate that salbutamol at the intended commercial inclusion of 3 ppm will not compromise the cardiovascular stability of the growing pig at rest.     

Retention of Selenium in Tissues of Swine After A Single Intramuscular Administration of Sodium Selenite

The retention of selenium in pigs after a single intramuscular administration of a preparation containing sodium selenite and alphatocopherol was studied.At the site of injection the concentration fell from 0.8 ppm to normal 0.4 ppm in about a week.The concentration in the liver was 4.47 ppm after 4 hours, 2.18–2.38 ppm after 3 days, and on normal level (about 1.5 ppm) after 7 days. No increase was observed in the kidney or in the M. gracilis. It is concluded that the liver probably plays an important excretory role.     

HEPATOSIS DIETETICA, NUTRITIONAL MYOPATHY, MULBERRY HEART DISEASE AND ASSOCIATED HEPATIC SELENIUM LEVELS IN PIGS

Outbreaks of Hepatosis Dietetica (HD), Nutritional Myopathy (NM) and Mulberry Heart Disease (MHD) in Western Australia are described. Hepatic selenium concentrations were low in pigs with HD and NM, but not with MHD. The mean hepatic selenium concentration in pigs unaffected with these conditions was 1.07 +/- 0.12 ppm dry wt. Cereal grain in an area of Western Australia where HD and NM frequently occur was found to be low in selenium and the addition of 0.1 ppm selenium to pig rations appeared to be an effective prophylactic measure. The extensive use of lupin seed as a protein source replacing much of the meat meal in pig rations may have contributed to an increase in the incidence of HD and NM.     

Swine dysentery: the influence of dietary selenium on clinical and pathological effects of Treponema hyodysenteriae infection

Twenty-four conventionally reared pigs divided into 4 groups were fed a basic ration deficient in selenium. The following daily supplement of selenium was given per pig; Group 1: none, group 2: 0.2 mg, group 3: 0.4 mg and group 4: 0.8 mg. After 51 days all pigs were inoculated orally with a pure culture of Treponema hyodysenteriae, and subsequently observed for 26 days. Clinical signs of swine dysentery were seen in all 4 groups. Criteria such as morbidity rate, incubation time and weight gain showed that the non-supplemented pigs suffered more severely from swine dysentery than the supplemented ones. Best protection was found among the pigs given a daily supplement of 0.4 mg selenium, whereas a supplement of 0.8 mg had a negative influence on the resistance to swine dysentery. The results indicate that selenium plays a more complex role in mucosal defence mechanisms than hitherto anticipated.     

Fluorometric Selenium Determinations in the Liver of Normal Pigs and in Pigs Affected with Nutritional Muscular Dystrophy and Liver Dystrophy

The selenium concentration of livers and kidneys in normal pigs and in pigs affected with nutritional muscular dystrophy (NMD) and liver dystrophy (LD) was determined. The kidney values showed great variation in normal pigs. The young pigs generally had the lowest levels. The liver values were less scattered.In NMD and LD the liver contained about 0.2 ppm of selenium on the average, whereas normal livers contained about 1.2 ppm. Kidneys showed corresponding differences. This is in good agreement with the favourable results obtained with selenium therapy.     

Selenium toxicity and porcine focal symmetrical poliomyelomalacia: description of a field outbreak and experimental reproduction.

An acute afebrile paretic condition was diagnosed in 18 of 225 feeder pigs between eight to ten weeks of age. Nine pigs died acutely, seven pigs were euthanatized and two appeared to recover. Macroscopic lesions in the ventral horns of the cervical and lumbar/sacral spinal cord enlargements consisted of focal, bilateral, depressed areas. Histopathologically, the lesion consisted of endothelial proliferation, glial cell reaction and microcavitation. Similar lesions were observed in some brain stem motor nuclei. High selenium levels were detected in the pig feed and in pig tissues and blood. Two of five experimental pigs fed a commercial grower ration and supplemented with 52 ppm selenium as sodium selenite developed paresis and paralysis after a 29 day feeding trial. Histopathological lesions of focal symmetrical poliomyelomalacia confined to the cervical and lumbar/sacral spinal cord enlargements, and identical to those in the field cases, were produced. Select brain stem motor nuclei were also affected.     

Pathologic features of polybrominated biphenyl toxicosis in the rat and guinea pig.

