Effects of black soldier fly pulp on growth performance, histomorphology and lipid metabolism gene expression of Micropterus salmoides

Abstract

A 62-day feeding trial was conducted to assess the effects of dietary black soldier fly pulp (BSFP) on growth performance, liver and intestine histomorphology, and liver lipid metabolism gene expression of Micropterus salmoides. Four isoproteic and isolipidic diets were formulated by adding BSFP (original substance) to the basal diet at the rate of 0% (BSFP0), 1% (BSFP1), 2% (BSFP2) and 4% (BSFP4), corresponding to inclusion of 0, 4.5, 9.0 and 18.0 g/kg DM in diets. Each diet was randomly assigned to triplicate groups of 35 fish per tank. Fish were fed twice daily to apparent satiation. Results indicated that fish fed BSFP2 had higher (p < 0.05) weight gain rate, specific growth rate and liver lipid content than BSFP0. Hepatocytes were observed to fill with lipids among treatments with different degrees of vacuolar degeneration and inflammatory cell infiltration in BSFP treated diets. Intestinal villus length was lower (p < 0.05) in BSFP2 and BSFP4 than in other diets, and villus width was lower (p < 0.05) in BSFP4 than BSFP0. Gene expression of peroxisome proliferators-activated receptors α and lipoprotein lipase were down-regulated (p < 0.05) with increased dietary BSFP levels. Acetyl-CoA carboxylase 1 was higher (p < 0.05) in fish fed BSFP4 than other diets. It was concluded that dietary inclusion of BSFP increased specific growth rate and lipid deposition, and included inflammation or damage in the liver and intestine of Micropterus salmoides.