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Topic:Selenium

Selenium is an essential trace mineral that is important for various physiological processes in horses. It is a component of several enzymes and proteins, including glutathione peroxidase, which plays a role in protecting cells from oxidative damage. Selenium is also involved in thyroid hormone metabolism and immune function. Horses require selenium in their diet, but the required amounts can vary based on factors such as age, workload, and geographic location, as soil selenium content influences forage selenium levels. Both selenium deficiency and toxicity can lead to health issues in horses, with deficiency potentially resulting in muscle disorders and toxicity causing symptoms such as colic and neurological signs. This page compiles peer-reviewed research studies and scholarly articles that explore the metabolism, dietary requirements, and health implications of selenium in equine nutrition and management.
Evaluation of dietary trace mineral supplementation in young horses challenged with intra-articular lipopolysaccharide.
Translational animal science    January 17, 2020   Volume 4, Issue 2 txaa006 doi: 10.1093/tas/txaa006
Millican AA, Leatherwood JL, Coverdale JA, Arnold CE, Bradbery AN, Larson CK, Lamprecht ED, White SH, Paulk CB, Welsh TH, Wickersham TA.Sixteen weanling Quarter Horses (255 ± 22 kg) were utilized in a 56-d trial to evaluate the effects of trace mineral (TM) source on intra-articular inflammation following a single acute inflammatory insult. Horses were stratified by age, sex, and BW and then randomly assigned to dietary treatment: concentrate formulated with Zn, Mn, Cu, and Co as inorganic sources (CON; n = 8) or complexed TMs (CTM; n = 8). Added TM were formulated at iso-levels across treatments and intakes met or exceeded NRC requirements. Horses were offered 1.75% BW (as-fed) of treatment concentrate and 0.75% BW (as-fed) ...
Interrelationships Between Age and Trace Element Concentration in Horse Mane Hair and Whole Blood.
Journal of equine veterinary science    January 11, 2020   Volume 87 102922 doi: 10.1016/j.jevs.2020.102922
Brummer-Holder M, Cassill BD, Hayes SH.The use of hair as a sample matrix to determine the mineral status of an animal has received a lot of interest. The objective of this study was to determine if the trace element content in horse mane hair changed with age when evaluated in a group of horses representing a large age range. As a second objective, whole blood trace element content was evaluated, and its relationship to mane hair trace element content, as well as age, were tested. Therefore, mane hair and whole blood samples were obtained from 59 horses, ranging from 2 months to 26 years in age, housed on the same farm. Mane hai...
Uterine Inertia due to Severe Selenium Deficiency in a Parturient Mare.
Journal of equine veterinary science    November 12, 2019   Volume 85 102845 doi: 10.1016/j.jevs.2019.102845
Busse NI, Uberti B.A 12-year-old, multiparous, parturient show jumper embryo-recipient mare presented at a veterinary hospital, seven days past her due date and with a dilated cervix, for evaluation of mild colic. Gastrointestinal or metabolic abnormalities and fetal maldispositions were excluded as causes of dystocia, and a diagnosis of uterine inertia was made. There was no uterine response to oxytocin treatment. A live filly was delivered via C-section, and severe selenium deficiency was eventually confirmed in the mare, her offspring, and in the herd of origin. The filly was born with severe white muscle dis...
Fatal Peritoneal Migration of Strongylus edentatus in a Foal.
Journal of comparative pathology    October 18, 2019   Volume 172 88-92 doi: 10.1016/j.jcpa.2019.09.004
Gonzales-Viera O, Fritz H, Mete A.A 7-month-old female mixed breed foal with a 2-day history of recumbency and inability to open its mouth convulsed acutely and died and was submitted for necropsy examination. The foal was thin and large patches of haemorrhage were present throughout the peritoneal wall, the diaphragmatic surfaces and the retroperitoneum. Numerous nematode larvae were visible on the serosal surfaces and penetrated and embedded into the subserosa associated with the haemorrhages. The dorsal portion of the abdominal diaphragm had a partial tear and large numbers of nematodes were within the muscle fibres. Histol...
The total content of toxic elements in horsehair given the level of essential elements.
