Effects of dietary vitamin A or β-carotene concentrations on growth of juvenile hybrid tilapia, Oreochromis niloticus × O. aureus

A series of two 10-week feeding trials was conducted to evaluate the effects of dietary vitamin A or β-carotene supplementation on the growth of hybrid tilapia. In trial I, tilapia of 1.60 g body weight were fed diets supplemented with 0 to 50,000 IU vitamin A (as retinyl acetate) kg− 1. In trial II, basal diets without vitamin A supplementation were supplemented with 0 to 200 mg β-carotene/kg and fed to tilapia of 0.48 g initial weight. Growth performance of fish fed diets without vitamin A or β-carotene supplementation was significantly (P < 0.05) lower than other groups within the trial. Analyzed by the broken-line regression model, dietary vitamin A required for optimal growth of juvenile tilapia was 5850 to 6970 IU kg− 1 based on the weight gain and liver vitamin A retention. Further, dietary β-carotene for optimal growth of juvenile tilapia was 28.6 to 44.3 mg kg− 1 at a dietary vitamin A content of 84 IU kg− 1. Tilapia is able to utilize β-carotene to fulfill the dietary vitamin A requirements. The conversion ratio by weights of β-carotene to vitamin A was approximately 19 : 1.