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Effects of selenium on animal health

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Selenium is an essential trace element in the diet of humans and domesticated animals. It is a component of more than 30 selenoproteins, which play a significant role in the body. Selenoproteins protect cells from damage inflicted by free radicals, the cause of many chronic diseases. They also participate in the metabolism of thyroid hormones, control reproductive functions and exert neuroprotective effects. In addition to its anti-proliferative and anti-inflammatory properties, selenium stimulates the immune system. The role of selenium is aided by vitamin E and sulfur-containing amino acids. Selenium deficiency contributes to pathological changes in farm animals, which incur large financial losses each year. Low selenium levels can lead to the development of nutritional muscular dystrophy, also known as white muscle disease, in lambs, kids, foals, calves and poultry from birth to 3 months of age. Selenium deficiency may also cause exudative diathesis in poultry as well as dietary necrotic liver degeneration and mulberry heart disease in pigs. Parturition problems resulting from reduced tension of the muscular layer of the uterus, postparturient paraplegia, placental retention and purulent inflammations of the uterine lining are also attributed to low selenium levels. Selenium deficiency contributes to the formation of ovarian cysts and increased embryonic mortality in the first 3-4 weeks after insemination. Selenium and vitamin E facilitate neutrophil migration to the mammary gland, and they enhance the bactericidal effects of neutrophils, thus shortening and alleviating the symptoms of clinical mastitis. Selenium poisoning is rarely encountered, and it most often results from an overdose of selenium supplements. The most common forms of selenosis are chronic selenosis, referred to as alkali disease, and acute selenosis, popularly known as blind staggers.
Similarly to the production of red blood cells, the production and development of leukocytes takes place in the bone marrow in the process of hematopoiesis. The key stages in the development of leukocytic cell lines are: neutrophilic, eosinophilic and basophilic granulopoiesis, monocytopoiesis, lymphopoiesis and megakaryopoiesis. Leukocytes produced at various developmental stages are characterized by differently shaped nuclei, the presence or absence of nucleoli, and variations in cytoplasm staining. The experiment was carried out on 10 clinically healthy HF cows. Bone marrow aspirate smears stained by the MGG method were analyzed. The study found significant differences in the number, size, and staining intensity of individual myeloid cell lines.
Selenium is an essential nutrient, which is crucial for proper body function. Its role is complemented by vitamin E. Nutritional muscular dystrophy (NMD) is one of the main disorders caused by a selenium deficiency. NMD most often affects calves at the age of 4 to 6 weeks. The study was performed on 40 Holstein-Friesian (HF) calves divided into two groups of 20 animals each. Control group calves were administered an IM injection of selenium and vitamin E on the second day of life. The experimental group comprised calves with symptoms of NMD. Samples of the biceps femoris muscle were collected from six animals in each group for histopathological analyses to confirm changes in muscle parameters. Blood samples were obtained from all animals on three different dates. The following blood parameters were determined in laboratory analyses: pH, pCO 2 , pO 2 , HCO 3 – , BE, O 2 SAT, the concentrations of Na + , K + , Cl – , and Ca and P levels. A drop in pH, an increase in the partial pressure of carbon dioxide, a decrease in the partial pressure of oxygen, a significant decrease in bicarbonate ion concentrations and hemoglobin oxygen saturation as well as a base deficit were reported in the group of calves demonstrating symptoms of NMD. The above changes point to the development of uncompensated metabolic acidosis due to increased levels of pyruvic acid and lactic acid produced as a result of anaerobic processes that accompany muscle fiber degeneration. Minor fluctuations in sodium and chloride levels were observed throughout the experiment, but their concentrations remained within the norm in animal groups. Potassium levels were significantly higher in the experimental group than in the control group. The serum concentrations of inorganic phosphorus and calcium were within the reference range in both groups. In calves, NMD leads to disruptions in the acid-base equilibrium and the electrolyte balance, which are manifested by uncompensated metabolic acidosis and hyperkalemia. Significant changes in calcium and phosphorus levels are not observed in the blood serum of calves affected by NMD.