Environmental science and pollution research international    June 24, 2019   Volume 26, Issue 24 24620-24629 doi: 10.1007/s11356-019-05630-z
Kalashnikov V, Zaitsev A, Atroschenko M, Miroshnikov S, Frolov A, Zavyalov O.Elemental status of 214 mares aged 3-7 years from 11 breeds was studied: Arabian purebred (n = 20), Bashkir (n = 20), Kabarda (n = 20), Vyatka (n = 20), Tuva (n = 19), Yakutsk (n = 30), Mezenskaya (n = 20), Thoroughbred (n = 20), Akhal-Teke (n = 20), Russian trotter (n = 15), Soviet Heavy Draft (n = 10) bred in 13 regions of Russia. The research objective is to study the content of chemical elements in hair from the horse's mane, depending on the sum of toxic elements in animal hair expressed in moles. The elemental composition of the hair was defined by atomic emission and mass spectrometry (...
Selenium and Vitamin E Concentrations in a Healthy Donkey Population in Central Italy.
Journal of equine veterinary science    April 25, 2019   Volume 78 112-116 doi: 10.1016/j.jevs.2019.04.003
Bazzano M, McLean A, Tesei B, Gallina E, Laus F.Selenium and vitamin E protect the body against oxidative stress. Clinical manifestations of their deficiency in equids include neurologic and muscular symptoms. Despite the importance of donkeys as working and production animals, there is a dearth of scientific data on selenium and vitamin E normal values. Therefore, the aim of this study was to investigate the plasma concentrations of selenium and vitamin E in healthy donkeys belonging to different ages, sexes, and productive phases. Animals were divided into five groups including foals (group A: n = 7, n = 4 males and n = 3 females), wea...
[Selenium Deficiency as a Potential Cause of Cribbing (Koppen)].
Tierarztliche Praxis. Ausgabe G, Grosstiere/Nutztiere    March 23, 2018   Volume 46, Issue 1 67 doi: 10.1055/s-0038-1638224
No abstract available
Submaximal exercise training, more than dietary selenium supplementation, improves antioxidant status and ameliorates exercise-induced oxidative damage to skeletal muscle in young equine athletes.
Journal of animal science    February 13, 2018   Volume 95, Issue 2 657-670 doi: 10.2527/jas.2016.1130
White SH, Warren LK.Exercise is associated with increased production of reactive oxygen species (ROS) as metabolism is upregulated to fuel muscle activity. If antioxidant systems become overwhelmed, ROS can negatively affect health and performance. Adaptation to exercise through regular training has been shown to improve defense against oxidative insult. Given selenium's role as an antioxidant, we hypothesized that increased Se intake would further enhance skeletal muscle adaptations to training. Quarter Horse yearlings (18 ± 0.2 mo; 402 ± 10 kg) were randomly assigned to receive either 0.1 or 0.3 mg Se/kg DM a...
Biochemical analysis of some serum trace elements in donkeys and horses in Eastern region of Kingdom of Saudi Arabia.
Veterinary world    October 25, 2017   Volume 10, Issue 10 1269-1274 doi: 10.14202/vetworld.2017.1269-1274
Shawaf T, Almathen F, Meligy A, El-Deeb W, Al-Bulushi S.Little is known about the serum levels of trace elements in donkeys and horses in Saudi Arabia. This study aimed to investigate the levels of some trace elements in these two species in the eastern region of Saudi Arabia and to compare the obtained results with the reference values. Methods: Seventeen Arabian horses and twenty eight Hassawi donkeys were randomly selected for this study. All of the studied healthy animals were kept under a uniform feeding protocol without any minerals supplementations. Atomic absorption spectrometer is used to estimate the serum concentrations of selenium (Se),...
A Summary of New Findings on the Biological Effects of Selenium in Selected Animal Species-A Critical Review.
International journal of molecular sciences    October 21, 2017   Volume 18, Issue 10 doi: 10.3390/ijms18102209
Hosnedlova B, Kepinska M, Skalickova S, Fernandez C, Ruttkay-Nedecky B, Malevu TD, Sochor J, Baron M, Melcova M, Zidkova J, Kizek R.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 cau...
