Effect of different diets on digestive enzyme activities, in vitro digestibility, and midgut gland structure in juvenile crayfish, Cherax quadricarinatus

Abstract

This study investigated the effects of food quality on digestive enzyme activities, in vitro protein digestibility and histological traits of the midgut gland in juvenile crayfish Cherax quadricarinatus. Animals of a wide weight range were fed different diets: two commercial diets with high or low lipid content (high lipid and low lipid, respectively) and were compared with a reference diet (RF) previously formulated for this species. Proteinase, lipase and amylase activities were significantly influenced by diet and weight. Specific trypsin activity was significantly higher for crayfish fed with the HL diet. Trypsin activity depended on diet and weight. Protein digestibility showed that HL was the most digestible diet and RF the least. The weight of the animals did not affect protein digestibility. Structural disorganization, hypertrophy of B-cells and presence of large vacuoles in R-cells were mainly observed in juveniles fed with HL, indicative of malnutrition. Thus, our data suggest that the HL diet would not be the most appropriate for C. quadricarinatus, while RF diet would be more convenient for culture of this species.