Digestive enzimatic activity on Piaractus mesopotamicus larvae during early life stage and under differents rearing protocols
The knowledge about organogenesis of fish larvae is a useful tool to establish their functional capabilities and systemic physiological needs in order to ensure welfare and optimal growth under aquaculture conditions. Feeding in hatchery affects digestive functions inducing faster or slower development. This study assessed the digestive capacity during the initial development of pacu and the effects of feeding and weaning on several digestive enzyme activities.
The activities of trypsin, amylase, lipase, acid proteases, leucine-aminopeptidase and maltase were evaluated throughout the larvae development from hatching to 46 days post-hatching (dph) and compared between the following dietary treatments: early weaning of artemia nauplii for commercial microdiet initiated at 16 dph; late weaning of artemia nauplii for commercial microdiet initiated at 22 dph; larvae fed exclusively artemia nauplii; and fasting larvae. Our results show enzyme activity for trypsin, lipase, amylase and leucine-aminopeptidase in larvae at 4 dah, just before the onset of exogenous feeding. Between the onset of exogenous feeding and 16 dph, amylase and trypsin specific activity increased around 3 and 7 times, respectively. Lipase and leucine-aminopeptidase specific activity showed variations and acid proteases activity became significant at 16 dpe. The pancreatic enzymes and leucine-aminopeptidase activity was influenced by weaning at least once during the weaning phase (16-46 dph).
In conclusion, pacu larvae present digestive capacity before the beginning of the exogenous feeding and, at that time, digestion relies mainly on pancreatic enzymes. After the 16th dph (~11 mg), pacu larvae can efficiently digest compound diets as they develop a functional stomach with acid protease activity and high trypsin and amylase activity compared to previous stages. Our results may be used to propose new ingredients and diets compatible with the digestive capacity of pacu larvae, and thus, begin weaning even before the larvae present functional stomach.