Young male rats were fed a diet containing 0, 1, 10, 100, or 500 ppm of a commercial mixture of polybrominated biphenyls (PBB) that had been accidentally incorporated into a mineral mixture and fed to Michigan livestock and poultry. After 30 days, 9 of the 12 rats in each group were killed and tissues were examined. Liver weight to body weight ratios were significantly increased at all feeding levels; at 500 ppm, liver weight had more than doubled. Kidney weight was not affected. Microscopic lesions were mostly confined to the liver and consisted of extensive swelling and vacuolation of hepatocytes in rats fed diets containing 100 and 500 ppm of PBB. Slight swelling and vacuolation were seen in rats fed the diet containing 10 ppm, and lesions were not found at 0 or 1 ppm. There was a significant increase in hepatic mitochondrial size at 1 ppm, and smooth endoplasmic reticulum was markedly increased at 100 and 500 ppm. Myelin bodies were present at 100 and 500 ppm, and vacuoles were numerous. Rats killed at 60 days had similar lesions. The activity of hepatic microsomal enzymes increased at all levels of feeding of PBB. Rat pups nursing dams fed a diet containing 10 ppm of PBB had microscopic and ultrastructural hepatic lesions. When guinea pigs were fed PBB at the same amounts as were rats, the results were strikingly different. Guinea pigs fed a diet containing 500 ppm of PBB died within 15 days; at 100 ppm, only 2 of 6 survived for 30 days. Effects on liver weight were inconsistent, but 2 of 6 fed a diet containing 10 ppm had enlarged livers.     

Vitamin E and selenium concentrations in livers of pigs diagnosed with mulberry heart disease.

During a 2-year period from January 1, 1999, to December 31, 2000, 77 diagnoses of mulberry heart disease (MHD) were documented at the Iowa State University Veterinary Diagnostic Laboratory. Mean (+/- SD) liver vitamin E concentrations were lower (P < 0.05) in pigs with MHD (3.12 +/- 1.12 ppm, wet weight) than in pigs that died of causes other than MHD (4.80 +/- 3.2 ppm, wet weight). The majority of the pigs affected with MHD ranged in age from 3 to 7 weeks. Statistical influence of age was found on the concentration of vitamin E (P < 0.01) but not on concentration of selenium in liver in pigs with MHD. Concentrations of vitamin E below 2 ppm were considered deficient. Hepatic vitamin E concentrations below 2 ppm were measured in 25% of the pigs with gross and microscopic lesions of MHD. In contrast, liver selenium concentrations were adequate in all pigs.     

The effect of monensin against swine dysentery

The use of monensin sodium against naturally transmitted swine dysentery was evaluated in 4-week-old piglets, with an average weight of 8 kg, over a period of 112 days. Three treatments were compared using between two and four pens per treatment and 12 pigs per pen. Monensin was administered via the feed, either immediately post weaning to four pens of pigs (T1), or after 12 days (T2, two pens). The T1 group received monensin at the rate of 100 ppm (days 0-56), 50 ppm (days 57-84) and 25 ppm until the end of the trial. In the other group monensin was given at 100 ppm (days 12-84) and at 50 ppm (days 85-112). Unmedicated feed was given to two pens (T3). The continuous administration of monensin from weaning was effective in the control or prevention of swine dysentery. A significant (P less than 0.05) improvement, in comparison with the other two groups, was observed in terms of mortality, diarrhoea score, average daily gain (ADG) and feed conversion ratio (FCR). There was a reduction in mortality, diarrhoea score/days and an improvement in growth performance parameters in pigs treated with monensin after the disease had been established, with ADG and FCR values significantly (P less than 0.05) different compared with the untreated controls.     

A field evaluation of mortality rate and growth performance in pigs vaccinated against porcine circovirus type 2

OBJECTIVE: To evaluate, under field conditions, the effects of a commercial porcine circovirus type 2 (PCV2) vaccine on mortality rate and growth performance in a herd infected with PCV2 that had a history of porcine circovirus disease. DESIGN: Randomized controlled clinical trial. ANIMALS: 485 commercial, cross-bred, growing pigs. PROCEDURES: Prior to weaning, pigs were randomly assigned within litter to a vaccination or unvaccinated control group. Pigs in the vaccination group were given a commercial PCV2 vaccine at weaning and 3 weeks later. Mortality rate was recorded, and pigs were weighed prior to vaccination, when moved from the nursery, and prior to marketing. Infection status was assessed by serologic testing and detection of viral DNA in serum. RESULTS: Compared with control pigs, pigs vaccinated against PCV2 had a significantly lower mortality rate during the finishing phase, significantly higher average daily gain during the finishing phase, and significantly lower likelihood of being lightweight at the time of marketing. For vaccinated pigs, overall mortality rate was reduced by 50% and average daily gain during the finishing period was increased by 9.3%. At the time of marketing, vaccinated pigs weighed an average of 8.8 kg (19.4 lb) more than control pigs, without any difference in days to marketing. Serum PCV2 antibody titers increased in control pigs, and PCV2 DNA was detected, indicating active PCV2 infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that vaccination against PCV2 was effective at reducing mortality rate and improving growth performance among pigs in a herd infected with PCV2.     

