This study aimed to verify the potential of calcium lactate for the performance, blood index, shinbone quality, jejunal immunity, and egg quality of aged laying hens. A total of 360 62-week-old Hy-Line Brown laying hens were randomly divided into four treatments, with six replicates and 15 chickens per replicate. Experimental groups were fed with 0.25%, 0.5%, and 1.0% calcium lactate to substitute limestone in the control group (maintaining the same amount of calcium). The feeding trial lasted for 12 weeks. The laying rate and daily egg mass of laying hens fed the diets supplemented with calcium lactate was increased relative to those of the control group. The dietary addition of calcium lactate for laying hens enhanced the eggshell ratio, eggshell thickness, eggshell strength, and albumen height of eggs, and the addition level of 0.5% had the best effect. Dietary calcium lactate increased the number of red blood cells, corpuscular hemoglobin, mononuclear leucocytes and basophilic granulocytes, and decreased heterophils in the blood of laying hens. The activities of serum alanine transaminase and creatine kinase in laying hens was reduced by the dietary addition of calcium lactate. Calcium lactate supplementation in diets increased the serum calcium and phosphorus contents of laying hens. The dietary inclusion of calcium lactate increased the contents of IgA, IgG, lysozyme, and sIgA in the jejunal mucosa, and the 0.5% addition level worked best, but the IL-2 content decreased. The addition of 0.5% calcium lactate to the diet reduced the maximal force of the shinbone and increased the work required for shinbone rupture in laying hens. In conclusion, the dietary addition of calcium lactate improved the performance and egg quality of laying hens, probably by its positive effects on body health, intestinal digestible ability, calcium bioavailability, and jejunal mucosal immunity. The optimum amount of calcium lactate in the diet of laying hens is recommended to be 0.5%.
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