Digestive enzymes of postweaned greenlip abalone (Haliotis laevigata) are influenced by water temperatures and dietary protein levels

Digestive enzyme activities are known to fluctuate in abalone grown under different environmental conditions however the effects of different dietary regimes are less clear. Therefore, in a 12-week study, the effects of water temperature and dietary protein levels on digestive enzyme activity in postweaned (6-month-old) greenlip abalone (Haliotis laevigata) were investigated. The abalone were fed diets with crude protein levels that ranged from 27% to 36% and cultured at 14°C, 17°C and 20°C. Diets were formulated to be isoenergetic (12.5 MJ kg⁻¹ digestible energy) and isolipidic (3.6% crude lipid). Trypsin, α-amylase and lipase activities were measured in the gastrointestinal region. Trypsin, α-amylase and lipase activities significantly increased as water temperatures were raised. In addition, significantly higher α-amylase activities were observed as protein levels increased, potentially indicating a compensatory effect to increase carbohydrate utilisation for energy metabolism when in short supply. However, abalone fed high dietary protein levels may also utilise protein for energy metabolism. Further research investigating the dietary carbohydrate source for greenlip abalone is recommended. This study provides useful information on the digestive enzyme activity in postweaned greenlip abalone to improve diet strategies for sustainable production.

Abbreviated abstract: Post-weaned greenlip abalone digestive enzyme activity was examined after feeding four dietary protein levels at three different temperatures for a 12-week period. Enzyme activities were significantly increased with increasing water temperature. Additionally, significantly higher α-amylase activities were observed as protein levels increased.