Selenium and vitamin E effect on antibody production of sheep vaccinated against enzootic abortion (Chlamydia psittaci)

The effect of selenium (Se) and vitamin E (vit E) on antibody production of sheep vaccinated against Chlamydia psittaci (ovis) was investigated. Thirty-two sheep, one year old, seronegative to Chlamydia infection, vaccinated against enterotoxemia and dewormed were used. Injectable sodium selenite (0.1 mg/kg b.w.) was given twice to animals of the first group (gSe), with a three week interval. The sheep of the second group (gE) received 1 g vit E each orally, six times at weekly intervals. The animals of the third group (gSeE) were given Se and vit E in doses and routes of administration as in gSe and gE. The animals of the fourth group served as controls (gC) and injected normal saline. The first vaccination was made at the time that the second Se injection was given. Revaccination was made two weeks later. The experiment lasted 29 weeks. The results indicated that Se alone led to a significant increase of Chlamydia antibody response (P < 0.05), but not when it was given in combination with vit E. Animals that received vit E (gE) had much lower titres, just above of those of the controls.     

Vitamin E and selenium concentrations in month-old beef calves.

Three groups of beef cow and calf pairs were studied to determine plasma vitamin E and blood selenium (Se) concentrations of calves at 1 month old. Group 1 was managed on irrigated pasture and calves received no Se/vitamin E injections at birth. Group 2 was managed on irrigated pasture, and the calves were injected with Se/vitamin E at birth. Group 3 was managed on dry foothill grasslands, and these cows were supplemented with 56.3 mg vitamin E and 3 mg Se daily, and the calves received a Se/vitamin E injection at birth. The plasma concentration of vitamin E in group 1 and 2 cows (9.5 +/- 1.24 and 8.43 +/- 1.0 microg/ml, respectively) was significantly higher than that of the group 3 cows (2.28 +/- 0.42 microg/ml; P < 0.05). The blood Se concentrations in group 3 cows (169 +/- 37 ng/ml) were significantly higher than those in group 1 and 2 cows (36.4 +/- 15.9 and 31.1 +/- 12.5 ng/ml, respectively; P < 0.05). Calf Se was highly correlated to cow Se (r = 0.965), and calf vitamin E was moderately correlated to cow vitamin E (r = 0.605). Calf vitamin E concentrations were consistently lower than cow vitamin E concentrations, and many values would be considered deficient.     

Effects of vitamin E and selenium supplementation on blood lipid peroxidation and cortisol concentration in dairy cows undergoing omentopexy

Twenty dairy cows with left abomasal displacement were used to investigate the effects of vitamin E and selenium treatment on thiobarbituric acid reactive substances (TBARS) and blood cortisol in dairy cows stressed by omentopexy. The cows were randomly divided into two groups. Ten hours before surgery 6 g of DL‐α‐tocopheryl acetate (6 mg/kg) and 67 mg of natrium selenite (0.1 mg/kg) in volume of 40 ml (Vitaselen^®) were administered subcutaneously to 10 cows; the control animals (n = 10) received an equivalent volume of injectable water (40 ml). The injection of vitamin E and selenium produced a rapid rise (p < .05) in blood α‐tocopherol and selenium concentrations. The serum vitamin E increased several times 10 hr after vitamin E and Se injection and raised continuously to the highest average concentration 21.6 mg/L at hr 24 after the surgery. The highest selenium concentration was seen 10 hr after selenium administration with holding the increased concentrations in comparison with initial ones during the whole study. Two‐way ANOVA did not show significant treatment effect on plasma concentrations TBARS in the study. The plasma concentrations of thiobarbituric acid reactive substances reached the maximum value of 0.18 μmol/L in the control group 5 hr after the surgery. Twenty‐four hours after the surgery, the TBARS values returned to the initial ones. Serum cortisol increased in both groups after surgery. The highest cortisol concentrations were reached at 1 hr after surgery in the experimental and control group (56.7 ± 28.8 and 65.3 ± 26.1 μg/L respectively). A return to the levels similar to the initial ones was recognized 24 hr after the surgery. The ANOVA revealed a significant effect of vitamin E and selenium injection on plasma cortisol (p < .05). In conclusion, we have demonstrated that abdominal surgery resulted in typical stress changes with no significant effects of a single vitamin E/Se injection on blood lipid peroxidation. In addition, a weaker cortisol response to the abdominal surgery was recognized in animals treated with vitamin E and selenium.     

