The Effect of Hydrolyzed Insect Meals in Sea Trout Fingerling (Salmo trutta m. trutta) Diets on Growth Performance, Microbiota and Biochemical Blood Parameters.

Zuzanna Mikołajczak,Jan Mazurkiewicz,Damian Józefiak,Mateusz Rawski,Bartosz Kierończyk

doi:10.3390/ani10061031

Zuzanna Mikołajczak, Jan Mazurkiewicz + Show 3 more

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https://doi.org/10.3390/ani10061031

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Abstract

Simple SummaryThe replacement of fishmeal by environmentally sustainable alternative meals has been one of the targets in aquaculture in recent decades. A number of factors support the use of insect meals, as a group of products characterized by high crude protein and crude fat content, in fish nutrition. Insects are readily accepted by a number of fish species, and they are part of the natural diet of omnivorous and carnivorous species. The present study was conducted to evaluate the effects of hydrolyzed Tenebrio molitor and Zophobas morio meals as a partial replacement for fishmeal in sea trout (Salmo trutta m. trutta) diets on growth performance, feed utilization, organosomatic indices, serum biochemistry, gut histology, and microbiota. In the present study, insect meals inclusion did not cause any adverse impacts on growth performance, feed utilization or gut histomorphology. However, an effect on the organosomatic indices, serum biochemistry, and microbiota was observed. In conclusion, hydrolyzed T. molitor and Z. morio meals seem to be promising alternative protein sources for sea trout nutrition.The present study is the first introduction of hydrolyzed superworm meal in sea trout nutrition. It was conducted to evaluate the effects of inclusion in the diet of hydrolyzed insect meals as a partial replacement for fishmeal on growth performance, feed utilization, organosomatic indices, serum biochemical parameters, gut histomorphology, and microbiota composition of sea trout (Salmo trutta m. trutta). The experiment was performed on 225 sea trout fingerlings distributed into three groups (3 tanks/treatment, 25 fish/tank). The control diet was fishmeal-based. In the experimental groups, 10% of hydrolyzed mealworm (TMD) and superworm (ZMD) meals were included. The protein efficiency ratio was lower in the TMD and ZMD. Higher organosomatic indices and liver lipid contents were found in the group fed ZMD. The ZMD increased levels of aspartate aminotransferase, and decreased levels of alkaline phosphatase. The Aeromonas spp. and Enterococcus spp. populations decreased in the ZMD. The concentrations of the Carnobacterium spp. decreased in the ZMD and TMD, as did that of the Lactobacillus group in the TMD. In conclusion, insect meals may be an alternative protein source in sea trout nutrition, as they yield satisfying growth performance and have the capability to modulate biochemical blood parameters and microbiota composition.

Highlights

The replacement of fishmeal (FM) by environmentally sustainable alternative protein sources has been one of the targets of aquaculture in recent decades [1]
This is caused by their high nutritive value—protein and fat content, anti-pathogenic and anti-inflammatory properties connected with antimicrobial peptides, and lauric acid and chitin presence—as well as their environmental sustainability due to their taking part in a circular economy and wide presence in the natural diets of many fish species [5,6]
Considering all the aspects mentioned above, this research aimed to evaluate the impact of mealworm (Tenebrio molitor) and superworm (Zophobas morio) larval meals hydrolyzed by bacterial enzymes and used as partial replacements for fishmeal on the blood immune responses and the microbiota of the gastrointestinal tract of sea trout compared to their growth performance and the feed efficiency

Summary

Introduction

The replacement of fishmeal (FM) by environmentally sustainable alternative protein sources has been one of the targets of aquaculture in recent decades [1]. Many alternatives can lead to secondary, adverse health effects—nutritional disorders and metabolic disturbances may be caused by the use of dietary plant meal, i.e., enteritis in the distal intestine, hypertrophic mucus production, a reduction in reproductive rates, high mortality or growth depression [14,15] Another important source of protein—animal byproducts, such as blood meal, meat and bone meal, as well as feather meal—is associated with legislative issues and consumer intolerance; it may contain antinutritional factors, i.e., indigestible pepsin or high levels of crude ash [16] or cause amino acid imbalance in the diet due to high levels of proline or glycine and low tryptophan and tyrosine content [17]

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