生长猪对微量元素硒需要量的初步研究

<正> 硒是动物营养所必需的微量元素,缺硒不但引起人畜发生一系列营养疾病,如人的克山病,幼畜的白肌病以及人畜心脏,肝脏等病变,而且影响家畜的发育,繁殖等,对畜禽生产力危害甚为严重,所以近些年来硒的营养作用在国内外引起了普遍注意。     

Vitamin E, Selenium and Methionine Supplementation of Dystrophogenic Diets for Pigs

Forty-eight weanling S.P.F. Yorshire pigs were used to study the influence of supplemental vitamin E (25 IU per kg of diet) selenium (0.5 ppm in diet) and methionine (0.1% in diet) on the incidence of hepatosis dietetica and mulberry heart disease when fed a torula yeast-corn diet. Vitamin E and/or selenium increased pig survival. Supplemental selenium resulted in increased liver selenium concentrations. No hepatosis dietetica was observed in any of the pigs. The addition of vitamin E and/or selenium at the levels used did not reduce the frequency of myocardial lesions; however, they prevented skeletal muscular dystrophy and exudative diathesis. The myocardial lesions were less severe in supplemented pigs compared with unsupplemented controls.     

Effects of dietary selenium and moisture on the physical activity and thyroid axis of cats

Consumption of canned cat food is considered a risk factor for the development of feline hyperthyroidism. Because selenium and water are substantially higher in canned diets compared to dry diets, objectives of this study were to determine whether increased dietary selenium or water alters the function of the hypothalamic–pituitary–thyroid axis and leads to an increase in activity level. Employing a 28‐day latin square design with a 14‐day washout, six lean, neutered male domestic shorthair cats were fed (i) commercially available adult dry feline diet containing 0.8 ppm selenium (control), (ii) control diet with added sodium selenite to achieve a dietary selenium concentration of 1.125 ppm (selenium treatment) and (iii) the control diet with additional water to achieve a moisture content of 75% wt/wt (water treatment). Water consumption was determined using deuterium oxide washout. Actical activity monitors were placed on each cat's collar to allow quantification of the activity of each cat. Circulating serum T3 and T4 was measured on days 0, 14, and 28. On day 28, a thyrotropin‐releasing hormone (TRH) stimulation test was conducted to determine treatment effects on serum concentrations of thyroid hormones. There was a significant increase in daily water consumption with dietary water treatment (192 ml ± 7.85 SEM) compared to the control (120 ml ± 20.4) and selenium (116 ml ± 14.6) treatments. Both water and selenium treatments were associated with greater (p < .05) activity over that of the control treatment by 20.5% and 11% respectively. Serum TT3 AUC concentrations (0–4 hr) of TRH stimulation tests were greater (p < .05) by 16% with water compared to control treatments. The results of this study indicate that dietary water content may alter the function of the thyroid axis and that this effect is associated with an increase in physical activity.     

Growth and intestinal morphology of pigs from sows fed two zinc sources during gestation and lactation

An experiment was conducted to compare the effects of organic (Zn AA complex, ZnAA) and inorganic Zn (ZnSO4) sources on sows and their progeny during gestation and lactation and on the pigs during the nursery period. The dietary treatments were 1) a corn-soybean meal diet with 100 ppm Zn from ZnSO4 (control); 2) diet 1 + 100 ppm additional Zn from ZnSO4; and 3) diet 1 + 100 ppm additional Zn from ZnAA. Dietary additions were on an as-fed basis. Thirty-one primaparous and multiparous sows were allotted to the treatment diet beginning on d 15 of gestation and continuing through lactation. At weaning (d 17 of age), 202 pigs (63, 55, and 84 pigs for treatments 1 to 3, respectively) were allotted to the same dietary treatment as their dam. The pigs were fed a 3-phase diet regimen during the nursery period: d 0 to 7 (phase I); d 7 to 21 (phase II); and d 21 to 28 (phase III). At weaning and at the end of phase III, 1 gilt per replicate was killed, and the left front foot, liver, pancreas, and entire small intestine were removed. Diet had no effect (P > 0.10) on any response during gestation. During lactation, there was an increase (P < 0.10) in litter birth weight in sows fed ZnAA compared with those fed the control or ZnSO4 diets. The sows fed ZnAA nursed more pigs (P < 0.10) than sows fed the ZnSO4 diet, and they weaned more pigs (P < 0.05) than sows fed the control diet. Jejunal villus height of the weaned pigs from sows fed ZnSO4 was increased (P < 0.05) compared with those from the sows fed the control diet. During the nursery period, growth performance was not affected (P > 0.10) by diet. Pigs fed ZnSO4 had greater duodenal villus width (P < 0.05) than those fed ZnAA, and pigs fed ZnSO4 or the control diet had greater ileal villus width (P < 0.05) than those fed ZnAA. Pigs fed ZnSO4 or ZnAA had more (P < 0.05) bone Zn than those fed the control diet. Liver Zn concentration was greatest in pigs fed ZnSO4, followed by those fed ZnAA, and then by those fed the control diet (P < 0.05). Pancreas Zn was increased (P < 0.05) in pigs fed ZnSO4 compared with those fed the control diet. These results suggest that 100 ppm Zn in trace mineral premixes provides adequate Zn for optimal growth performance of nursery pigs, but that 100 ppm additional Zn from ZnAA in sow diets may increase pigs born and weaned per litter.     