Bone marrow examinations were performed in a group of 10 Holstein-Friesian (HF) cows aged 2 years, which had been diagnosed with BVD/MD infection in a PCR screening test. Prior to bone marrow sampling, peripheral blood samples were collected for hematological analysis. Bone marrow was sampled from the third and fourth ribs in the sternal region, and it was placed in test tubes containing no anticoagulant. Smears were stained by the MGG method. The aim of this study was to demonstrate changes in the process of hematopoiesis in animals with clinical signs of BVD/MD. The results of the analysis revealed changes in erythrocyte, macrocyte-macrophage, lymphoid and granulocytic cell lines. There was a decrease in the number of red blood cells in the peripheral blood and polychromatic and ortochromatic erythroblasts in the bone marrow. A decrease in leukocyte counts below reference values resulted mainly from a decrease in the number of neutrophilic metamyelocytes, eosinophilic myelocytes and banded eosinophils. Moreover, a decrease in the number of megakaryocytes was observed in the megakariocytic system. BVDV infection causes changes in the activity of the hematopoietic system.
The aim of this study was to determine the presence of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) neurons and co-localisation of CART with vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (n-NOS), vasoactive intestinal polypeptide (VIP), substance P (SP) and leu-enkephalin (LENK) in the enteric nervous system of the porcine gastric cardia by using a double-labelling immunofluorescence technique. CART-LI neurons were observed in the myenteric plexus (18.2}2.6%). A dense network of CART-LI nerve fibers was mainly observed in the muscular layer. CART showed co-localization mainly with VAChT, n-NOS, VIP and to a lesser degree with LENK and SP. Distribution of CART and its co- ocalization with other neurotransmitters suggest that this peptide plays an important role in gastric motility in the pig.
The aim of the study was to determine the activity and effectiveness of bone marrow hematopoiesis in healthy, adult cattle, and to compare hematopoietic activity levels in diseased cattle. The experimental material comprised 10 high-yielding, clinically healthy Holstein-Friesian cows aged 2-3 years. Bone marrow aspirate smears were analyzed. Marrow samples were collected with a marrow biopsy needle with a length of 63 mm (13G, from the medullary cavity of the third and fourth rib in the sternal region, and the material was subjected to a smear test. Marrow and peripheral blood smears were stained by a method proposed by May Grünwald-Giemsa (MGG). An increase in the number of orthochromatic erythroblasts with a simultaneous decrease in basophilic and polychromatic erythroblast counts was noted in this study. The results indicate that the nucleoli of bovine proerythroblasts are less visible, and the cytoplasm is stained light blue.
The purpose of this study was to investigate possible alterations in acid-base balance parameters and the coagulation profile in neonatal diarrheic calves. Twenty neonatal diarrheic and 20 clinically healthy neonatal calves aged between 1 week to 10 days were used. All blood samples were taken on the third day from the onset of diarrhea symptom. Venous blood samples were collected from each animal to determine platelet numbers, pH, pCO₂, pO₂, HCO₃⁻, BE, O₂SAT, ctCO₂ and electrolytes (K⁺, Na⁺ and Cl⁻). Plasma samples were collected from each animal for the measurement of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), the concentrations of fibrinogen, D-dimer and the activity of antithrombin III (AT III). Blood pH (7.19), BE (-10.6 mmol/l), HCO₃⁻ (25.15 mmol/l), pO₂ (3.33 kPa), O₂SAT (24.12 %) were significantly lower and serum concentration of K⁺ (6.55 mmol/l) was significantly higher in diarrheic calves. These changes indicate the state of uncompensated metabolic acidosis with accompanying hyperkalemia. TT (32.05s) and APTT (39.9s) values were more prolonged in calves with diarrhea than in the control group. D-dimer (587.25 μg/l) concentrations were significantly increased while a visible drop in AT III (103.75%) activity and platelets counts (598 x10⁹/l) were observed in diarrheic group of calves. The results suggest that a consumptive type of disseminated intravascular coagulation (DIC) developed in diarrheic calves.
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