Influences of different dietary contents of macrominerals on the availability of trace elements in horses.
Journal of animal physiology and animal nutrition    October 13, 2017   Volume 102, Issue 2 e633-e640 doi: 10.1111/jpn.12805
Neustädter LT, Kamphues J, Ratert C.In this study, influences of a reduced macromineral intake on the trace element metabolism in horses at maintenance were investigated. Background of this study is the revised recommendation on the macromineral supply for horses (GfE ). Balance studies on three adult pony geldings with body weights of 405 / 348 / 384 kg were performed to obtain data on apparent digestibility (aD), retention and serum concentrations of different trace elements (Cu, Zn, Se) at different dietary macromineral levels. A mineral supplement or a complementary feed-with a reduced macromineral content-was added to a ha...
Rapid Communication: Dietary selenium improves skeletal muscle mitochondrial biogenesis in young equine athletes.
Journal of animal science    October 11, 2017   Volume 95, Issue 9 4078-4084 doi: 10.2527/jas2017.1919
White SH, Wohlgemuth S, Li C, Warren LK.Exercise is known to promote mitochondrial biogenesis in skeletal muscle as well as enhance mitochondrial function and efficiency in human and rodent models. These adaptations help to decrease exercise-associated production of reactive oxygen species, which can negatively affect health and performance if antioxidant mechanisms are overwhelmed. Little is known about the adaptations of mitochondria in response to exercise training in the growing horse or if supplementation with a dietary antioxidant can improve mitochondrial function. To evaluate the separate and combined effects of selenium (Se...
Hoof Quality of Anglo-Arabian and Haflinger Horses.
Journal of veterinary research    September 19, 2017   Volume 61, Issue 3 367-373 doi: 10.1515/jvetres-2017-0049
Tocci R, Sargentini C, Martini A, Andrenelli L, Pezzati A, Benvenuti D, Giorgetti A.Foot quality is essential to the horse's movement. The barefoot approach favours the animal's welfare. Environment and selection determine hoof characteristics. Methods: Hoof characteristics of eight Anglo-Arabian (AA) and nine Haflinger (HA) horses were studied. After a preliminary visual analysis of feet, nail samples were collected after trimming for physico-chemical analysis. The parameters were submitted to analysis of variance. A principal component analysis and a Pearson correlation were used to compare mineral contents. Results: The hooves of both breeds were healthy and solid. The hoo...
White muscle disease in foals: focus on selenium soil content. A case series.
BMC veterinary research    May 3, 2017   Volume 13, Issue 1 121 doi: 10.1186/s12917-017-1040-5
Delesalle C, de Bruijn M, Wilmink S, Vandendriessche H, Mol G, Boshuizen B, Plancke L, Grinwis G.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 c...
Clinical and Pathologic Features of a Suspected Selenium Deficiency in Captive Plains Zebras.
Biological trace element research    August 23, 2016   Volume 176, Issue 1 114-119 doi: 10.1007/s12011-016-0820-2
Chen F, Gao J, Wu D, Xu L, Han W, Zhang D, Bi X, He M, Pan Y.Previous studies have shown that selenium (Se) deficiency is associated with nutritional myopathy, known as white muscle disease (WMD), in horses. However, correlations between Se deficiency and clinical findings, such as hematologic biochemical values and pathological features, have not been evaluated in captive plains zebras. The purpose of the present study was to investigate the clinical and pathologic features that may be caused by a Se deficiency in the captive plains zebra. Clinical findings, feed analyses, hematologic biochemical analyses, response to treatment, and pathologic examinat...
Dietary selenium and prolonged exercise alter gene expression and activity of antioxidant enzymes in equine skeletal muscle.
Journal of animal science    August 3, 2016   Volume 94, Issue 7 2867-2878 doi: 10.2527/jas.2016-0348
White SH, Johnson SE, Bobel JM, Warren LK.Untrained Thoroughbred horses (6 mares and 6 geldings; 11 yr [SE 1] and 565 kg [SE 11]) were used to evaluate antioxidant gene expression and enzyme activity in blood and skeletal muscle in response to prolonged exercise after receiving 2 levels of dietary selenium for 36 d: 0.1 (CON; = 6) or 0.3 mg/kg DM (SEL; = 6). Horses were individually fed 1.6% BW coastal bermudagrass hay, 0.4% BW whole oats, and a mineral/vitamin premix containing no Se. Sodium selenite was added to achieve either 0.1 or 0.3 mg Se/kg DM in the total diet. On d 35, horses underwent 2 h of submaximal exercise in a free-st...
