Selenium is an essential trace element important for many physiological processes, especially for the functions of immune and reproductive systems, metabolism of thyroid hormones, as well as antioxidant defense. Selenium deficiency is usually manifested by an increased incidence of retention of placenta, metritis, mastitis, aborts, lowering fertility and increased susceptibility to infections. In calves, lambs and kids, the selenium deficiency demonstrates by WMD (white muscle disease), in foals and donkey foals, it is associated with incidence of WMD and yellow fat disease, and in pigs it causes VESD (vitamin E/selenium deficiency) syndrome. The prevention of these health disorders can be achieved by an adequate selenium supplementation to the diet. The review summarizes the survey of knowledge on selenium, its biological significance in the organism, the impact of its deficiency in mammalian livestock (comparison of ruminants vs. non-ruminants, herbivore vs. omnivore) and possibilities of its peroral administration. The databases employed were as follows: Web of Science, PubMed, MEDLINE and Google Scholar.

https://www.mdpi.com/1422-0067/18/10/2209/pdf

A Summary of New Findings on the Biological Effects of Selenium in Selected Animal Species-A Critical Review.

This paper evaluates the impact of long-term supplementation of different forms of zinc (Zn) and selenium (Se) on the content of these substances in the blood and hair of goats. Two analogous supplementation experiments were performed. 37 goats divided into four groups were used in the first trial with the Zn supplemen- tation. Group A (n = 10) was a control group (with no Zn administered). A further three groups (B, C, D) were supplemented with Zn in various forms. Group B (n = 9) with zinc oxide, Group C (n = 9) with zinc lactate and Group D (n = 9) with zinc chelate. The second trial with Se supplementation was carried out on 20 goats divided into four groups. Group E (n = 5) was a control group. The other three groups were administered Se. Group F (n = 5) was supplied with a selenium lactate-protein complex, Group G (n = 5) with sodium selenite and Group H (n = 5) with selenium yeast. Three months later blood and hair samples were taken from all animals and Zn and Se concentrations were determined in whole blood, plasma, and hair. Glutathione peroxidase (GSH-Px) activity was determined in the Se supplementation trial group. At the end of the trial the Zn concentrations in plasma and whole blood were without major differences between the groups. The plasma concentration of Zn did not increase from the initial value at the start of the trial. In hair the average concentration of Zn was 95.2-100.0 mg/kg in all groups. No conclusive relation was confirmed between the values of Zn in hair and its concentration in blood. The Se concentration in whole blood (µg/l) at the end of trial in supplemented groups (F - 188.8 ± 24.6; G - 197.2 ± 10.9; H - 190.1 ± 26.3) was significantly higher (P < 0.01) than in the control group (E - 103.1 ± 23.5). Similarly, the activity of GSH-Px (µkat/l) was significantly higher in all supplemented groups (F - 872.3 ± 94.8; G - 659.5 ± 176.4; H - 839.8 ± 150.8) than in the control group (E - 379.1 ± 63.5). Se content in hair (µg/kg) was higher also in all trial groups (F - 242.3 ± 41.5; G - 200.5 ± 46.9; H - 270.0 ± 106.8) than in the control group (E - 174.7 ± 38.0). However, it was significantly (P < 0.05) higher only in Group F. A conclusive correlation was identified between the Se concentration in whole blood and its content in hair (r = 0.54; P < 0.05; n = 20). Based on the results it can be concluded that none of the supplemented forms of Zn increased its concentration in blood, plasma and hair. On the other hand, the administration of Se led to an increase in the Se concentration in blood, increased the activity of GSH-Px in whole blood and the Se content in hair. Based on the proven correlation and regression relation between the Se concentration in blood and its content in hair, hair can be considered as a suitable material for the diagnosis of long-term Se status in goats. Goats with sufficient Se status are those that have more than 160 µg/kg of Se in hair dry weight.

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Impact of long-term supplementation of zinc and selenium on their content in blood and hair in goats.

