Dietary vitamin D3 requirement of Wuchang bream (Megalobrama amblycephala)

A 90-day feeding trial was conducted to quantify the dietary vitamin D3 requirement of Wuchang bream (Megalobrama amblycephala). Six isonitrogenous (34.39 ± 0.12%, DM) and isolipidic (6.07 ± 0.06%, DM) semi-purified diets were formulated to contain graded vitamin D3 levels (0, 0.50, 1.00, 2.00, 4.00, and 8.00 IU/g diet). At the end of the feeding trial, the growth performance, body and muscle composition, plasma and body physiological and biochemical index, including calcium, phosphorus, cholesterol, triglycerides, glucose and insulin, were determined. Based on the SGR and FCR, the optimal dietary vitamin D3 requirement of Wuchang bream was estimated to be 5.43 IU/g and 4.97 IU/g using broken line regression estimation method, respectively. Whole body composition was independent of dietary vitamin D3 levels, except for crude lipid, while muscle crude protein, crude lipid and ash were significantly dependent on dietary vitamin D3 levels. The phosphorus content in plasma, whole body and muscle were independent of dietary vitamin D3 levels. The calcium content in plasma increased with increasing dietary vitamin D3 level from diet 0 to 1 IU/g, and thereafter declined with 2, 4 and 8 diets. Significantly higher plasma cholesterol, triglycerides and insulin content were observed in fish fed diets containing 8 and 2 IU/g vitamin D3 (P < 0.05), while no significant differences in glucose content were observed with different dietary vitamin D3 levels (P > 0.05).