During the culture period, many factors cause fish stress, such as stocking density, water quality, environment, etc. Mineral supplementation is one way to help enhance immunity, reducing energy allocation to stress compensation and subsequent losses in growth and muscle development, resulting in better growth and higher production efficiency. Chromium plays an important role in carbohydrate, protein, and lipid metabolism. It is a key component of glucose tolerance factor (GTF), which helps increase insulin efficiency. Selenium plays an important role in growth, antioxidant, and reproductive functions. Selenium also acts in the conversion of thyroid hormones to their active form, a key to the control of metabolic rate. This study aimed to investigate the effects of chromium-L-methionine (CrMet) and zinc-L-selenomethionine (SeMet) in the diet of juvenile Nile tilapia on growth performance.
Juvenile Nile tilapia (Oreochromis niloticus) were acclimated for 2 weeks in a 1000-L tank and fed a commercial diet twice daily. Following the acclimation phase, fish were fed experimental diets twice daily at 3 to 4% body weight, for 4 weeks. Basal diet contained 36% crude protein and 6% crude lipid. CrMet and SeMet were added to the basal diet to create 6 treatments:
T1 No supplemental mineral
T2 0.5 ppm CrMet
T3 1.0 ppm CrMet
T4 0.3 ppm SeMet
T5 0.5 ppm CrMet + 0.3 ppm SeMet
T6 1.0 ppm CrMet + 0.3 ppm SeMet
Compared to Control, the combination of supplemental 0.5 ppm CrMet + 0.3 ppm SeMet significantly improved final body weight (FBW) and feed conversion ratio (FCR) by 11 and 14%, respectively, showing the highest potential for improved growth performance of Nile tilapia (Table 1). Selenium helps reduce stress by neutralizing excess free radicals and protecting cells from damage caused by oxidative stress. Chromium plays a key role in glucose metabolism by acting as a co- factor for insulin production and signaling pathway. Considering that most aquatic species, including farmed fish, are poor users of carbohydrates as an energy source, supplementation with Cr constitutes an interesting strategy to enhance glucose utilization, to spare dietary protein for muscle growth, increasing fillet and carcass yield. In addition, this protein sparing effect may help the aquaculture industry reduce feed costs through the utilization of less costly dietary energy sources, such as carbohydrates.