Use of essential trace elements in the early life stages of barramundi Lates calcarifer: Effects on the growth performance and homogeneity of fish
Barramundi (Lates calcarifer, L.) is a predatory fish species native in Southeast Asia. Based on the geothermal potentiality of Hungary the high market potential warm-water fish barramundi can be produced economically. Essential trace elements play an important role in fish nutrition. Cobalt, manganese and zinc are vital in trace amount for many living functions of vertebrates. The advantageous effects of manganese and zinc on the vertebral development and optimal fish growth are already reported, however, lower number of papers is available regarding cobalt. Cobalt is necessary for the synthesis of vitamin B12 and it is also a cofactor for several enzymes. Improved growth performance was observed in cases of some fish species when diet was supplemented with CoCl2.
The main aim of the current study is to investigate the effects of cobalt, manganese and zinc on the growth performance and homogeneity of fish when trace elements applied individually and in combined treatments in the early life stages of barramundi. A total of 9 treatments were set in a randomized blocked design where the concentrations of the applied elements were 50 and 100 mg L-1 for CoCl2 and for MnCl2 individually, as well as for CoCl2 along with ZnSO4 and for CoCl2 along with MnCl2 in combination. In our study, larval barramundi (15-30 day-post hatch) were fed with trace element supplemented Artemia nauplii after a 24 hours enrichment period, as well as juvenile fish (BW: 5.41±0.06 g) were fed with cobalt, manganese and zinc supplemented dry diet in an 8 weeks experiment.
Significantly improved growth (body weight and standard length) of the larvae were observed in all experimental groups compared to the control (p<0.05), while the lower concentration of individual Co supplementation resulted in the highest growth performance. However, the use of cobalt and manganese in combined treatments produced a less uniform larvae in size and as a consequence of increased heterogeneity, survival was significantly reduced by the cannibalism (p<0.05). Although the production parameters of larval barramundi were positively affected by the addition of trace elements when the retention of minerals occurred through nourishment living organisms, statistically no differences were found between the treatments considering the growing performance and size distribution of barramundi juveniles either when dry feed was supplemented with cobalt, manganese or zinc (p>0.05).
This research was realized in the frames of TÁMOP 4.2.4. A/2-11-1-2012-0001 „National Excellence Program - Elaborating and operating an inland student and researcher personal support system". The project was subsidized by the European Union and co-financed by the European Social Fund.