Effects of different levels of selenium yeast (Sel-plex) in post- molting diet of laying hens on egg production performance, immune response and glutathione peroxidase activity

Selenium is an essential trace mineral required for normal growth and maintenance in poultry and specially contributes in glutathione peroxidase activity, an enzyme transforming the toxic hydrogen peroxide to harmless water and oxygen (Rotruck et al. 1973). Selenium may be present in inorganic or organic form in the diet and higher absorption being documented for the organic forms in poultry (Surai and Fisinin 2014). Selenium in its organic form shows higher bioavailability (75.7%) than selenium bound in the inorganic form (49.9%) (Mahan et al. 1999). Organic forms are part of proteins and include Se-Methionin and Se-Cystein. Organically bound selenium is mostly used in the form of Se-enriched yeast or other preparations. In addition to organic Selenium compounds, other sources have been tested and utilized, such as selenium-enriched algae Scenedesmus quadricauda, Se-enriched unicellular alga Chlorella (Travnicek et al. 2007) and Se-enriched yeast (Briens et al. 2013). Effects of various sources and levels of selenium in the diet on layers have been subject of a number of studies. Gjorgovska et al (2012) studied various levels of selenium yeast in layers and reported that supplementation of 460 mg/kg selenium yeast improved egg production performance comparing control birds. Similar findings have been reported by Heindl et al. (2010), who fed the layers up to 150 mg/kg selenium yeast. Attia et al. (2010) reported increase in egg weight of laying hens fed organic selenium. They reported that feed conversion ratio in laying hens fed diets containing 250 or 400 mg/kg Selplex, was lower as compared as control birds. Some researchers reported that immune response and activities of glutathione peroxidase in poultry plasma increased linearly with selenium concentration (Rama Rao et al. 2013; Singh et al. 2006). Zhang et al (2012) reported that low-selenium diet caused a decrease in the activities of total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activity in birds. Their study demonstrated that chickens fed diets deficient in selenium exhibited lesions in immune organs, decreased serum interleukin-1β, interleukin-2 content, indicating that oxidative stress inhibited the development of immune organs and finally impaired the immune function of chickens. Gajcevic et al (2009) reported increase in glutathione peroxidase activity in layer hens fed up to 400 mg/kg selenium yeast in diet. It has been documented that layer hens meet some oxidative attacks during force molting (Siegel 1980), therefore, the aim of this study was to evaluate the effect of different levels of selenium yeast on egg production performance, glutathione peroxidase activity and immune response of laying hens in post-molting phase.
Material and Eighty W-36 leghorn laying hens in post-molting phase (78 week) were assigned to 5 treatments with 4 replications and 4 birds each by employing a completely randomized design. After one week adaptation of hens to cages and diets, the hens were fed with 5 levels of selenium yeast (Sel-plex) (0, 150, 300, 450 and 600 mg/kg) for a period of 4 weeks. Sel-Plex ® is Alltech's organic form of selenium yeast and each kilogram of Sel-pex contains1000 mg selenium. All diets were isocaloric and isonitrogenous based on corn-soybean. Egg production percent, egg weight, egg mass, feed intake and feed conversion ratio of birds were recorded weekly and reported as hen day basis. Egg mass was calculated by multiplying the total number of eggs laid per hen by the average egg weight. In the end of experiment, one bird per replicate with average cage weight selected, blood samples were taken and glutathione peroxidase (GPx) activity was measured using Autoanalyzer system. Another bird per replicate with average cage weight selected, after injection of Influenza vaccine in breast muscle, two weeks later, immune response was measured based on Hemagglutination-Inhibition (HI) Test. All data were analyzed by ANOVA using the procedure described by the SAS Institute (2009). Tukey test was used to determine the significant differences between treatment means.
Results showed that using 300 and 450 mg/kg selenium yeast in post-molting diet of layers, significantly increased egg production rate as compared with control ones (P It is concluded that use of 300 mg/kg selenium yeast could improve egg production rate, glutathione peroxidase activity and immune response of laying hens in post-molting phase.