Dietary inclusion of Tenebrio molitor larvae meal: effects on growth performance and final quality treats of blackspot sea bream (Pagellus bogaraveo)

This study evaluated the effects of diets containing Tenebrio molitor (TM) larvae meal in partial replacement of fishmeal (FM) on growth performances, marketable, physical and chemical traits of wild-caught blackspot sea bream, a promising finfish species for Mediterranean aquaculture. One hundred thirty fish were randomly divided into three groups with three replicates each. Fish were fed diets differing in TM inclusion percentage: 0% (TM0), 25% (TM25) and 50% (TM50) of fishmeal replacement for 131 days. Daily intake ratio, feed conversion ratio and specific growth rate were not affected by different diets, like slaughter traits and carcass yield. No significant differences were detected for some fillet quality parameters, such as water holding capacity and texture characteristics (hardness, cohesiveness, resilience, gumminess and adhesiveness), whilst pH value was found lower in TM50 than in TM0 and TM25 specimens. Different diets did not affect the colour of the skin dorsal region, unlike the skin ventral region where significant variations in colour were observed, as lightness and hue were lower while redness was higher in TM50 group than in the other two groups. Regarding colour of fillet epaxial region, yellowness and chroma were higher when TM was added in the diets; instead Hue resulted higher in fish fed diet containing FM as exclusive source of protein. In the fillet hypaxial region, the colour presented yellowness and chroma values lower in TM0 and TM25 groups than in TM50 group; whilst this last showed the lowest value for hue. Fillets proximate composition was not affected by the diet, unlike the fatty acids profile. Σn3 FA, especially EPA, was higher in fish fed TM0 diet, even if the differences were low in value. No statistical differences were found as regards DHA even if the amounts diminished when TM was added in diets. On the contrary Σn6, especially linoleic acid, significantly increased with TM inclusion in the diets. The Σn3/Σn6 FA ratio was linearly (TM0>TM25>TM50) reduced by TM inclusion in the diet and TM50 specimens had the highest (i.e. the worst) values for Atherogenicity and Thrombogenicity Indexes. Since no detrimental effects on growth performance were found, the use of Tenebrio molitor meal as alternative protein source in blackspot sea bream diet seems to be encouraging, but the effects on fillet quality should be considered.