Effects of Low-Level Organic Acid Chelating Fe, Cu, Zn, and Mn Supplementation on Performance, Internal Egg Quality, Antioxidant Capacity, and Blood Parameters in Aged Laying Hens

The present study evaluated the effects of organic trace mineral supplementation on eggshell quality, anti-oxidant activity, immune function, blood biochemical parameters, and egg mineral composition in aged laying hens. A total of 625 Lohmann LSL-Lite laying hens were assigned randomly into five dietary treat-ment groups, each comprising five replicates of 25 hens. The experimental diets consisted of a basal formu-lation supplemented with either standard inorganic trace minerals (Fe: 75.35 mg/kg; Cu: 11.65 mg/kg; Zn: 78.8 mg/kg; Mn: 114.4 mg/kg) or varying proportions (30%, 40%, 50%, and 60%) of organic trace minerals that replace inorganic sources. The results revealed that substituting 60% of inorganic trace minerals with organic sources significantly enhanced eggshell integrity and improved performance metrics, including egg weight, egg production rate, egg mass, feed consumption, and the feed conversion ratio. Additionally, re-placing 60% of inorganic minerals with organic minerals resulted in increased deposition of iron and man-ganese in egg yolks. Furthermore, this substitution positively influenced egg composition, increasing the albumen percentage while concurrently reducing the yolk percentage. Blood biochemical analyses revealed significant reductions in cholesterol and triglyceride levels, accompanied by increased activities of antioxi-dant enzymes, specifically superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), at 50% and 60% organic mineral supplementation. However, no significant changes in serum catalase (CAT) activity or malondialdehyde (MDA) concentrations were detected across the treatment groups. In summary, partial dietary replacement of inorganic trace minerals with organic alternatives effectively improved eggshell quality, enhanced antioxidant status, and optimized biochemical parameters in older laying hens. These findings underscore the potential benefits of organic trace mineral supplementation in sustaining productiv-ity and promoting health during the later stages of the laying cycle.