Comparative effects of inorganic and organic manganese supplementation on productive performance, egg quality, tibial characteristics, serum biochemical indices, and fecal Mn excretion of laying ducks

Abstract

This study aimed to compare the effects of inorganic and organic manganese (Mn) supplementation on productive performance, egg quality, tibial characteristics, serum biochemical indices, and Mn excretion in laying ducks. A total of 756 Longyan laying ducks (45 wk) were randomly assigned to 9 treatments, each with 6 replicates of 14 ducks. Ducks were fed a basal diet (30.6 mg Mn/kg) or that basal diet supplemented with 20, 40, 80, and 160 mg/kg Mn using inorganic (added as MnSO4·H2O) or organic (Mn-methionine; 8% Mn, 76% methionine) for 20 wks. Supplementation with inorganic Mn increased egg production and mass, and decreased FCR after 10 wk of feeding, and there were quadratic responses between them, and improved performance was observed with 40 mg/kg supplementation (P < 0.05). Supplementing with organic Mn, however, only increased egg production during wk 6–10 (P < 0.05), but FCR decreased linearly (P < 0.05, wk 16–20) with supplemental levels. Egg production and mass were higher with the addition of inorganic than organic Mn during wk 11–15 (P < 0.05). At wk 10, supplemental inorganic or organic Mn increased egg albumen height and Haugh unit, and with quadratic responses, and higher values were obtained with 40 mg/kg inorganic Mn supplementation (P < 0.05). Ducks supplemented with organic Mn had higher eggshell fracture toughness than that of ducks fed the basal diet or those containing inorganic Mn, and organic Mn linearly increased shell breaking strength at wk 10 (P < 0.05). Supplemental inorganic or organic Mn both increased mineral density and content, fresh and fat-free dry weight, length, calcium and Mn content of the tibias (P < 0.05), and mineral density, calcium and Mn content of tibias were higher in the ducks given organic than inorganic Mn (P < 0.05), and their values were higher with the supplementation of 80 mg/kg inorganic Mn and 20 mg/kg organic Mn (P < 0.05). Supplementation with Mn increased Mn excretion and with linear and quadratic effects, and excretion was lower with organic than inorganic Mn (P < 0.05). Overall, supplementation with inorganic Mn increased productive performance, but the benefits of organic Mn were less obvious. Both inorganic and organic Mn increased tibial characteristics and Mn excretion, with organic Mn being more effective or lower excretion. Taken together, it can be suggested that 40 ~80 mg/kg Mn from an inorganic source or 20 mg/kg Mn from an organic source would be appropriate when laying ducks were fed a typical corn-soybean meal diet (with 30.6 mg/kg basal Mn) during the laying period (45–64 wk of age).