Evaluation of the Dietary Black Soldier Fly Larvae Meal (Hermetia illucens) on Growth Performance, Intestinal Health, and Disease Resistance to Vibrio parahaemolyticus of the Pacific White Shrimp (Litopenaeus vannamei)

Abstract

The present study evaluated the effects of the dietary black soldier fly larvae meal (BSF) on growth performance, intestinal health, and susceptibility to Vibrio parahaemolyticus in the Pacific white shrimp Litopenaeus vannamei. The basal diet was formulated to contain 25% fish meal (FM), and then the FM was replaced with BSF for 10, 20, and 30% of the FM protein in the experimental diets, which are referred to as FM, BSF10, BSF20, and BSF30, respectively. Four hundred and eighty healthy and uniform-sized shrimp (~0.88 g) were distributed among four groups of three replicates, each with 40 shrimp in a 300-L tank and they were fed four times daily for 7 weeks. The results showed that the growth performance did not change significantly in shrimp fed with BSF10 and BSF20 diets, but significantly decreased in those fed with BSF30 diet compared to the ones fed with FM diet. After feeding trial and sampling, a V. parahaemolyticus infection challenge trial was conducted on shrimp. The results showed that the survival rate of shrimp fed with BSF10 was significantly higher than those fed with FM. The results of the midgut histology showed that the width and height of intestinal mucosal folds decreased significantly in shrimp fed with BSF20 and BSF30, and the early signs of apoptosis in the intestinal cells were found in shrimp fed with BSF30. The mRNA levels of non-specific immune-related genes dorsal and relish were downregulated in shrimp fed with BSF20 and BSF30 diets. The mRNA levels of antimicrobial peptides–related genes alf (anti-lipopolysaccharide factor) were upregulated in shrimp fed with BSF10 but downregulated in shrimp fed with BSF30. The mRNA level pen3 (penaeidins 3) was upregulated in shrimp fed with BSF10 and BSF20 diets. The intestinal bacterial communities on operational taxonomic unit levels among groups were not significantly differentiated according to the beta diversity analysis. At the genus levels, a decrease in Vibrio, Photobacterium, and Candidatus_Bacilloplasma, as well as the increase in Bacillus and Pseudoalteromonas abundance, indicated the improvement of intestinal microbiota in shrimp fed with dietary BSF. Therefore, the use of BSF in shrimp diet should be controlled at a dosage of 20% of the FM, which can improve the intestinal microbiota without causing any negative effects.