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

A trial was performed to study the efects of a partially defatted Hermetia illucens (L. 1758) larvae meal (HIM) to replace a fsh meal in the diet of an adult gilthead sea bream. Te fsh 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 coefcients (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 afected by the diet. Conversely, the 27.6% HI inclusion level worsened the specifc growth rate, feed conversion ratio, and protein efciency ratio. Histology showed no signifcant diferences between CTRL and HI25 groups. Conversely, in many of HI50 and HI75 fsh, anatomo-functional changes in the gut were observed. No statistical diferences were found among diets for ADC of dry matter, crude protein, ether extract, and gross energy. Te 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.