A 22-year-old, 395 kg Arabian mare used as a pleasure horse was presented to the Equine Department of the Vetsuisse Faculty, University of Zurich, with a 2-day history of dysphagia, salivation, and bilateral swelling of the masseter muscles. Previous treatment with flunixin meglumine had not resulted in improvement. None of the other horses on the premises showed similar clinical signs. On admission, the mare was slightly lethargic. Her rectal temperature (37.7°C) and respiratory rate (16 breaths/min) were within normal limits, but moderate tachycardia (60 beats/min) was present. On auscultation, neither cardiac murmurs nor arrhythmias were detected and lung sounds were normal. Both masseter muscles were severely swollen and painful, and the mare was hypersalivating. She had a good appetite, but masticatory efforts were ineffective. The motility and tone of the tongue appeared normal, but she was unable to move food to the back of the mouth to be swallowed. The mouth could be manually opened only the width of one finger. Her gait was normal and no other skeletal muscles were swollen, stiff, hardened, or painful. No other abnormalities were detected. Laboratory findings on the day of admission (day 1) are summarized in Table 1. Hematology results were within the normal reference ranges. Abnormal serum biochemistry results included marked increases in the activities of liver and muscle enzymes. Serum selenium concentration was below the lower limit of the reference range, whereas serum vitamin E concentration was normal. The mare’s urine was dark brown and urine dipstick analysis showed severe pigmenturia. Upper airway endoscopy (including the guttural pouches), palpation, and endoscopic examination of

Laboratory, Electrocardiographic, and Echocardiographic Detection of Myocardial Damage and Dysfunction in an Arabian Mare with Nutritional Masseter Myodegeneration

White muscle disease (WMD) is a nutritional myopathy caused by selenium (Se) deficiency. In most soils, Se is present in low concentrations, sometimes even below 0.2 mg/kg, a trend which is seen in many countries. Apart from total soil Se concentrations, soil conditions may be such that the bio-availability of Se is so low that it causes very low uptake in plants which can ultimately lead to deficiency problems in animals. This is the first case series to report clinical WMD in foals in areas deficient in Se, in the Netherlands. The aim of the current report is to provide an overview of the clinical history, symptoms and (clinical) pathology of 8 newborn foals living at 4 different premises and suffering from WMD together with the effectiveness of Se and vitamin E (Vit E) supplementation in the affected foals, their dams and herd members. Hands on practical information is provided to apply a correct and effective Se supplementation management in horses and which pitfalls need to be avoided for a successful approach. Case features and history were mapped out for all foals. Se and Vit E status were assessed for the foals, their dams and herd members, at admission and after 3 months of Vit E/Se supplementation. Common symptoms were muscle weakness, inability to rise, lethargy and inadequate suckle reflex together with increased serum muscle enzymes and low glutathione peroxidase (GSH-Px) and low to normal serum vit E levels. Necropsy revealed necrosis of skeletal muscles consistent with nutritional myopathy. Se status of the dams and herd members correlated well with the Se status of the foals. All surviving foals (n = 6) showed normal Vit E and GSH-Px levels after supplementation, likewise, all horses tested at premises 1, 3 and 4. However, dams and herd members in premises 2 showed no normalization. Horses of that premises were diagnosed with pyrrolizidine intoxication one year prior to the study. Certain regions in the Netherlands are sufficiently Se deficient to predispose newborn foals to develop WMD, especially when they are being fed a diet that mainly consists of locally harvested roughage.

https://link.springer.com/content/pdf/10.1186/s12917-017-1040-5.pdf

White muscle disease in foals: focus on selenium soil content. A case series

Effect of various doses and forms of selenium (organically bound vs inorganic) on selected parameters of ruminal fluid and blood in sheep was evaluated The trial was performed with 15 sheep divided into two groups Animals from group A ( n = 8) received a feeding mixture with selenomethionine, while sheep from group B ( n = 7) were fed a mixture with sodium selenite During the first 14 days, animals from both groups were fed a mixture with optimum dose of selenium (1 mg Se/kg dry matter) For another 28 days, all experimental animals received a Se-deficient mixture (01 mg Se/kg dry matter), whereas in the last 21 days of the experiment, animals were fed a high-Se diet (50 mg Se/kg dry matter) Throughout the trial, 4 samples of blood and ruminal fluid were taken from each animal The samples of ruminal fluid were analyzed to deter - mine the concentration of Se and identify other parameters of ruminal fermentations Selenium levels were also determined in ruminal biomass In blood, Se concentration, glutathione peroxidase (GSH-Px) activity, and other selected biochemical parameters were measured The results of the present study demonstrate that the actual intake of both organic and inorganic Se is reflected in Se concentration in ruminal fluid and ruminal biomass and, similarly, in Se content and GSH-Px activity in blood The form of supplemented selenium did not have a significant effect on ruminal fermentation parameters in dependence on different doses of Se contained in feeding rations (except for the negative effect of a sudden start of feeding high levels of organically bound Se on infusoria count, which was accompanied by the increase of GMT, LDH, and AST enzymes activity in ruminal fluid) The results also suggest possible negative interaction between the intake of organically bound selenium and the concentration of copper in blood of sheep

