Effects of dietary β-carotene on growth and pigmentation of ornamental carp (koi, Cyprinus carpio L.)

The study aimed at testing the effects of dietary β-carotene supplementation on growth, feed utilization and pigmentation of koi carp (Cyprinus carpio) fry (mean weight 0.43±0.00g and total length of 1.34±0.00cm). Five levels of carotenoid concentrations (0.00, 0.003, 0.006, 0.008, 0.010g/kg) were employed to formulate a 38.00% protein balanced diet. The diets were designated and referred to as Control, Diet 1, Diet 2, Diet 3 and Diet 4 respectively. Fish were stocked at 10fish/15.6litre capacity aquaria and reared for 12weeks. Fry were fed in triplicates at 5% body weight. The database was analyzed and results revealed a dose dependent percentage weight gain with koi carp treated with the extracts experiencing 667.44±10.48%, 691.47±2.79%, 865.12±16.33% and 854.34±12.42% for Diets 1 to 4 respectively. Proximate analysis of fish flesh revealed no significant differences (p<0.05) between treatments in all the parameters. Astaxanthin dominated the body of koi carp, regardless of the concentrations of dietary β-carotene included in the diets. Survival rates were generally high and was not particularly dependent on carotenoid inclusion level. Inference from the study showed that β-carotene at 0.003g/kg to 0.010g/kg inclusion in the diets resulted in increased food conversion, mean weight gain, specific growth rate and protein efficiency ratio. Keywords: β-carotene, growth, survival, feed utilization, koi carp.