Research On Animal Production

Extended Abstract
Background: Oxidative stress is one of the major growth-limiting factors that occurs due to the excessive production of reactive oxygen species (ROS) and can lead to tissue damage in vital organs such as the liver and intestine. Due to their antibacterial and antioxidant properties, silver nanoparticles have been proposed as a novel solution for improving animal health and performance. Nanosilver toxicity is closely related to its biotransformation in biological systems, which includes surface oxidation of nanoparticles, release of silver ions, and interaction with biological macromolecules. The use of organic acids as feed additives in poultry nutrition can reduce the need for antibiotics. These effects are mainly due to the antibacterial properties and improved digestive function of these compounds. By reducing the growth of pathogenic bacteria and improving general health, the use of organic acid supplements can be a suitable alternative to antibiotics in poultry nutrition. On the other hand, silver nanoparticles coated on zeolite have high potential in various biological and environmental applications due to the combination of the unique properties of silver nanoparticles and the porous structure of zeolite. Recently, it has been proposed that silver nanoparticles could act as one of the factors inducing oxidative stress and affect the expression of oxidative genes. This research was conducted to investigate the effect of silver nanoparticles coated on zeolite and organic acid on the expression of superoxide dismutase, glutathione peroxidase, and catalase genes in the liver and intestine of broiler chickens.
Methods: A total of 450 one-day-old Cobb chicks were divided into five groups subdivided into six replicates, each with 15 chicks, and were kept for 42 days in the same rearing conditions in the form of a completely random design. Experimental diets were 1) a control or basal diet, 2) a basal diet supplemented by 1% clinoptilolite, 3) a basal diet supplemented by 1% clinoptilolite coated with 0.5% nanosilver, a 4) basal diet supplemented by 0.15% organic acid, and 5) a basal diet supplemented by 1% clinoptilolite coated with 0.5% nanosilver and 0.15% organic acid. Silver nanoparticles coated on clinoptilolite were investigated using XRF and FTIR techniques. On day 42, liver and intestine samples were obtained to examine gene expression levels of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT). For the start (1-21 days of age) and growth (22-42 days of age), diets were adjusted using UFFDA software, and nutritional requirements were prepared according to the recommendations of the Cobb 500 strain maintenance guide. Three biological replicates and three technical replicates were randomly selected on the 42^nd day of the breeding period, and samples were taken from the liver and small intestine (duodenum) to investigate the expression of SOD, GPX, and CAT genes. Data were analyzed using SAS software in a completely randomized design, and means were compared using the Tukey-Kramer test at a probability level of 0.05.
Results: In general, the data of this research on the 42^nd day indicated a decreasing effect of experimental treatments, especially nanoparticles, on the relative expression of the tested genes in the liver tissue. A decreasing effect of the experimental treatments was observed on the SOD gene expression, and no significant difference was observed between Z and OA treatments and the control treatment. Moreover, the relative expression of the GPX gene in all experimental treatments was lower than in the control treatment. OA and NSOA treatments showed a significant difference from the control treatment. NS and NSOA treatments showed a significant difference in the relative expression of the CAT gene with the control treatment (P < 0.05), with the lowest relative expression level belonging to the NS treatment. On the 42^nd day of the breeding period, silver nanoparticle treatment increased the relative expression of SOD and GPX genes in the intestinal tissue, and the zeolite treatment and organic acid had a decreasing effect on the expression of all three studied genes (P < 0.05). The relative expression level of the SOD gene in the intestinal tissue showed that all experimental treatments were significantly different from the control treatment (P < 0.05). NSOA and NS treatments showed higher expression, and lower expression occurred in Z and OA treatments than in the control treatment, and the lowest expression level belonged to the Z treatment. There was a significant difference between NS, OA, and Z treatments with the control treatment in the relative expression of the GPX gene in the intestinal tissue (P < 0.05). The NS treatment showed higher expression, and OA and Z treatments showed lower expression than the control treatment. In accordance with the relative expression of the CAT gene, Z and OA treatments showed a significant difference from the control treatment. Treatment Z presented the lowest relative expression of the CAT gene among all treatments. No significant difference was observed between NSOA and NS treatments and the control treatment.
Conclusion: The treatments containing silver nanoparticles and zeolite showed the greatest effect on the expression of SOD, GPX, and CAT genes, while the organic acid treatment decreased the relative expression of the mentioned genes. On the other hand, the genes involved in oxidative stress were more affected by experimental treatments with increasing the breeding period. The effect of silver nanoparticles on the genes of the oxidative system is highly dependent on the conditions of use. The appropriate concentration of these nanoparticles can serve as an effective strategy in strengthening the body's antioxidant system, but their improper use may have adverse effects. For the safe and effective use of these compounds, further studies are needed to determine the optimal dosage and their long-term effects.