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Effect of supplementation of various selenium forms and doses on selected parameters of ruminal fluid and blood in sheep

Ludvikova E., L. Pavlata, M. Vyskoail, P. Jahn:Selenium Status of Horses in the Czech Republic. Acta Vet. Brno 2005, 74: 369-375. The aim of this study was to determine the relation between selenium concentration and activity of glutathione peroxidase (GSH-Px, EC 1.11.19) in whole blood of horses, reference ranges for the activity of GSH-Px and to evaluate the selenium status of horses in the Czech Republic. Blood samples were collected from 159 horses from 35 different farms and processed using the AAS and photometric methods to determine concentrations of selenium and the GSH-Px activity, respectively. Data on both parameters were processed using correlation and regression analysis in order to obtain reference values of GSH-Px for the indirect evaluation of the selenium status of horses. The results were also used to evaluate the occurrence of selenium deficiency in the horses examined. A highly significant linear relation was found between both variables. It can be expressed using the Spearman’s coefficient of rank correlation (r s = 0.873; p < 0.01) and the regression equation (y = 3.621x – 28.698; p < 0.01, r = 0.842). The value of 75 µg·l -1 of selenium in whole blood is considered as a threshold of selenium deficiency in horses. According to our results, the corresponding level of the activity of GSH-Px useful in the diagnostics is 200 µkat·l -1 . Using these criteria, there was a high prevalence of selenium deficiency in the collection of horses examined amounting to 47% and 48% when evaluating the selenium status by the selenium concentration and the activity of GSH-Px, respectively. It can be concluded that there is a high correlation of the activity of GSH-Px and selenium concentration in whole blood of horses and that reference values of the activity of GSH-Px useful in the diagnostics of selenium deficiency in horses in the Czech Republic were determined. The occurrence of selenium deficiency in horses is a topical problem in the Czech Republic.

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Selenium Status of Horses in the Czech Republic

Ludvikova E., P. Jahn, L. Pavlata, M. Vyskoail: Selenium and Vitamin E Status Correlated with Myopathies of Horses Reared in Farms in the Czech Republic. Acta Vet. Brno 2005, 74: 377-384. The objective of the study was to compare selenium and vitamin E status in equine farms with and without occurrence of myopathies in order to evaluate the role of lack of these substances in the aetiology of myopathies in horses in the Czech Republic. Concentrations of selenium (in 136 horses) and vitamin E (in 131 horses) and glutathione peroxidase (GSH-Px) activities (in 136 horses) were measured in horses from farms with the occurrence of myopathies (group M including 46 horses from 10 farms) and in horses from farms without occurrence of myopathies (group H including 90 horses from 22 farms). Significantly lower concentrations of selenium (43.09 ±36.84 µg·l -1 ; p < 0.001), vitamin E (9.55 ± 9.29 µmol·l -1 ; p < 0.01) and GSH-Px activities (153.38 ± 177.28 µkat·l-1; p < 0.001) were found in horses from the farms with the occurrence of myopathies when compared to those without the occurrence of myopathies (Se 117.35 ± 52.10 µg·l-1; vitamin E 10.75 ± 4.34 µmol·l-1; GSH-Px 397.41 ± 242.15 µkat·l-1). The diagnosis of nutritional myodegeneration (white muscle disease, WMD) was established in six horses with myopathy. The aetiology of myopathy in the other four affected horses was probably different. Evaluating all examined horses, insufficient whole blood selenium and serum vitamin E concentrations were found in 42% and 96% of horses, respectively. Poor saturation with selenium and vitamin Eare important factors in the aetiology of WMD in horses in the Czech Republic. Apart from WMD, horses in the Czech Republic may be affected by some other myopathies. Glutathione peroxidase, nutritional myodegeneration, white muscle disease, tocopherol, creatine kinase, aspartate aminotransferase

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L. Pavlata

Papers

Selenium Status of Horses in the Czech Republic

Selenium and Vitamin E Status Correlated with Myopathies of Horses Reared in Farms in the Czech Republic