Porcine focal symmetrical poliomyelomalacia: experimental reproduction with oral doses of encapsulated sodium selenite.

Sodium selenite (encapsulated as doses of 1.4 mg, 2.6 mg and 4.2 mg per kilogram of body weight) was given orally on a daily basis to male weaner pigs, and features of these animals were compared to a control group. Porcine focal symmetrical poliomyelomalacia was produced in all experimental groups between 3 and 20 days after initiation of the treatment. Analysis of blood and several tissues revealed an elevated selenium content for all pigs. Histological lesions in the brain and the cervical lumbar/sacral spinal cord enlargements included endothelial proliferation, neuronal degeneration, microcavitation and glial cell reaction.     

Effects of replacing pharmacological levels of dietary zinc oxide with lower dietary levels of various organic zinc sources for weanling pigs

Two 28-d randomized complete block design experiments were conducted to evaluate the effects of concentrations and sources of Zn on growth performance of nursery pigs. Seven stations participated in Exp. 1, which evaluated the efficacy of replacing 2,500 ppm of Zn from ZnO with 125, 250, or 500 ppm of Zn from Zn methionine. A control diet with 125 ppm of supplemental Zn was included at all stations. A total of 615 pigs were used in 26 replicates. Average weaning age was 20.6 d and the average initial BW was 6.3 kg. There were no differences in any growth response among the three supplemental Zn methionine levels fed in Exp. 1. Zinc supplementation from Zn methionine improved ADG compared with the control during all phases (P < 0.05), due primarily to an increase in ADFI. Pigs fed 2,500 ppm of Zn from ZnO gained faster (P < 0.01) than those fed the control diet during all phases, and faster (P < 0.05) than those fed supplemental Zn from Zn methionine for the 28-d experiment. Differences in gain were again due mainly to differences in feed intake. A second experiment compared five sources of supplemental organic Zn (500 ppm of Zn) with 500 and 2,000 ppm supplemental Zn from ZnO and a control (140 ppm total Zn). Six stations used a total of 624 pigs, with an average weaning age of 20.4 d and averaging 6.2 kg BW in 15 replicates. Pigs fed 2,000 ppm of Zn from ZnO gained faster (P < 0.05) than pigs fed the control or any of the 500 ppm of Zn treatments (ZnO or organic Zn). Pigs fed the 2,000 ppm of Zn from ZnO also consumed more feed than those receiving 500 ppm of Zn from ZnO or from any of the organic Zn sources (P < 0.05). Organic sources of Zn did not improve gain, feed intake, or feed efficiency beyond that achieved with the control diet. Supplemental Zn at a concentration of 500 ppm, whether in the form of the oxide or in an organic form, was not as efficacious for improved ADG as 2,000 to 2,500 ppm of Zn from ZnO.     

Selenium dynamics in the blood of lambs from birth to weaning using traditional rearing technics]

The dynamics of selenium in the blood serum of 20 lambs of the Merino breed, traditionally reared, was followed from birth to weaning at the age of 110 days. Results of the observations revealed that the highest concentration of serum selenium was determined in lambs just after delivery (0.25 ppm) and the level was maintained throughout the period of colostral nutrition. In the period between the 15th and 60th day low selenium values (0.06-0.13 ppm) were recorded, which implies a critical period in relation to the origin of muscular dystrophy. At the end of the observations there appeared a significant selenium content increase in the blood serum of lambs.