Effect of supplementation of vitamin E, selenium and their different combinations on the performance and immune response of broilers

1. The effect of dietary vitamin E, selenium (Se) and their different combinations on body weight gain, food consumption, food conversion efficiency, leukocyte migration inhibition and antibody production was determined in broilers. 2. Chicks were fed on maize-soya bean based diets with concentrations of supplemental vitamin E varying from 0 to 300 IU/kg and selenium concentrations varying from 0 to 1 mg/kg either alone or in combination from 1 to 42 d of age. 3. The chicks were immunised for Newcastle Disease Virus (NDV) vaccine at 21 d. Per cent leukocyte migration inhibition (LMI) was studied on 42 d. Antibodies to NDV in serum were determined at 10 and 21 d post immunisation (PI). 4. Chicks receiving Se, 1 mg/kg and vitamin E 300 IU/kg had significantly higher cellular immune responses in terms of per cent LMI. 5. Maximum body weight gain and best efficiency of food utilisation were obtained in chicks fed diets containing 0.50 mg/kg Se and 300 IU/kg vitamin E. 6. Significantly higher antibody titres (HI and ELISA) at 10 d PI were attributed to 0.06 mg/kg and 150 IU/kg Se and vitamin E, respectively. 7. These data suggest that optimum growth and immune response may be achieved at supplemental level of Se of 0.06 mg/kg and vitamin E at 150 IU/kg. The vitamin E level is higher than that recommended by NRC (1984, 1994).     

硒与维生素E对鸡马杜霉素急性中毒的保护作用

在实验条件下用7mg/kg bw.剂量的马杜霉不诱发鸡急性中毒，处理组鸡在给马杜霉素前给予硒（0.2mg/kg bw.剂量，内服）－维生素E（每kg饲料含200mg)7d，在给马杜霉素后给予硒（0.2mg/kg bw.剂量，内服）－维生素E（200mg/kg bw.剂量，肌注）4d，中毒组在给马杜霉素前后不给任何硒和维生素E，对照组既不给马杜霉素，也不给硒与维生素E。结果是：处理组鸡的死亡率显著低于中毒组（P＜0.05），且病鸡恢复比中毒组快。处理组的肝脏、心肌、骨骼肌的出血与变性比中毒组轻，但处理组与中毒组的肾脏的出血与变性的程度相似；处理组的血清GOT值、肝脏的脂质过氧化物的含量、肝脏过氧化氢酶的性均显著低于中毒组；但处理组的血清CK值与中毒组相比无显著性差异。结果表明硒与维生素E对鸡马杜霉素急性中毒有较好的保护作用。     

Effects of supplemental parenteral administration of vitamin E and selenium to Jerseys and Holsteins during the nonlactating period

OBJECTIVE: To determine effects of breed and supplemental administration of vitamin E and selenium (Se) during late gestation on circulating concentrations of these micronutrients in periparturient Jerseys and Holsteins. DESIGN: Randomized controlled clinical study. ANIMALS: 16 Jersey and 36 Holstein cows. PROCEDURE: Cows were allotted to blocks on the basis of breed and expected parturition date. Cows within blocks were randomly assigned to be given vitamin E or Se parenterally 3 to 4 weeks prior to anticipated parturition in a 2 x 2 factorial design. RESULTS: Results of ANOVA indicated Jerseys had higher blood concentrations of Se and lower serum concentrations of vitamin E than Holsteins at the end of lactation. Jerseys had higher blood concentrations of Se than Holsteins 3 to 4 weeks prior to parturition and at parturition. Selenium administration increased blood concentrations of Se at parturition. Administration of nutrients did not affect serum concentrations of vitamin E at parturition or 2 to 3 weeks after parturition or blood concentrations of Se 2 to 3 weeks after parturition. CONCLUSIONS AND CLINICAL RELEVANCE: Jerseys and Holsteins consuming rations of comparable Se content differ in blood concentrations of Se during the nonlactating period, suggesting breed-related differences in Se metabolism during late lactation and the nonlactating period. Parenteral administration of Se 3 to 4 weeks prior to anticipated parturition increased blood concentrations of Se at parturition; however, Se concentrations of both groups at parturition were considered within the reference range for clinically normal cattle.     