Congenital nutritional myodegeneration in a neonatal foal.
The Canadian veterinary journal = La revue veterinaire canadienne    July 20, 2016   Volume 57, Issue 7 781-784 
MacQuarrie J.A 2-day-old Quarter Horse colt was presented to the Atlantic Veterinary College for recumbency and diarrhea. Dietary history of the dam, serum biochemistry findings, and whole blood selenium levels were consistent with nutritional myodegeneration. The patient was treated successfully with fluid therapy and broad-spectrum antimicrobials. Recovery was uneventful, and the patient was discharged with a favorable prognosis. Un poulain Quarter Horse âgé de deux jours a été présenté à l’Atlantic Veterinary College pour un décubitus et de la diarrhée. L’anamnèse nutritionnelle de la mè...
Acquired multiple acyl-CoA dehydrogenase deficiency and marked selenium deficiency causing severe rhabdomyolysis in a horse.
The Canadian veterinary journal = La revue veterinaire canadienne    November 6, 2015   Volume 56, Issue 11 1166-1171 
Gomez DE, Valberg SJ, Magdesian KG, Hanna PE, Lofstedt J.This report describes a case of severe rhabdomyolysis in a pregnant mare associated with histopathologic and biochemical features of both selenium deficiency and acquired multiple acyl-CoA dehydrogenase deficiency (MADD) due to seasonal pasture myopathy (SPM). This case highlights the importance of assessing plasma selenium levels in horses with clinical signs of pasture myopathy as this deficiency may be a contributing or exacerbating factor. Déficience multiple acquise de déshydrogénase acyl-CoA et carence en sélénium marquée causant une rhabdomyolyse grave chez un cheval. Ce rapport d...
HORSE SPECIES SYMPOSIUM: Nutritional programming and the impact on mare and foal performance.
Journal of animal science    October 7, 2015   Volume 93, Issue 7 3261-3267 doi: 10.2527/jas.2015-9057
Coverdale JA, Hammer CJ, Walter KW.Many environmental factors can alter the phenotype of offspring when applied during critical periods of early development. In most domestic species, maternal nutrition influences fetal development and the fetus is sensitive to the nutrition of the dam during pregnancy. Many experimental models have been explored including both under- and overnutrition of the dam. Both nutritional strategies have yielded potential consequences including altered glucose tolerance, pancreatic endocrine function, insulin sensitivity, body composition, and colostrum quality. Although the impact of maternal nutritio...
Blood and Cerebrospinal Fluid α-Tocopherol and Selenium Concentrations in Neonatal Foals with Neuroaxonal Dystrophy.
Journal of veterinary internal medicine    September 22, 2015   Volume 29, Issue 6 1667-1675 doi: 10.1111/jvim.13618
Finno CJ, Estell KE, Katzman S, Winfield L, Rendahl A, Textor J, Bannasch DL, Puschner B.Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on α-tocopherol (α-TP)-deficient diet. Objective: Intramuscular α-TP and selenium (Se) administration at 4 days of age would have no significant effect on serum or cerebrospinal fluid (CSF) α-TP in healthy foals. Serum and CSF α-TP, but not Se, would be significantly decreased in NAD/EDM-affected foals during first year of life. Methods: Fourteen Quarter horse foals; 10 healthy foals supplemented with 0.02 mL/kg injectable α-TP ...
Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.
