## 4 Discussion  
From a nutritional point of view, the two microalgae (chlorella and spirulina) are considered food additives with high biological value due to their nutrient concentration. The results of our study analyses strongly indicate that spirulina shows higher antioxidant properties, carotenoid levels, polyphenols, and a superior DPPH inhibition, when compared to chlorella, which suggests that spirulina has a greater capacity to combat oxidative stress. On the other hand, the microalgae proximal composition showed that chlorella had a higher concentration of PUFA, particularly omega-3 fatty acids and a higher omega-3 content, and lower \(\sum\) PUFA n-6/\(\sum\) PUFA n-3 ratio compared to spirulina. Other authors confirm that the microalgae contain the highest protein value with an excellent essential amino acid profile [33; 34], bioactive compounds, PUFA fatty acids, polysaccharides, volatile and phenolic compounds, vitamins, sterols, and natural pigments [35]. The high levels of carotenoids and fatty acids, especially \(\alpha\)-linolenic, are associated with health benefits and nutrition [36]. The microalgae utilization in animal feed improves productive performance, the immune system, antioxidant activity, and tissue regeneration [35]. Other authors [37] found a concentration of 3.291 mg/L chlorophyll \(a\), 1.174 mg/L chlorophyll \(b\), 4.466 mg/L total chlorophyll, and 0.919 mg/L carotenoids in blue-green algae spirulina. [PERSON] et al. [38] stated that chlorella possesses chloroplasts that contain green photosynthetic pigments called chlorophylls \(a\) and \(b\). Utilizing the process of photosynthesis, it exhibits rapid growth and multiplication by utilizing carbon dioxide, water, sunlight, and a minimal amount of minerals. Similar findings to our results have been reported in other studies investigating the antioxidant activity and fatty acid composition of spirulina and chlorella. [PERSON] et al. [39] found that spirulina exhibited significantly higher antioxidant activity compared to the control group. The presence of active compounds such as phycocyanin and beta-carotene in spirulina contributed to its strong antioxidant potential. In a study, [PERSON] et al. [40] stated that phycocyanin is the main antioxidant of spirulina, offering various uses for health benefits, although care should be taken in terms of the antioxidant activity, which fluctuates. Numerous studies have highlighted the higher antioxidant capacity and beneficial fatty acid profiles, including higher concentrations of omega-3 polyunsaturated fatty acids, in both microalgae species compared to control groups. These fatty acids are known for their beneficial effects on human health, including cardiovascular health and anti-inflammatory properties. Another study by [41] investigated the fatty acid profiles of microalgae species and found that both spirulina and chlorella exhibited higher concentrations of omega-3 fatty acids, particularly ALA, compared to the control group. They also noted that these microalgae species had lower levels of saturated fatty acids, contributing to a more desirable fatty acid composition. Other researchers [42] evaluated the fatty acid composition of spirulina and highlighted its high content of gamma-linolenic acid (GLA), an omega-6 fatty acid with anti-inflammatory properties. Our research revealed that adding chlorella and spirulina to the laying hens' diet at a 2% inclusion rate did not have a significant impact on initial or final body weight. Nevertheless, the group supplemented with spirulina demonstrated enhanced feed conversion efficiency, larger eggs, and higher rates of egg production compared to the control and chlorella groups. This suggests that dietary supplementation with spirulina could have more pronounced positive effects on egg production efficiency and size uniformity, with practical benefits for egg producers and consumer health.