Effects of Selenium Administration on Erythrocyte and Blood Plasma Glutathione Peroxidase Activity in Goats

The activity of glutathione peroxidase (GSH-Px, E.G. 1.11.1.9.) was determined in heparinized whole blood, blood plasma and washed erythrocytes from goats before and up to 4 weeks after the administration of selenium (0.4 mg/10 kg BW) and vitamin E (20 mg/10 kg BW) or only vit. E (20 mg/10 kg BW). It was found that Se administration caused a significant increase in enzyme activity in whole blood and washed erythrocytes first detected 2 weeks after the intramuscular injection of Se. No changes were observed in plasma from the treated animals. Minor and insignificant changes were seen in the vit. E treated control animals. It is concluded that GSH-Px activity in blood plasma or serum is of no value as a short-term indicator of the selenium status of goats but whole blood is a good indicator of the long-term status.     

Influence of vitamin E and selenium supplement on antibody production in horses

Fifteen horses used for serum production were maintained on low vitamin E and selenium diets. They were divided into four groups receiving: Group 1 no supplements, Group 2 vitamin E, Group 3 selenium and Group 4 both vitamin E and selenium. The humoral immune response to novel antigens, such as tetanus toxoid and equine influenza virus, was increased in groups receiving either vitamin E or selenium/vitamin E. No effects were recorded on the titres against Escherichia coli or the levels of immunoglobulin G.     

Effects of dietary supplements of selenium, vitamin E or combinations of the two on antibody responses of broilers

1. The effects of selenium and vitamin E supplementation on some immune parameters were investigated in broilers. 2. Broiler chicks were fed on maize-soybean diets with different concentrations of vitamin E (0-200 mg/kg) and selenium (0-0.2 mg/kg diet) either alone or in combinations from 1 to 42 d of age. 3. Chicks were immunised against Newcastle disease virus (NDV) vaccine at 21 d of age and haemagglutination inhibition (HI) titres were determined after 10 d. 4. Chicks receiving supplements of 200 mg vitamin E/kg and 0.2 mg selenium/kg produced significantly higher HI antibody titres. This was associated with an increased serum concentration of total immunoglobulins and circulatory immune complexes. 5. The chicks given 200 mg vitamin E/kg and 0.2 mg selenium/kg had significantly heavier spleen and bursa. 6. These results suggested that vitamin E and selenium have synergistic effects on immune responses.     

Parenteral selenium and vitamin E supplementation of weaned beef calves

BACKGROUND: The weaning process in beef calves elicits physiological stress responses that can negatively affect performance and health. Supplementation of vitamins and minerals, particularly selenium (Se) and vitamin E, might be warranted. HYPOTHESIS: That parenteral administration of Se or vitamin E would correct or prevent deficiencies of these nutrients in postweaned beef calves during a backgrounding period (42 days after weaning). ANIMALS: One hundred and forty-four weaned steers (200-250 kg) in 3 trials. METHODS: One trial was conducted with cattle on a dry lot fed a total mixed ration and 2 trials were conducted on cattle on pasture. Selenium was administered at 0.05 mg/kg BW (SC) and vitamin E was administered at 1500 IU on days 0 and 28 (SC). RESULTS: A treatment effect attributable to Se or vitamin E supplementation on average daily gain was not detected in any trials. Parenteral supplementation with Se on days 0 and 28 resulted in higher serum Se concentrations as compared with controls on day 42. Parenteral supplementation with Se on days 0 and 28 improved Se status from marginal to adequate in 1 trial. Parenteral supplementation with vitamin E did not improve serum vitamin E concentrations in any experiment. CONCLUSIONS AND CLINICAL IMPORTANCE: Supplementation with vitamin E or Se or a combination of both did not have a significant effect on calf performance during the 42-day backgrounding period.     

Blood and milk status of vitamin E,vitamin A,and selenium in nursing Awassi ewes injected with vitamin E and selenium

Abstract

This study investigated the effects of vitamin E and selenium (Se) injections on concentrations of vitamin E, vitamin A, and Se in blood and milk to predict when injections may improve ewes’ performance. Awassi ewes received 0 (control, 13 ewes) or 15 plus 0.05?mg/kg BW of vitamin E and Se (injected, 15 ewes) at 1 and 4 weeks postpartum. Blood and milk samples were collected weekly for 6 weeks. Injections increased vitamin E, decreased Se, and had no effects on vitamin A levels in blood. Blood vitamin E was correlated positively with vitamin A. Injections increased vitamin E, but had no effects on vitamin A or Se levels in milk. Milk vitamin A was positively correlated with vitamin E and Se levels in the control group. Milk vitamins E and A were positively correlated with their corresponding levels in blood. Milk somatic cell count was negatively correlated with blood vitamin A levels.     

