Effects of Replacing Fishmeal by Raw or Lactobacillus acidophilus-Fermented Soybean Meal on Growth, Intestinal Digestive and Immune-Related Enzyme Activities, Morphology, and Microbiota in Turbot (Scophthalmus maximus L.)

Qinyuan Ma,Beili Zhang,Adri n J. Hern ndez,Lei Wang,Chaoqun Li,Yuan Tian

doi:10.1155/2022/2643235

Abstract

This study was performed to investigate the fermentation efficiency of Lactobacillus acidophilus and compare the effects of dietary soybean meal (SM) or L. acidophilus-fermented SM (LASM) on turbot. Two hundred and seventy juvenile turbots ( 13.50 ± 0.13 g ) were randomly divided into three treatments fed with a fishmeal-based diet (CNT) and two experimental diets with 45% fishmeal protein replaced by SM or LASM for 8 weeks. The results showed that fermentation significantly improved the essential amino acid profile, increased the lactic acid content, and reduced the antinutritional factor level in SM. Inferior growth of fish was observed in the SM group after the feeding trial, while the LASM group exhibited comparable performance to the CNT group. Activities of intestinal digestive enzymes (trypsin and diastase) and immune-related enzymes (alkaline phosphatase, acid phosphatase, and lysozyme) decreased significantly in the SM group, while no significant reduction was found in the LASM group compared to the CNT group. Dietary LASM alleviated SM-induced intestinal pathological disruption with higher villus and normal lamina propria width. Dietary LASM positively regulated the intestinal microbiota, making the overall profile more coherent with that in the CNT group. Spearman’s correlation analysis revealed that the altered intestinal microbiota was closely linked to the digestive enzyme activities. Collectively, this study indicated that L. acidophilus fermentation significantly improved the nutritional quality of SM and relieved SM-induced adverse effects on turbot, in terms of growth, intestinal digestive and immune-related enzyme activities, morphology, and microbiota.

Highlights

Achieving effective substitution of fishmeal in aquafeed is a key element in the sustainable development of aquaculture
L. acidophilus fermentation significantly decreased the level of antinutritional factors (ANFs) in soybean meal (SM), such as trypsin inhibitors (-86.04%), glycinin (-74.68%), and β-conglycinin (-52.16%)
L. acidophilus fermentation can improve the quality of SM through improving the essential amino acid (EAA) profile, increasing the lactic acid content, and decreasing the level of ANFs

Summary

Introduction

Achieving effective substitution of fishmeal in aquafeed is a key element in the sustainable development of aquaculture. The soaring price and limited resources of fishmeal have prompted researchers to accelerate the exploration of highquality alternative protein sources [1]. Among various alternative protein sources, soybean meal (SM) has been of special concern, owing to its high protein level, low cost, abundance, and stable supply [2]. Substituting fishmeal with SM at an excessive level generally impairs growth and digestive function and even triggers SM-induced enteropathy (SBMIE) in fish [5,6,7,8]. Exploring cost-effective means to reduce or eliminate the SM-induced adverse effects on fish has long been a focus of research into aquaculture

Methods

Results

Discussion

Conclusion