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Сельскохозяйственная биология, 2010, № 2, с. 65-70.

УДК 636.3.033:636.087.72:57.017.32:591.111.1

BIOCHEMICAL AND PHYSIOLOGICAL STATUS OF LAMBS IN EARLY POSTNATAL ONTOGENESIS AGAINST THE BACKGROUND OF SELENIUM COMPOUNDS INJECTIONS TO EWE IN YEAN

G.I. Boryaev¹, I.V. Gavryushina¹, Yu.N. Fedorov²

The authors have made a comparative estimation of dynamics of Se content, activity of antioxidant protection enzymes and also hemoglobin amount in lambs’ blood, as result of introduction into organism of their mothers of 2 weeks before lambing of non-organic form selenium compound — Na₂SeO₃ and organic form — selenopyran. The obtained data let maintain that the strongest influ-ence on the blood index has selenopyran.

Key words: selenium compounds, lamb, ewe, colostrums, blood, ferments of antioxidant protection, glutation peroxydasa, superoxid dismutasa, hemoglobin, albumin.

 

At present time, the reproduction of farm animals and survival rate of youth are considered as a complex problem. The immunological status of a newborn animal is influenced by external environment and the state of maternal organism both.
The main damaging factor in stress reactions is a non-specific elevation of free radical processes, and its optimization can ensure the better adaptation of animals. Selenium compounds lead among the regulators of free-radical processes which operate by an impact on oxidative metabolism and immune response. However, the toxicity of inorganic selenium compounds - sodium selenite and selenate  - limits their widespread use in the practice of animal husbandry (1). In this regard, the most effective Se preparations are the Se-containing heterocyclic organic low-toxic compounds with high lypophility – phenyl- and pyrane- compaunds (2).
The purpose of our work was the comparative evaluation of biochemical and physiological parameters of the blood in lambs in early postnatal ontogenesis against the background of injections of different selenium compounds to ewes in yean.
Methods. The experiment was carried out in the agrofirm "Biokor C" Ltd. (Mokshanskij district, Penza region) on sheep of the Tsigajskaya breed. Using the method of pairs-analogues, three groups of 15 pregnant ewes were formed, each ewe had an average live weight of 50,0 ± 2,3 kg. All the animals were housed under identical feeding and keeping conditions.
In 14 days before lambing, the ewes were injected with preparations: sterile saline (the control group), an aqueous solution of sodium selenite at a dose of 0.1 mg selenium per 1 kg bw (the experimental group I) and the oil solution of selenopyran (9-phenyl- symmetrical oktagidroselenoksanten - SP-1) an the same dose (the experimental group II).
The biological materials for study were the blood taken from the jugular vein of lambs on the 1 st, 3 rd, 7 th, 21 st, 60 th and 90 th days after birth, and colostrum and milk of ewes, obtained on the 1 st, 3 rd, 7 th and 21 st days of lactation.
Se content in colostrum, in the blood and blood serum were determined fluorimetrically (the method modification by N.A. Golubkina using the fluorimeter Fluorat-02-2M, Russia) (3, 4), the activity of glutathione peroxidase (GPO) - by the method of G. Mills (5), superoxide dismutase (SOD) - by the method of M. Niashikimi et al. in modification of G.U. Maltsev and A.V. Vasilyeva (6), hemoglobin in the blood – by the hemoglobin-cyanide method with the test set, the total protein in blood serum was determined refractometrically.
The data were processed statistically using MS Excel software package.
Results.  The intramuscular injections of sodium selenite and SP-1 in 2 weeks before lambing caused an ambiguous impact on Se content in ewes’ colostrum, as well as in the blood and serum in their lambs (Table 1).
Se content in colostrum was highest at the beginning of lactation and was decreasing with the raise of milk secretion. During 7 days after lambing, Se content in colostrum and milk of ewes in experimental groups was higher than in control.
The decrease of Se content in colostrum in all the groups is associated with the transport of immunologically active proteins and Se in colostrum from mother to offspring.
Fast excretion of Se in ewes after lambing suggests the advisability of selenium compounds introduction to prevent Se deficit in newborn lambs.
Introduction of selenium compounds to ewes before lambing affected the raise of Se content in the blood and serum of lambs.

