THE EFFECT OF PYRIDOXINE SUPPLEMENTATION ON DIETARY-PROTEIN UTILIZATION IN GILTHEAD SEABREAM FRY

A study was undertaken to ascertain the effect of pyridoxine in diets of varying protein to energy ratio (P:E) for Mediterranean gilthead se abream fry (Sparus aurata) with respect to protein utilization. Diets were formulated to provide three levels of added pyridoxine (0.5, 5.0 and 50.0 mg/kg), at two protein levels (320 or 470 g/kg) whilst mainta ining a similar guess isocalorific profile at 20 MJ/kg. Feeding level was proportionately 0.02 of the fish body weight per day, resulting in the following effects after a 70-day feeding trial. Low P:E ratio die ts (15 g/MJ) did not perform as well as high P:E diets (24 g/MJ), with respect to growth related indices. Higher inclusions of pyridoxine in to diets of equal P:E ratios, caused elevations in food conversion eff iciency, protein efficiency ratio and apparent net protein utilization . A marked improvement of growth rate concomitant with pyridoxine leve l only occurred in the high P:E diets. If was concluded that increment al additions of pyridoxine in the diet, increased the efficiency of pr otein utilization for all diets tested. However, the protein sparing e ffect of lipid teas not achieved for the low protein diets indicating the relatively high requirement for protein in the growth of the juven ile seabream.