Comparative toxicosis of sodium selenite and selenomethionine in lambs.

Excess consumption of selenium (Se) accumulator plants can result in selenium intoxication. The objective of the study reported here was to compare the acute toxicosis caused by organic selenium (selenomethionine) found in plants with that caused by the supplemental, inorganic form of selenium (sodium selenite). Lambs were orally administered a single dose of selenium as either sodium selenite or selenomethionine and were monitored for 7 days, after which they were euthanized and necropsied. Twelve randomly assigned treatment groups consisted of animals given 0, 1, 2, 3, or 4 mg of Se/kg of body weight as sodium selenite, or 0, 1, 2, 3, 4, 6, or 8 mg of Se/kg as selenomethionine. Sodium selenite at dosages of 2, 3, and 4 mg/kg, as well as selenomethionine at dosages of 4, 6, and 8 mg/kg resulted in tachypnea and/or respiratory distress following minimal exercise. Severity and time to recovery varied, and were dose dependent. Major histopathologic findings in animals of the high-dose groups included multifocal myocardial necrosis and pulmonary alveolar vasculitis with pulmonary edema and hemorrhage. Analysis of liver, kidney cortex, heart, blood, and serum revealed linear, dose-dependent increases in selenium concentration. However, tissue selenium concentration in selenomethionine-treated lambs were significantly greater than that in lambs treated with equivalent doses of sodium selenite. To estimate the oxidative effects of these selenium compounds in vivo, liver vitamin E concentration also was measured. Sodium selenite, but not selenomethionine administration resulted in decreased liver vitamin E concentration. Results of this study indicate that the chemical form of the ingested Se must be known to adequately interpret tissue, blood, and serum Se concentrations.     

Glutathione Peroxidase Activity and Erythrocyte Lipid Peroxidation as Indices of Selenium and Vitamin E Status in Young Pigs

A randomized, blocked 2³ factorial experiment was conducted with 48 pigs from sows fed a diet low in selenium and vitamin E. From 3 to 12 weeks of age the piglets were kept in single pens and fed a basic diet consisting mostly of barley, dried skim milk, soybean meal and dried yeast, and containing 55 µg selenium and 3 mg vitamin E per kg. The treatment factors — i.e. feed supplements — were 2 levels of Se (nil, 60 µg/kg), 2 levels of vitamin E (nil, 50 mg/kg), and 2 levels of the feed antioxidant ethoxyquin (nil, 150 mg/kg). Blood samples, collected at termination of the experiment, were examined for glutathione peroxidase activity (GSH-Px) and resistance against erythrocyte lipid peroxidation (ELP) to evaluate Se and vitamin E status, respectively. Analysis of variance showed the GSH-Px activity to be litter-dependent (P < 0.001) and influenced by selenium supplementation (P < 0.001) but not by the other supplements or by interactions between supplements. Resistance against ELP was influenced only by vitamin E supplementation (P < 0.001). GSH-Px and ELP thus seem to be valuable and simple methods for evaluating, respectively, Se status and vitamin E status in growing pigs.     

Effect of grazing pasture with a low selenium content on the concentrations of triiodothyronine and thyroxine in serum, and GSH-Px activity in erythrocytes in cows in Chile

