Document Type : Research Paper
Authors
1 Agricultural Research,Education and Extension Organization
2 Department of Animal and Poultry Nutrition, Gorgan University of Agricultural Sciences and Natural Resources
3 Department of Research and Development Arka Industrial Clusterm
4 Department of Animal and Poultry Genetics. Breeding and Physiology. Gorgan University of Agricultural Sciences and Natural Resources
Abstract
objective: Enhancing the nutritional quality of eggs through enrichment with micronutrients such as selenium is a value-adding strategy in the poultry industry. Selenium-enriched eggs can not only help supply this essential element in the human diet but may also lead to improved oxidative stability and longer shelf life of the product due to their enhanced antioxidant profile. Furthermore, selenium's role in regulating the expression of genes involved in oxidative stress response and detoxification pathways reveals another layer of its positive effects on cellular health. Given the inherent differences among various selenium sources in absorption, metabolism, and bioavailability, a precise evaluation of their impact on performance, health, and product quality in laying hens is essential. Therefore, this study aimed to compare the effects of dietary supplementation with two common selenium sources (sodium selenite and selenomethionine) at two different levels on production performance, oxidative stress indicators, selenium accumulation in eggs and liver, and the expression of key antioxidant genes in the liver of laying hens.
Method: An experiment was conducted using 300 Hy-Line W-36 laying hens in a completely randomized design with 5 treatments, 4 replicates, and 10 birds per replicate. The experimental treatments included: 1) Basal diet (without selenium), 2) Basal diet + 0.5 mg/kg sodium selenite, 3) Basal diet + 1 mg/kg sodium selenite, 4) Basal diet + 0.5 mg/kg selenomethionine, and 5) Basal diet + 1 mg/kg selenomethionine. Performance traits, including feed intake, body weight gain, and feed conversion ratio, were measured periodically. Antioxidant activity, expression of GPx and TXNRD1 genes, and selenium deposition in egg yolk, egg albumen, and liver were evaluated. Statistical analysis of the data was performed using SAS software.
Results: The results showed that supplementation with different organic and inorganic selenium sources had no significant effect on average weight gain, feed intake, or feed conversion ratio in laying hens during any production period (P>0.05). Similarly, plasma antioxidant activity and malondialdehyde (MDA) levels were not significantly affected by different selenium sources (P>0.05). However, selenium supplementation led to a significant decrease in hepatic MDA levels compared to the control group (P<0.05). Treatments receiving organic selenium showed significantly lower hepatic MDA production compared to those receiving inorganic selenium (P<0.05). Supplementation with 1 mg/kg organic selenium resulted in significantly higher selenium deposition in dried egg yolk and albumen compared to other experimental treatments (P<0.05). Selenium supplementation significantly increased selenium concentration in fresh egg yolk and albumen (P<0.05) and significantly elevated selenium concentration in the liver (P<0.05). Treatments receiving organic selenium showed higher expression levels of GSH and TXNRD1 genes compared to those receiving inorganic selenium (P<0.05).
Conclusions: Based on the findings, although selenium did not significantly affect performance indicators, dietary supplementation with 1 mg/kg selenomethionine reduced MDA levels, increased selenium content in eggs, and positively regulated the expression of antioxidant genes. Therefore, it can be recommended as an effective nutritional strategy to enhance bird health and improve the nutritional quality of eggs.
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