Efficacy of inorganic and chelated trace minerals (Cu, Zn and Mn) premix sources in Pacific white shrimp, Litopenaeus vannamei (Boone) fed plant protein based diets

The present experiment was conducted to evaluate the efficacy of trace minerals (Cu, Zn and Mn) premixes from inorganic and chelated (chelated to 2-hydroxy-4-methylthiobutanoic acid or hydroxy analog of methionine; Mintrex™) sources, in juvenile Pacific white shrimp, (Litopenaeus vannamei) fed plant protein based practical diets. Eight experimental diets comprising a trace minerals (Cu, Zn and Mn) deficient Basal control, and diets supplemented with the trace mineral premixes at four different levels of 2.5 (M2.5), 5 (M5), 7.5 (M7.5) and 8.5g/kg (M8.5) from chelated source and at three different levels of 5 (I5), 8.5 (I8.5) and 20g/kg (I20) from inorganic source were formulated. Eleven numbers of juvenile shrimp averaging 0.6±0.01g (mean±SD) were fed one of the eight experimental diets in triplicate groups for 8weeks. At the end of the feeding trial, shrimp fed M2.5 and I8.5 diets exhibited the similar final weight (FW) and weight gain (WG) (P<0.05). Performance for Cu and Zn content in the hepatopancreas tissues and whole body showed equal efficiency of M5 compared to I8.5 diet (P<0.05). Whereas, nonspecific enzyme, CuZn super oxide dismutase (CuZn SOD) from the serum and hepatopancreas tissue was recorded to be peaked for the group of shrimp fed M5 diet. Moreover, plasma protein and glucose levels were recorded to be similar between the groups of shrimp fed M2.5 and I20 diets (P<0.05). Therefore, the present experiment demonstrated, a higher efficiency of chelated over inorganic source of trace mineral premix in Pacific white shrimp, (L. vannamei) fed plant protein based diets.The significance of trace mineral bioavailability has become more important as the composition of majority of commercial fish feed has been changing and there is an increased use of dietary plant protein. As a result, the bioavailability of trace minerals is being adversely affected by the presence of antagonistic factor such as phytic acid in plant protein. Even though, our knowledge in fish nutrition has advanced significantly, the information on trace minerals requirement is still limited and fragmentary. Inorganic form (sulfate/nitrate) of trace mineral has traditionally been used in aquafeed formulation. However, the limited bioavailability of inorganic source of trace mineral due to its higher affinity to antinutrients has hastened the search for alternative form of inorganic trace minerals. Overall performance observed in the present experiments vouched the potential benefit of using chelated trace mineral, Cu, Zn & Mn premix in marine shrimp, Pacific white shrimp to promote the optimum growth, trace minerals saturation in shrimp body and tissue as well as to ensure the optimum enzyme activity and health of cultured shrimp. The present experiment opens a new avenue to compare the efficacy of inorganic and chelated source of trace minerals in other commercially important marine and fresh water fish species.Whereas, the sustainability issue has put a new dimension in aquafeed formulation with a wide array of new ingredients and additives, on the other hand, the importance of basic nutrient such as trace minerals is still in sideline. Substantial investment and integrated scientific efforts are warranted to bridge the knowledge gap and further improve our understandings on the significance of dietary trace mineral in fish nutrition and health at the least cost to environment.