Equine veterinary journal    September 17, 2015   Volume 47 Suppl 48 19 doi: 10.1111/evj.12486_43
van Loon G, Lefère L, Bauwens C, Kleyn K, Broux B, De Clercq D, Deprez P.Yellow fat disease or steatitis is characterised by a local or general inflammation of fat tissue and is occasionally found in horses. Diagnosis is challenging because of the wide range of nonspecific clinical signs. Objective: To describe clinical signs, treatment, outcome and ultrasonographic findings in horses with steatitis. Methods: Retrospective study (January 2008 to January 2015). Methods: History, clinical signs, ultrasonographic findings, diagnosis, treatment and outcome were recorded. Results: Twenty cases (18 horses, 2 donkeys; 9 mares, 9 stallions, 2 geldings) were retrieved from ...
Concentrations of strontium, barium, cadmium, copper, zinc, manganese, chromium, antimony, selenium and lead in the equine liver and kidneys.
SpringerPlus    July 8, 2014   Volume 3 343 doi: 10.1186/2193-1801-3-343
Paßlack N, Mainzer B, Lahrssen-Wiederholt M, Schafft H, Palavinskas R, Breithaupt A, Neumann K, Zentek J.The concentrations of specific elements in the equine liver and kidneys are of practical relevance since horses are not only food-producing animals, but also partially serve as an indicator for the environmental pollution, as the basic feed includes plants like grass, grain and fruits. In this study, the concentrations of strontium (Sr), barium (Ba), cadmium (Cd), copper (Cu), zinc (Zn), manganese (Mn), chromium (Cr), antimony (Sb), selenium (Se) and lead (Pb) were measured in the liver, renal cortex and renal medulla of 21 horses (8 male; 13 female; aged between 5 months-28 years), using indu...
Analysis in horse hair as a means of evaluating selenium toxicoses and long-term exposures.
Journal of agricultural and food chemistry    June 2, 2014   Volume 62, Issue 30 7393-7397 doi: 10.1021/jf500861p
Davis TZ, Stegelmeier BL, Hall JO.Horses are very susceptible to chronic selenosis if grazed on seleniferous forages for a prolonged period. In this study, mane and tail samples from horses that exhibited classical hoof lesions of chronic selenosis were analyzed by inductively coupled plasma mass spectrometry for selenium (Se) content. The horses had grazed for 6 months, from approximately May 15 until November 15, each year for three grazing seasons in a pasture containing seleniferous forages and water sources with elevated Se concentrations. The segmented hair samples showed a cyclic pattern in Se concentrations in the mane...
Serum selenium concentration and glutathione peroxidase activity and selenium content in testes of Polish Konik horses from selenium–deficient area in North-Western Poland.
Polish journal of veterinary sciences    April 15, 2014   Volume 17, Issue 1 165-167 doi: 10.2478/pjvs-2014-0022
Pilarczyk B, Tomza-Marciniak A, Stankiewicz T, Błaszczyk B, Gaczarzewicz D, Smugała M, Udała J, Tylkowska A, Kuba J, Cieśla A.The aim of this study was to determine serum selenium concentrations in Polish Konik horses residing in the Odra Delta Nature Park (Poland) and to evaluate the activity of glutathione peroxidase and Se content in testes of this horse breed. In over 95% of cases, serum Se concentration was below the optimal range, and none of the horses examined was deficient in this trace element. The lack of Se deficiency in the animals examined suggests however, that the Polish Konik horses have a natural ability to the optimal use of nutrients available in their life area. Testicular content of Se and GSHPx...
Effects of added chelated trace minerals, organic selenium, yeast culture, direct-fed microbials, and Yucca schidigera extract in horses. Part I: Blood nutrient concentration and digestibility.
Journal of animal science    August 3, 2013   Volume 91, Issue 8 3899-3908 doi: 10.2527/jas.2013-6122
Gordon ME, Edwards MS, Sweeney CR, Jerina ML.The objective of this study was to test the hypothesis that feed additives such as chelated minerals, organic Se, yeast culture, direct-fed microbials, and Yucca schidigera extract would improve nutrient digestibility when included in an equine diet. Horses (Quarter Horse geldings 4.5 to 16 yr of age; mean BW 522 kg ± 46 kg) were acclimated to 100% pelleted diets formulated with (ADD) and without (CTRL) commercially available sources of the aforementioned additives followed by a 14-d collection period of feces and urine. Chelated sources of Cu, Zn, Mn and Co were utilized versus sulfated form...