Se content in the blood of lambs for 7 days was correlated with Se content in colostrum (r = 0,51, r = 0,99 and r = 0,88, respectively, for the experimental groups I and II). On the 21 st day, the sharp increase of Se content in blood was observed in all groups (20.3, 22,6 and 30,4%, respectively), which is likely due to the transitional type of digestion in lambs during this period when they gradually acquire the ability to digest plant food.
From the 1 st to 7 th day after lambing, Se content in blood serum of lambs was positively correlated with total protein content in serum (r = 0,36, r = 0,28 and r = 0,74, for the experimental groups I and II, respectively), because selenium is a part of selenium-containing proteins. On the 21 st day, though, Se content in blood serum of lambs increased in the control and experimental group I, while the total protein content decreased. By this period, the diet of lambs consists of ewe milk and the vegetable food both, with the selenocysteine predominance in milk, and selenomethionine - in vegetable feed. The processes of Se-Met inclusion in tissue proteins and its reverse photolytic release are slow. At the normal selenium supply of animals, amount of Se in the labile metabolic pool (specific Se-proteins + selenite + gydrogen selenide and its derivatives) averages 35-46%. The rest of selenium in the form of selenomethionine and selenocysteine is located in tissue proteins (7). Glutathione peroxidase, selenoprotein P and the other Se-specific proteins, contain Se in the form of selenocysteine (8-10) which, apparently, stimulates the increase of Se content in blood serum of lambs in the experimental group I and in control. In group II treated with the organic form of selenium, on the contrary, the decrease of Se content was found, most likely owing to the metabolism of selenopyrane. The process of selenium release from the organic form occurs by oxidative mechanisms and is more prolonged than in the case of sodium selenite: recycling of selenopyran molecules with selenium elimination occurs gradually, which provides its embedding into the active center of glutathione peroxidase (mainly - the cellular GPO).
SP-1 and sodium selenite caused the significant impact on activity of antiradical enzyme protection - superoxide dismutase and glutathione peroxidase (Table 2).

On the 3rd day after lambing, the enzyme activity decreased in lambs of all groups. The work by M. Kolesnikov and V. Kalytka (11) shows the higher intensity of lipid peroxidation in early postnatal ontogenesis as a result of adaptation to an atmospheric air, which leads to the high content of lipids peroxidation products (LPP) in erythrocytes.
In animals treated with SP-1, the stable increase in GPO activity was manifested only on the 21 st day after lambing, which can be explained by metabolic transformations of the selenoorganic compound during this period, when selenium was releasing and stimulating GPO activity. The stimulating effect of sodium selenite was manifested in lambs on the 7 th day, which can be explained by rapid inclusion into metabolism of Se ions, in which form Se is present in inorganic compounds. The high positive correlation between GPO activity and Se content in the blood was found in lambs of the experimental groups (r = 0,61 and r = 0,71, respectively), therefore, the increase in concentration of selenium in the blood stimulates GPO activity. The organic form of selenium compound promoted medium correlation between activities of SOD and MPO (r = 0,59), and high correlation - in control and in group I (r = 0,74 and r = 0,78, respectively).
The results obtained suggest that selenopyran has antioxidant properties due to its chemical structure, and it inhibits the elevation of activity of antiradical enzyme defense, thus partially providing their functions, whereas the antioxidant effect of sodium selenite is provided by stimulation of GPO activity.
Introduction of selenium compounds to pregnant ewes affected the total protein content in serum and hemoglobin content in the blood obtained from their lambs (Table 3).

We’ve established that total protein content in blood serum of lambs of experimental groups was higher than in control throughout the experiment. The least protein content was observed on the 21 st day in animals of all groups, which is, apparently, explained by elimination of passively acquired immunologically active proteins against the background of low intensity of synthesis of the own ones.
In the group of lambs, whose mothers-ewes were treated with SP-1 in yean, hemoglobin content exceeded the control, whereas in the group treated with sodium selenite in colostrum and milk, no significant differences from control were found.
The reduce of hemoglobin in lambs by the 3 rd day after lambing was associated with the fact, that foetal hemoglobin (Hb-F) has the higher affinity for oxygen than the parent (Hb-A), as Hb-F and Hb-A are adapted to the environment in which they operate. From this period, Hb-F was being replaced with Hb-A. The reduce of hemoglobin could be also associated with the low concentration of Fe in ewe milk. It should be noted, that the organic form of selenium - SP-1 - was stimulating synthesis of hemoglobin during the first 3 weeks of experiment.
The introduction of selenium compounds to pregnant ewes stimulated the intensive growth of lambs in the first 3 months of life. Throughout the experiment, the live weight of lambs of experimental groups exceeded control: in the 7-day-old lambs, it was higher by 10,9 , or 7,8% (P <0.01) than in control, and the live weight of the 3-months-old lambs of group II was higher than in group I by 13,3% (P < 0.05), and  by 18.6% (P <0.01) higher than in control.
The positive effect of selenopyrane on live weight of lambs was most likely due to raising the level of immunological and physiological protection, rather than the direct stimulation of growth of young animals.
So, the introduction of selenium compounds (sodium selenite and selenopyran) to pregnant ewes in 2 weeks before lambing helps to optimize the ratio between the intensity of free radical oxidation and antioxidant potential in lambs, which increases their physiological and immunological status. The most pronounced effects were found from the organic form of selenium - selenopyran.

REFERENCES

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1Penza State Agricultural Academy, Penza 440014, Russia, e-mail: psaca@penza.com.ru b Scientific Research and Technological Institute of Biological Industry, Russian Agricultural Academy,  vil. Kashintsevo 141142, Moskow reg., Russia e-mail: dims82@inbox.ru

Received November 24, 2009

All-Russian Institute for Selection and Seed-Breeding of Vegetables All-Russian Selection and Technological Institute of Horticulture and Breeding Nursery Institute of Agricultural Biotechnology Joint Stock Company "GosNIISyntezBelok"