Enzyme and acid treatment of fish meal for incorporation into formulated microbound diets for barramundi (Lates calcarifer) larvae

This study reports on two experiments in which the use of enzyme- and acid-treated fish meal were evaluated for incorporation into formulated microbound diets for barramundi (Lates calcarifer) larvae. In the first experiment, partially hydrolysed fish meal was used to determine whether partial hydrolysis increased the dietary value of fish meal used in microbound diets fed to L. calcarifer larvae. Total length and dry weight at the end of the experiment were both higher for larvae fed diets containing untreated fish meal than those fed diets containing any level of hydrolysate. Larval survival ranged from 15.8% to 47.2% but there were no significant differences between treatments (Fig. 3; P > 0.05). Carcass pepsin levels of larvae fed diets containing untreated fish meal were significantly higher than pepsin levels of larvae fed all other diets (P < 0.05). The second experiment determined the effects of incorporating graded levels of denatured fish meal (DF) into microbound diets for L. calcarifer larvae. Acid treatment increased the digestibility of fish meal approximately twofold when compared with intact fish meal. Larvae fed diets containing 45% DF had significantly higher total length and dry weight at the end of the growth trial than those fed a diet containing only intact fish meal. Larval survival ranged from 30.2% to 58.2%, with no significant differences between treatments. Whole homogenate pepsin levels were significantly affected by the level of dietary DF inclusion with larvae fed diets containing a greater proportion of intact fish meal containing higher pepsin levels. There was a significant correlation between dietary DF inclusion level and decreasing pepsin level (r2 = 0.569, P < 0.01); however, larval pepsin level did not correlate to either dry weight or total length (Pearson correlation, P > 0.05). The results of this study are a valuable contribution to our understanding of factors influencing the utilization of ingredients in microbound diets developed for marine fish larvae and will facilitate development of more effective formulated foods for them. © 2008 Blackwell Publishing Ltd