Effects of added chelated trace minerals, organic selenium, yeast culture, direct-fed microbials, and Yucca schidigera extract in horses: II. Nutrient excretion and potential environmental impact.
Journal of animal science    July 23, 2013   Volume 91, Issue 8 3909-3916 doi: 10.2527/jas.2012-6123
Gordon ME, Edwards MS, Sweeney CR, Jerina ML.The objective of this study was to test the hypothesis that an equine diet formulated with chelated trace minerals, organic selenium, yeast culture, direct-fed microbials (DFM) and Yucca schidigera extract would decrease excretion of nutrients that have potential for environmental impact. Horses were acclimated to 100% pelleted diets formulated with (ADD) and without (CTRL) the aforementioned additives. Chelated sources of Cu, Zn, Mn, and Co were included in the ADD diet at a 100% replacement rate of sulfate forms used in the CTRL diet. Additionally, the ADD diet included organic selenium yeas...
The effect of selenium supplementation on vaccination response and immune function in adult horses.
Journal of animal science    May 8, 2013   Volume 91, Issue 8 3702-3715 doi: 10.2527/jas.2012-5819
Brummer M, Hayes S, Adams AA, Horohov DW, Dawson KA, Lawrence LM.Selenium status has been reported to affect immune function across many different species. Yet few studies have focused on the effect of Se status on the equine immune system. This study examined the effect of Se supplementation on vaccination response and immune function in mature horses. Twenty-eight horses were blocked by age and sex and were randomly allocated to 1 of 4 dietary treatment groups: low Se (LS), adequate Se (AS), Se-yeast (SP), and sodium selenite (SS). For 35 wk, horses allocated to LS, SP, and SS received a low-Se diet (0.06 mg/kg DM) with the intention to lower Se stores, w...
Effects of selenium source on measures of selenium status and immune function in horses. Montgomery JB, Wichtel JJ, Wichtel MG, McNiven MA, McClure JT, Markham F, Horohov DW.The effects of selenium (Se) supplementation and source on equine immune function have not been extensively studied. This study examined the effects of oral Se supplementation and Se source on aspects of innate and adaptive immunity in horses. Fifteen horses were assigned to 1 of 3 groups (5 horses/group): control, inorganic Se (sodium selenite), organic Se (Se yeast). Immune function tests performed included: lymphocyte proliferation in response to mitogen concanavalin A, neutrophil phagocytosis, antibody production after rabies vaccination, relative cytokine gene expression in stimulated lym...
Effect of selenium and vitamin C on clinical outcomes, trace element status, and antioxidant enzyme activity in horses with acute and chronic lower airway disease. A randomized clinical trial.
Biological trace element research    March 13, 2013   Volume 152, Issue 3 333-342 doi: 10.1007/s12011-013-9636-5
Youssef MA, El-khodery SA, Ibrahim HM.Excess production of reactive oxygen species is involved in the pathogenesis of airway disorders in horses. Trace element antioxidants have a beneficial role in oxidant/antioxidant balance. The aim of the present study was to evaluate the effect of a combination of sodium selenite and ascorbic acid on clinical outcome, antioxidant enzymes, and trace elements status in horses with lower airway disease. For this purpose, 40 draft horses with lower airway disease were randomly selected (acute, n = 20; chronic, n = 20). Both acute and chronic cases were randomly allocated into two subgroup...
Measures of antioxidant status of the horse in response to selenium depletion and repletion.
Journal of animal science    March 5, 2013   Volume 91, Issue 5 2158-2168 doi: 10.2527/jas.2012-5794
Brummer M, Hayes S, Dawson KA, Lawrence LM.Selenium plays a role in the antioxidant mechanism via the selenoenzyme glutathione peroxidase (GSH-Px). Change in Se status because of Se depletion or supplementation is associated with a change in GSH-Px activity and could potentially affect antioxidant status. This study evaluated the impact of change in Se status on measures of antioxidant status and oxidative stress in adult horses. Twenty-eight horses were blocked by age and gender and were randomly allocated to 1 of 4 dietary treatment groups: low Se (LS), adequate Se (AS), high organic Se (SP), and high inorganic Se (SS). For 196 d, LS...