AIM: To determine the effect of grazing pasture that had a low selenium (Se) concentration on serum concentrations of triiodothyronine (T3) and thyroxine (T4), and erythrocyte glutathione peroxidase (GSH-Px) activity in dairy cows. METHODS: Forty pregnant Friesian cows were grazed on pasture that contained 0.03-0.04 ppm Se on a dry matter (DM) basis. Two months before parturition, 20 cows were randomly selected and treated with 1 mg Se/kg bodyweight subcutaneously, as barium selenate (Group Se-S). The other group (Se-D) was not supplemented. Blood samples were taken before supplementation (-60 days) and 30, 60, 90, 180 and 270 days after parturition, for determination of concentrations of T3 and T4 in serum, and GSH-Px activity in erythrocytes. RESULTS: Erythrocyte GSH-Px activity in the Se-D group was <60 U/g haemoglobin (Hb) throughout the experiment. Supplementation increased (p<0.05) activities to >130 U/g Hb throughout lactation. Mean serum concentrations of T4 in Se-D and Se-S cows increased from 23.7 (SEM 0.7) and 23.4 (SEM 0.8) nmol/L, respectively, in the prepartum period to 69.6 (SEM 0.1) and 67.6 (SEM 0.2) nmol/L, respectively, at 180 days of lactation (p<0.01), and no effect of Se supplementation was evident. Serum concentrations of T3 in Se-D cows decreased (p<0.05) from 1.6 (SEM 0.1) nmol/L prepartum to 1.0 (SEM 0.2) nmol/L at the beginning of lactation, and remained lower (p<0.05) than those in the Se-S cows which did not decrease after calving and ranged from 1.9 (SEM 0.1) to 2.4 (SEM 0.2) nmol/L throughout lactation. CONCLUSIONS: Serum T3 concentrations decreased during early lactation in unsupplemented cows grazing pastures low in Se (0.03-0.04 ppm) and both serum T3 and erythrocyte GSHPx activities were consistently lower throughout lactation compared with Se-supplemented cows. Se supplementation had no effect on serum T4 concentrations.     

Efficacy of vitamin E + selenium and vitamin A + D + E combinations on oxidative stress induced by long-term transportation in Holstein dairy cows

The aim of this study was to evaluate the stress response to long-term transportation and to analyze the effects of vitamin A + D + E and vitamin E + selenium administrations on oxidative stress induced by long-term transportation in Holstein dairy cows. Control group (n = 10) received 0.9% saline (placebo), Group I (n = 10) received vitamin A + D + E, and Group II (n = 10) received vitamin E + selenium. After the transport, adrenaline levels were high in all groups (P < 0.05). Noradrenaline level was low in Group I (P < 0.05) and tended to be low in Group II. Mean levels of serum cortisol decreased significantly in all groups (P < 0.05) when comparing pre-transport data with post-transport data. Glucose levels increased in Control group (P < 0.05) and in Groups I and II (P < 0.01). The malondialdehyde level significantly increased in the Control group (P < 0.05) after the transport and the levels were lower in Group I (P = 0.076) and Group II (P < 0.05) than in the Control group. As a result, vitamin E + selenium and vitamin A + D + E have been determined to prevent lipid peroxidation and oxidative stress, associated with long-term transportation stress in cattle.     

Selenium and vitamin E in blood sera of cows from farms with increased incidence of disease

Selenium and vitamin E concentrations were measured in the blood sera of 287 cows in 91 herds. Herds with chronic mastitis and muscle diseases had significantly lower selenium concentrations (10.4 +/- 5.26 and 11.7 +/- 8.63 micrograms/litre serum, respectively) than healthy control herds (17.7 +/- 15.00 micrograms/litre). The selenium concentrations in herds with low fertility did not differ from control herds. The vitamin E concentrations were similar in all the herds. Supplementation of the mineral mixture with 20 mg sodium selenite and 2 g vitamin E/kg on 15 farms with a deficient selenium supply increased the selenium concentrations in the blood within two months in 12 of the herds. The vitamin E concentrations were hardly influenced by the supplementation.     

A Protective Effect of Vitamin E and Selenium in Ameliorating the Immunotoxicity of Malathion in Chicks

A study was conducted to determine whether a combination of vitamin E and selenium was able to counteract the immunosuppressive effects of chronic toxicity of malathion in chicks. The chicks were divided into three groups. The first group received malathion 10 mg/kg body weight; the second group received the same dose of malathion but was supplemented with vitamin E and selenium for 60 days; and the third group served as the control. The concentration of total immunoglobulins and circulatory immune complexes decreased following the administration of malathion, whereas the supplementation of the diet with vitamin E and selenium partially counteracted this effect. The histopathological changes in the bursa of Fabricius due to malathion were consistent with these findings. Supplementation with vitamin E and selenium partially ameliorated the degenerative changes in the bursa of Fabricius. Sodhi, S., Sharma, A. and Brar, R.S., 2006. A protective effect of vitamin E and selenium in ameliorating the immunotoxicity of malathion in chicks. Veterinary Research Communications, 30(8), 935–942     

