Bioavailability of amino acid-chelated and glass-embedded manganese to rainbow trout, <i>Oncorhynchus mykiss</i> (Walbaum), fingerlings

Abstract

Feeding experiments were conducted to determine the bioavailability of new types of manganese (Mn) supplement to rainbow trout fingerlings. Two levels of Mn (7 and 14 mg kg−1 diet) were supplemented to diets using either manganese sulphate (Mn-S), glass-embedded Mn (Mn-Gl), or amino acid-chelated Mn (Mn-Am); more than one acid was used to chelate the metal. Rainbow trout weighing 1.30 g on average were fed the experimental diets for 12 weeks. Absorption of Mn from various compounds was evaluated using larger fish (105 g on average) fed the experimental diets. Growth was higher in the group supplemented with Mn-Am at both levels. Whole-body Mn content in fish fed the diet supplemented with Mn-Am was significantly higher than the other sources. Bone Mn accumulation was significantly higher in treatments with 14 mg Mn kg−1 diet from all sources, except Mn-Gl. At 7 mg kg−1, absorption from Mn-Am was significantly higher than from Mn-Gl and Mn-S. Mn retention from both levels of Mn-Am supplementation was significantly higher (P < 0.05) than the rest. The results indicated that amino acid-chelated Mn provided more bioavailable nutrient than Mn-S and Mn-Gl. Further, availability of Mn from Mn-Gl is equivalent to that of Mn-S.