Replacement of fish meal by black soldier fly larvae meal in diet for goldfish Carassius auratus: Growth performance, hematology, histology, total carotenoids, and coloration

Abstract

Black soldier fly (Hermetia illucens) larvae meal (BSFLM) is a promising animal feed ingredient because of its high protein content and sustainable nature in the aquaculture sector. For the potential application of this ingredient in goldfish culture, five isonitrogenous (42% of crude protein) and isolipidic (9% of crude fat) diets were prepared to replace 0, 43, 84, 145, and 210 g kg−1 fish meal (FM) with BSFLM (termed BSFLM0 – BSFLM210). Triplicate groups of 20 goldfish (approximately 9.35 ± 0.02 g fish−1) per tank were randomly assigned one of the experimental diets and fed three times daily to satiation for 10 weeks. Dietary inclusion of BSFLM linearly increased final body weight, weight gain, and specific growth rate (P < 0.001), and linearly and quadratically improved feed conversion ratio, protein efficiency ratio, and protein productive value (P < 0.05). The highest weight gain was observed in the BSFLM145 (15.61 g fish−1) group without a significant difference (P > 0.05) with BSFLM210 (14.76 g fish–1). Organosomatic indexes were similar among dietary treatments (P > 0.05). Whole-body moisture and ash contents were not significantly affected (P > 0.05), but crude protein and fat content were affected by BSFLM inclusion (P < 0.05). Regarding muscle fatty acid composition, C12:0 and C14:0 increased linearly and quadratically with BSFLM levels, resulting in an increase in total saturated fatty acids with linear and quadratic effects (P < 0.05). In contrast, C18:3n-3, C20:5n-3, C22:6n-3, total polyunsaturated fatty acids, total n-3, and n-3/n-6 ratio decreased with increasing levels of BSFLM. The color index (a* value) was linearly and quadratically decreased in the abdominal region by BSFLM inclusion, similar to the decrease in L* and a* values in the head region. Total carotenoid contents also decreased in fin, skin, and serum by BSFLM inclusions (P < 0.05). BSFLM inclusion decreased aspartate aminotransferase, alanine aminotransferase, total cholesterol, and low-density lipoprotein cholesterol with linear and quadratic effects (P < 0.05). A mild degree of vacuolization with swollen hepatocellular was observed in the BSFLM84 group, being more abundant in BSFLM145 and BSFLM210 groups. Overall, dietary BSFLM inclusion improved growth performance, feed utilization, and blood biochemistries in goldfish, but it exerted a negative effect on carotenoid content, skin coloration and liver histological integrity.