عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Introduction: Selenium (Se), as an antioxidant element, is a neutralizing mineral for oxidative stress and urging apoptosis in stressed biological systems. Selenium is a necessary trace element for ruminants that participates in varied biological processes like antioxidant defense, production of thyroid hormone, and response of immune system. In recent years, researches have focused on the best supplementary sources of selenium to maximize biological performance. The studies about reproductive performance, such as that of Gabryszuk and Klewiec (2002), showed that injecting ewes with Se four weeks before breeding and again during the last four weeks of gestation caused a 32% increase in lambing percentage compared with Se-deﬁcient ewes. Furthermore, adequate Se status of the newborn lambs not only ensures prevention of nutritional myopathy, but also decreases losses in lamb productivity. Lambs from Se-supplemented ewes showed faster progression to stand and nurse compared with lambs from unsupplemented ewes and leading to an overall decrease in lamb mortality (Muñoz et al. 2009). It has been observed that selenium mineral supplements, such as sodium selenite and sodium selenate, have the same bioavailability. However, organic selenium supplements such as yeast selenium more effectively increase the concentration of selenium in blood and milk and may have a better bioavailability. However, the recently developed red elemental selenium has promising uses in the environmental protection from the pollution of the excessive selenium (Zhang et al. 2007). Zhang et al. (2007) synthesized nano red elemental selenium (nano-Se) with the size of 5 – 100 nm and observed that nano-Se had a similar bioavailability in rat and much less acute toxicity in mice compared with selenite. Recently, Wang et al. (2007) showed that nano-Se (20 – 60 nm) possesses equal efficacy in increasing the activities of GSH-Px in plasma and liver from male Kunming mice compared with selenomethionine. The periparturient period is the foremost necessary stage in farm animals about health standing and production. The objective of this study was to determine the effect of different sources of selenium on blood and serum selenium concentration of Khalkhali goats during late pregnancy, as well as the effect of these sources on the concentration of selenium in their kids up to four weeks and serum and colostrum immunoglobulin concentration (IgG) of mothers and kids (immediately after birth).
Material and methods: The experiment was conducted using 40 Khalkhali goats in a completely randomized design devided into four groups with 10 goats per each group. The goats were randomly allocated to four treatments to receive supplementations of 0 (control), 0.6 mg Se head−1 day−1 of seleno-methionine (SM), 0.6 mg Se head−1 day−1 of nano-selenium (SN), and 0.6 mg Se head−1 day−1 of sodium selenite (SS) from four weeks before the expected day of delivery. Their blood samples were taken at that time and on the kidding day. In addition, colostrums were collected in pre-cleaned polyethylene bottles from the goats as immediately as possible after kidding. Instantly after delivery, newborn kids were taken apart from their dams. The control group did not receive any supplement and received only the basal ration containing 0.1 mg Se kg-1 DM. Blood samples were collected from goats three weeks before the expected kidding. Blood samples of kids were taken from the jugular vein on the day of birth and 7 days after birth. Blood samples were centrifuged at 3000 rpm for 15 minutes to prepare the serum. The ELISA method was used to determine the concentration of IgG and selenium concentration was measured using the ICP-OES device. The weight of kids at the birth and up to four weeks, colostrum production in the first three days and milk production of goats for four weeks were recorded and analyzed.
Results and discussion: There were no significant differences in birth weight, weight of kids up to four weeks, colostrum production in the first three days, and milk production until the fourth week in goats. There was a significant difference between the groups in serum IgG concentration, colostrum IgG, and blood IgG concentration of kids (p < 0.05). No significant differences were observed between mineral selenium, nano-selenium, and control group. However, seleno-methionine had a significantly better performance than nano-selenium and sodium selenite. Serum and blood selenium concentrations were similar before kiding, but the concentration of selenium in serum and blood of supplemented goats was significantly higher than the control ones (P> 0.05). The results of this experiment showed that serum and blood selenium concentrations in nano-selenium recieved goats were significantly higher compared with other groups (p < 0.05). Serum and blood selenium concentrations of kids at birth and colostral selenium concentration in the experimental groups were significantly higher than the control group (P <0.05), except for the goats supplemented with selenium nanoparticles, which significantly decreased compared to the control goats. The serum selenium and blood levels of selenomethionine recieved group showed the highest selenium levels in comparison with other groups. Selenium blood levels increased significantly in the first week of life of the kids only in the organic supplementation treatment (P <0.05).
Conclusion: Organic selenium supplementation in late pregnancy was effective in transferring blood immunity from the goats to the kids and led to changes in serum and colostrum IgG levels of goats. The supplementation of different Se forms (sodium selenite, selenomethionine and elemental nano-Se) into pregnant goats’ diet increased Se status in the whole blood and serum compared with controls. Among Se sources, nano-selenium exhibited an excellent increasing Se status in pregnant goats. Current results showed differences in the transplacental Se transfer capacities of sodium selenite, selenium nanoparticles, and selenomethionine. When comparing these three Se sources, the results of the study clearly demonstrated that kids from goats receiving selenomethionine had higher whole-blood and serum-Se concentrations compared with kids from goats receiving sodium selenite and selenium nanoparticles. There was a failure of nano-selenium to increase newborn Se concentrations as compared with control. Seleno-methionine had higher transplacental transfer of Se and also resulted in higher Se concentrations in colostrum. Goats supplemented with seleno-methionine had greater colostral Se concentrations than goats supplemented with sodium selenite and selenium nanoparticles.