Background:Manganese (Mn) is an important trace element for laying hen’s nutrition, which is required in small amounts in the diet. Its deficiency results in lowered production performance and eggshell quality. Objectives:This experiment was conducted to investigate the influence of different sources and levels of manganese (Mn) on egg production performance and eggshell quality in aged laying hens. Methods:A total of 720, 83-week-old Hy-Line W-36 laying hens were allocated to a completely randomized design with ten treatments; non-Mn supplemented basal diet (10.34 mg/kg Mn concentration), basal diet supplementation by three sources (Mn-oxide, Mn-sulphate, and Organic-Mn) in three graded levels (+30 mg/kg) Mn with six replicates and 12 birds each. The experimental periods included a 4-week Mn-exhaustion phase fed non-Mn supplemented basal diet, followed by a 12-week fed experimental diet. Results:Dietary supplementation with either organic or inorganic Mn sources significantly enhanced the egg production (EP), egg mass (EM) and feed conversion ratio (FCR), and relative eggshell weight (RESW) compared with the non-Mn supplemented diet. However, the experimental diets did not influence feed intake (FI), egg weight, and other eggshell quality traits. Based on the broken line regression models, the performance traits were optimized at 30-40 mg/kg Mn concentration when supplemented by Mn-sulphate or Mn-organic. Although, it was 80-90 mg/kg when supplemented by Mn-oxide. The relative bio-efficacy (RBE) of inorganic Mn source include Mn-oxide and Mn-sulphate were estimated 45 & 87% (EP), 30 & 94% (EM), 36 & 99% (FCR), and 37 & 78% (RESW) as efficacious as Mn-organic at equimolar Mn levels. Conclusions:In the aged laying hens, Mn requirement is higher than the NRC (1994) recommendation. Sulphate and organic sources of manganese are more effective than Mn-oxide. https://doi.org/10.1002/vms3.1116

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