Effects of nano selenium particles, mineral selenium and αlfa-tocopherol on glutathione peroxidase activity, blood selenium level and weight gain in suckling lambs

Selenium and α-tocopherol are considered as the main antioxidants necessary for growth of lambs (Shi et al 2010). They are responsible for reducing and eliminating body cells and their membranes from peroxides and oxidative stress (El-Shahat et al 2011). Selenium activate the body immunity and nervous system results in the prevention of diseases and low weight gain (Eekeren et al 2011). α-tocopherol eliminates peroxides from cell membrane and protects from oxidative stress (Joshi et al 2013). The administration of selenium components and α-tocopherol as orally or injection, individually or together has shown the acceptable response to growth, diseases control and treatment in lambs (Vignola et al 2007). Despite progress in resolving Se/α-tocopherol deficiency, efforts have been made to introduce new selenium compounds with high efficiency and low side effects to enhance animals’ production (Shi et al 2011). The priorities of nanoselenium are low dose administration, low toxicity and suitable effect on health and growth rate. Nanoselenium is efficient for production, reproduction performances and immunity system (Yang et al 2009). Despite a greater knowledge of NanoSe in animals, there is a lack of unity and intensive study with regard to the main relevant parameters such as age, gender, various selenium compounds with αtocopherol, route of administration and their interrelationships with weight gain in one unit study. The objectives were to find the effect of selenium components and α-tocopherol on blood GPX, selenium and their relationships with weight gain in lambs.
Thirty-two suckling male lambs were classified in 8 groups of 4 lambs including control, oral nanoselenium (ONanoSe), ONanoSe/α-tocopherol, oral sodium selenite (ONaSe), ONaSe/α-tocopherol, sodium selenite injection/α-tocopherol (INaSe/VitE), INaSe and VitE injection. Lambs were weighed and bled days 1, 4, 7, 30, 60 and 90. Recommended dose for NanoSe with no side effects is 0.10 mg kg-1 of live weight (Shi et al 2011). The amount of NanoSe and NaSe was calculated based on the weight of each lamb and was divided into seven parts, administered daily up to seven days. The dose for α-tocopherol is 8 mg kg-1 injected separately or with selenium components. Growth rate was calculated as total (Kg), percentage (%) and daily weight gain (gr/day). Blood GPX activity, blood and milk selenium concentration were measured by spectrophotometer and atomic absorption methods. Data were analyzed by ANOVA, repeated measure correlation methods.
Blood GPX activity increased 3.25-fold in lambs receiving selenium components and was consistent with the findings of Xu et al (2005) and Najafnejad et al (2016) in animals. Increase in GPX activity is an indication of organic, inorganic and nano-particles of selenium components in lambs. GPX activity in lambs receiving oral NanoSe was greater than in NaSe groups. This result is supported by Shi et al's findings (2011) which mentioned that the antioxidant and GPX activity of oral NanoSe is more effective than NaSe. Although the antioxidant effects of α-tocopherol are confirmed by scientists, in this study it had the lowest effects on GPX activity in lambs, which means that its effect on GPX was very low and weaker than selenium but together with selenium, it had suitable increase in GPX activity (Bribiesca et al 2005). This finding was not supported by Joshi et al's results (Joshi et al 2013) which mentioned that injection or oral α-tocopherol is necessary to eliminate and prevent the oxidative stress effects in animals. GPX or selenoenzyme plays an important role against oxidative stress (Huang et al 2009, Yang et al 2009). Blood selenium concentration reached to 1.48-fold at the end of study, nearly one and half times less than GPX changes in lambs receiving selenium components. Similar findings were reported by Bribiesca et al (2005) who concluded that blood selenium increased following consumption of oral or selenium injection components. An increase in blood selenium in lambs with NanoSe/αtocopherol was higher than in NaSe/α-tocopherol which is consistent with Shi et al's findings (Shi et al 2010) which referred to high selenium level in blood and tissues following NanoSe consumption. Blood selenium increased rapidly and continuously and reached to the highest level at 90 days but in Bribiescal et al's finding (2005) it was 60 days. An increase in blood selenium in lambs with NanoSe/α-tocopherol was more than other selenium components and/or with α-tocopherol, indicates that permanence and performance of new selenium compounds had priority over the old selenium (organic and inorganic) supplementation. This finding is supported by the reports of Shi et al. (2010) and Chorfi et al (2011) who concluded that NanoSe compounds increase selenium and GPX level more effectively than NaSe and the efficiency of selenium/α-tocopherol together instead of being used separately in animals. The highest daily mean weight gain was in NaSe/α-tocopherol which was greater than that reported by Vignola et al (2007) and indicates the efficiency of NaSe/αtocopherol on weight gain of lambs. The lowest weight gain observed in α-tocopherol group that was even higher than reported by Vignola et al (2007), means that α-tocopherol had an effect on growth rate. This was not in agreement with Horn et al (32) who mentioned that α-tocopherol did not have an effect on calf growth rate. Studies on the effects of selenium on growth and weight gain were controversial and mostly did not have a significant effect on weight gain. Hu et al (2007) reported significant increase in weight gain following selenium/α-tocopherol, but Mohri et al (2011) showed no effect on weight gain. No correlation was observed between lambs receiving selenium compounds and α-tocopherol with blood GPX, selenium and weight gain indices in groups except for total weight gain/GPX which was positive in oral NanoSe group. This was consistent with Yaghmaei et al’s finding (2017) reported for female lambs. However, the rate of correlation in control and α-tocopherol groups was less than selenium groups. This was in agreement with others (Juniper et al 2006, White et al 2007) that mentioned the strong positive correlation between selenium and GPX. The presence of correlation up to 98% in NanoSe lambs and less in NaSe group indicates that GPX activity in NanoSe groups was higher than NaSe groups and this can be considered one of the points to replace it with NaSe in lambs.
Se mainly ONanoSe increased GPX and Se more than α-tocopherol. Weight gain was high in ONaSe but not correlated to Se components. Correlations between Se/GPX were positive. Finally, the effect of ONanose on GPX, Se and weight gain were not higher than ONaSe mainly on increasing of GPX was better than mineral selenium and α-tocopherol, and therefore, could be the appropriate option to NaSe administration in lambs.