The effects of including Hermetia illucens (HI) meal in rainbow trout diets have been widely characterized, but data related to its utilization in low-fishmeal (FM) diets are quite scarce. The current research investigated the impact of HI meal inclusion in low-FM diets for rainbow trout by assessing fish growth performance, nutrient digestibility, histomorphological traits of intestine and main organs, and gut microbiota. In the 133-days growth trial, 600 rainbow trout were randomly distributed to 4 dietary treatments (3 replicate tanks/treatment, 50 fish/tank): a low-FM diet as control (HI0), and three experimental diets including 80, 160 and 320 g/kg of HI meal as fed as replacement of 25%, 50% and 100% of FM (HI25, HI50 and HI100, respectively). At the end of the trial, growth parameters, condition factor and somatic indices were assessed, and gut, stomach, liver and spleen samples (12 fish/diet) were collected for histomorphological analyses. Feed and posterior intestine content were also sampled to characterize their microbiota. In the digestibility trial, 216 fish (3 tanks/treatment, 18 fish/tank) allowed evaluating the apparent digestibility coefficients (ADC) of the dietary nutrients. Unaffected growth performance, condition factor, somatic indices, nutrient digestibility, and histomorphological features were observed in the HI-fed rainbow trout (P > 0.05). Increasing percentages of HI meal in the feeds determined a progressive increase in the relative abundance of Firmicutes and Actinobacteria phyla, and Staphylococcus, Enterococcus, Oceanobacillus and Actinomyces genera, whereas Proteobacteria – as well as Lactobacillus and Listeria – displayed a gradual reduction. The Chao1 index of the fish gut microbiota increased when including HI meal, while the Shannon index displayed the opposite trend (P < 0.05). The HI25 and HI50 fish showed enrichment of Actinobacteria, but a reduction in Bacteroidetes (False Discovery Rate [FDR] < 0.05). Furthermore, Bacillus, Actinomyces, Staphylococcus, Enterococcus, and Oceanobacillus displayed higher relative abundance in the HI-fed fish than the other groups (FDR < 0.05). On the contrary, HI meal utilization was accompanied by a decrease in Campylobacter and Listeria, as well as Lactobacillus, Clostridium, Pediococcus, Leuconostoc, unclassified members (U.m.) of Peptostreptococceae, Vagococcus, Lactococcus, and Weissella (FDR < 0.05). In conclusion, HI meal can be used in low-FM diets for rainbow trout up to high inclusion levels (32%) without negatively affecting the fish nutrient digestibility, growth performance, somatic indices and histomorphological features. A positive shift of the gut microbiota towards the selection of short-chain fatty acids (SCFAs)-producing bacteria and reduction of foodborne disease-causing pathogens was also observed.

Hermetia illucens meal inclusion in low-fishmeal diets for rainbow trout (Oncorhynchus mykiss): Effects on the growth performance, nutrient digestibility coefficients, selected gut health traits, and health status indices

Biasato, I.;Chemello, G.;Bellezza Oddon, S.;Ferrocino, I.;Corvaglia, M. R.;Caimi, C.;Resconi, A.;Capucchio, M. T.;Colombino, E.;Cocolin, L.;Schiavone, A.;Gasco, L.
2022-01-01

Abstract

The effects of including Hermetia illucens (HI) meal in rainbow trout diets have been widely characterized, but data related to its utilization in low-fishmeal (FM) diets are quite scarce. The current research investigated the impact of HI meal inclusion in low-FM diets for rainbow trout by assessing fish growth performance, nutrient digestibility, histomorphological traits of intestine and main organs, and gut microbiota. In the 133-days growth trial, 600 rainbow trout were randomly distributed to 4 dietary treatments (3 replicate tanks/treatment, 50 fish/tank): a low-FM diet as control (HI0), and three experimental diets including 80, 160 and 320 g/kg of HI meal as fed as replacement of 25%, 50% and 100% of FM (HI25, HI50 and HI100, respectively). At the end of the trial, growth parameters, condition factor and somatic indices were assessed, and gut, stomach, liver and spleen samples (12 fish/diet) were collected for histomorphological analyses. Feed and posterior intestine content were also sampled to characterize their microbiota. In the digestibility trial, 216 fish (3 tanks/treatment, 18 fish/tank) allowed evaluating the apparent digestibility coefficients (ADC) of the dietary nutrients. Unaffected growth performance, condition factor, somatic indices, nutrient digestibility, and histomorphological features were observed in the HI-fed rainbow trout (P > 0.05). Increasing percentages of HI meal in the feeds determined a progressive increase in the relative abundance of Firmicutes and Actinobacteria phyla, and Staphylococcus, Enterococcus, Oceanobacillus and Actinomyces genera, whereas Proteobacteria – as well as Lactobacillus and Listeria – displayed a gradual reduction. The Chao1 index of the fish gut microbiota increased when including HI meal, while the Shannon index displayed the opposite trend (P < 0.05). The HI25 and HI50 fish showed enrichment of Actinobacteria, but a reduction in Bacteroidetes (False Discovery Rate [FDR] < 0.05). Furthermore, Bacillus, Actinomyces, Staphylococcus, Enterococcus, and Oceanobacillus displayed higher relative abundance in the HI-fed fish than the other groups (FDR < 0.05). On the contrary, HI meal utilization was accompanied by a decrease in Campylobacter and Listeria, as well as Lactobacillus, Clostridium, Pediococcus, Leuconostoc, unclassified members (U.m.) of Peptostreptococceae, Vagococcus, Lactococcus, and Weissella (FDR < 0.05). In conclusion, HI meal can be used in low-FM diets for rainbow trout up to high inclusion levels (32%) without negatively affecting the fish nutrient digestibility, growth performance, somatic indices and histomorphological features. A positive shift of the gut microbiota towards the selection of short-chain fatty acids (SCFAs)-producing bacteria and reduction of foodborne disease-causing pathogens was also observed.
2022
290
115341
115357
Black soldier fly; Fish; Growth performance; Gut microbiota; Insect meal; Low-fishmeal feed; Nutrient digestibility;
Biasato, I.; Chemello, G.; Bellezza Oddon, S.; Ferrocino, I.; Corvaglia, M.R.; Caimi, C.; Resconi, A.; Paul, A.; van Spankeren, M.; Capucchio, M.T.; C...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1863881
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