Defatted Black Soldier Fly Meal in Diet for Grow-Out Gilthead Seabream (Sparus aurata L. 1758): Effects on Growth Performance, Gill Cortisol Level, Digestive Enzyme Activities, and Intestinal Histological Structure

Abstract

A trial was performed to study the effects of a partially defatted Hermetia illucens (L. 1758) larvae meal (HIM) to replace a fish meal in the diet of an adult gilthead sea bream. The fish were fed for 120 days with diets containing HIM: 0% (CTRL), 25 (HI25), 50 (HI50), and 75% (HI75), corresponding to inclusion levels of 0, 9.2, 18.4, and 27.6%. A digestibility trial was carried out to evaluate the apparent digestibility coefficients (ADC). Growth performance, morphometric and biometric indexes, gill cortisol, status of gut mucosa, and the gut enzymes’ (alkaline proteases, lipase, and amylase) activity were evaluated. Morphometric and biometric indexes, digestibility, gill cortisol, and gut enzymes were not affected by the diet. Conversely, the 27.6% HI inclusion level worsened the specific growth rate, feed conversion ratio, and protein efficiency ratio. Histology showed no significant differences between CTRL and HI25 groups. Conversely, in many of HI50 and HI75 fish, anatomo-functional changes in the gut were observed. No statistical differences were found among diets for ADC of dry matter, crude protein, ether extract, and gross energy. The results showed that defatted HIM can be used as an alternative protein source up to 18.4% of the inclusion level without impacting the growth performance, gill cortisol, morphometric and biometric indexes, ADCs, and gut enzymes.

Physiological Response of European Sea Bass (Dicentrarchus labrax) Juveniles to an Acute Stress Challenge: The Impact of Partial and Total Dietary Fishmeal Replacement by an Insect Meal

“…To the best of the authors' knowledge, this is the first study evaluating the impact of FM substitution by an IM on the primary stress response of European seabass. In gilthead seabream (Sparus aurata), the inclusion of 27.6% of defatted HI to replace 75% of FM did not alter the gill cortisol levels after 17 weeks of a feeding trial [29]. Similarly, in rainbow trout (Oncorhynchus mykiss), 50% FM replacement by defatted HI (i.e., 15.7% dietary inclusion) also did not affect the primary stress response parameters, namely, ACTH and cortisol levels, after 18 weeks of feeding with the experimental diets [30].…”

Effects of Dietary Plant Protein Replacement with Insect and Poultry By-Product Meals on the Liver Health and Serum Metabolites of Sea Bream (Sparus aurata) and Sea Bass (Dicentrarchus labrax)

“…The differences in CHO and TAG levels observed among the H40, P40, and H10P30 dietary groups can be partially explained by higher intakes of digestible carbohydrates, due to the different starch contents in the replacement diets compared to that in the control diet. Additionally, the effects of chitin and taurine, present in insect meal, may have contributed to minor differences among fish fed the replacement diets [27,31,37,38,88], as well as differences in the amino acid compositions of proteins from insect and poultry by-product meals, could also have affected de novo lipid synthesis, contributing to increased serum lipid levels [91][92][93]. Indeed, the carbohydrate levels in the diet and lipid sources, as well as the proportion of saturated and unsaturated fatty acids, regulate glucose and lipid metabolism in sea bream and sea bass [94][95][96].…”

“…To date, many studies have examined the replacement of fish meal with poultry by-products and insect meals in various fish species [23][24][25][26]. For Gilthead sea bream, Sparus aurata, and European sea bass, Dicentrarchus labrax, the results obtained thus far have provided broad support for the utilization of both alternative protein sources as valid substitutes for fish meal to develop sustainable aquafeeds [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41].…”