Effectiveness of α-tocopherol and selenium supplements in preventing lupinosis-associated myopathy in sheep

Objective To compare the effectiveness of combined selenium and α-tocopherol acetate treatments in preventing lupinosis-associated myopathy in sheep.
Design Measurement of plasma muscle and liver enzymes, and histopathological examination of muscle and liver in the treatment groups.
Procedure The treatments were: subcutaneous injections of selenomethionine and vitamin E (sc(SeM+E)) , an intraruminal selenium pellet and oral doses of vitamin E and intramuscular injections of selenomethionine combined with either oral doses of vitamin E (imSeM+orE) or intramuscular injections of vitamin E in an oily carrier. Another group received no supplements, while a control group was given selenium pellets on day 0 and fortnightly oral doses of vitamin E from day 0 to 72. To produce lupinosis-associated myopathy, the sheep were fed a diet low in vitamin E and given repeated injections of a crude extract of Diaphorthe toxica. Groups sc(SeM+E) and imSeM+orE were stressed by dosing with protected polyunsaturated fatty acids from day 56 onwards.
Results Lupinosis-associated myopathy was induced in all unsupplemented sheep. In these sheep the storage of Se increased and that of vitamin E decreased. The subcutaneous treatment was highly effective in preventing lupinosis-associated myopathy and also produced the highest vitamin E concentrations in plasma and liver. Supplemental vitamin E was more efficacious than supplemental Se. Concentrations of vitamin E in the livers of sheep given intramuscular vitamin E were higher than expected based on plasma concentrations. Oral doses of vitamin E proved the least effective method of increasing concentrations in liver. Lupinosis did not affect Se concentrations in liver or muscle.
Conclusion The sc(SeM+E) treatment is highly effective in preventing lupinosis-associated myopathy but needs to be further assessed when selenium and vitamin E are both limiting in the diet.     

硒和维生素E在硒缺乏动物自由基代谢中作用机制的研究

为阐明硒缺乏动物自由基代谢与硒缺乏症发病学的关系，以及硒和ＶＥ在自由基代谢中的作用采用低Ｓｅ日粮饲喂小鼠，并对血液、肝组织丙二醛、硒谷胱甘肽过氧化物酶、相关向量元素及自由基水平进行了系统检测。     

Dietary vitamin E (alpha-tocopherol acetate) and selenium supplementation from different sources: performance, ascites-related variables and antioxidant status in broilers reared at low and optimum temperatures

1. This study compared the effect of dietary supplementation with organic or inorganic selenium (Se) sources plus control amounts or large amounts of vitamin E (alpha-tocopherol acetate) in broilers raised at control (20 to 24 degrees C) or low (14.5 to 16.8 degrees C) temperatures after 2 weeks of age. 2. The following dietary treatments were used from one day old. Diet 1, the control diet, comprised a commercial diet containing 0.15 mg/kg inorganic Se and 50 mg vitamin E/kg feed. Diet 2 was the same as diet 1, supplemented with 0.15 mg/kg inorganic Se. Diet 3 was the same as diet 2 but was supplemented with 200 mg/kg vitamin E. Diet 4 was the same as diet 1, but inorganic Se was replaced with 0.30 mg/kg organic Se. Diet 5 was the same as diet 4, supplemented with 200 mg/kg vitamin E. 3. Low temperature reduced the growth rate of broilers; however, at 6 weeks, there were no differences in the body weights of birds fed on organic Se supplemented diets housed at low or control temperature. The feed conversion ratio was significantly affected by low temperature but not by diet. The heterophil/lymphocyte ratio was higher in chicks after one week in the cold, indicating mild stress. Blood triiodothyronine levels were significantly higher in birds after 1 and 4 weeks in the cold but thyroxin was not affected. 4. Organic Se supplementation increased relative lung weight at the control temperature, which might lead to greater respiratory capacity. Relative spleen weight significantly decreased in broilers fed diets supplemented with inorganic Se under cold conditions, a possible indication of chronic oxidative stress. 5. At the low temperature, supplementation with organic Se alone, or with inorganic Se and vitamin E increased glutathione peroxidase (GSHPx) activity and glutathione (GSH) concentration in the liver of broilers, which may indicate increased activity of birds' antioxidant defence against suboptimal environments.