Effects of Substituting Fish Meal with Two Types of Soybean Meal on Growth, Enzyme Activities, and Intestinal Morphology in Juvenile Rhynchocypris lagowskii

Abstract

This study evaluated the effects of substituting fish meal with common soybean meal (SBM) or extruded soybean meal (ESBM) on growth, digestion, some nonspecific immune markers, and intestinal morphology in juvenile minnow Rhynchocypris lagowskii. In trial 1, five experimental diets were formulated with SBM replacing 0% (fish meal control; SBM0), 12.5% (SBM12.5), 25.0% (SBM25), 37.5% (SBM37.5), and 50.0% (SBM50) of the fish meal. Rhynchocypris lagowskii (6.81 ± 0.19 g) were randomly stocked in 100‐L cylindrical plastic tanks and fed to satiation thrice daily for 56 d. After the feeding trial, there was no significant differences in weight gain ratio (WGR), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER), feed conversion ratio (FCR), and feed intake (FI) of the SBM0, SBM12.5, and SBM25 groups. But compared with the control group, WGR, SGR, and FI of the SBM37.5 and SBM50 groups were significantly decreased, FER and PER of the SBM50 group were significantly decreased, and FCR of the SBM50 group was significantly increased. Providing the SBM37.5 and SBM50 diets can significantly reduce the muscle protein content and protease activity of the hepatopancreas and intestine. Aspartate aminotransferase, alanine aminotransferase, lysozyme, and superoxide dismutase activities in the hepatopancreas decreased with increasing dietary SBM levels. Providing the SBM25, SBM37.5, and SBM50 diets caused atrophy, swelling, and rupture of the intestinal mucosal fold and separation of epithelial mucosa from the lamina propria. In trial 2, five experimental diets were formulated with ESBM replacing 0% (fish meal control; ESBM0), 12.5% (ESBM12.5), 25.0% (ESBM25), 37.5% (ESBM37.5), and 50.0% (ESBM50) of the fish meal. Rhynchocypris lagowskii (6.87 ± 0.02 g) were randomly stocked in 100‐L cylindrical plastic tanks and fed to satiation thrice daily for 56 d. After the feeding trial, WGR, FI, SGR, FER, PER, and muscle crude protein content of the ESBM50 group were significantly decreased compared with the control group, and FCR of the ESBM50 group was significantly increased. Meanwhile, the hepatopancreas and intestinal protease activities and the hepatopancreas superoxide dismutase, lysozyme, aspartate aminotransferase, and alanine aminotransferase activities decreased with increasing dietary ESBM levels, and the ESBM50 group was significantly different than the control group. Providing the ESBM37.5 and ESBM50 diets caused atrophy and rupture of intestinal mucosal fold and separation of epithelial mucosa from the lamina propria. These results indicated that SBM could replace 12.5% of fish meal in juvenile R. lagowskii diets, while ESBM could replace 25% of fish meal.

Effects of Dietary Lentinus edodes Fermentation Supplementation on Digestive Enzyme Activity, Antioxidant Capacity and Morphology of the Liver and Intestine in Largemouth Bass (Micropterus salmoides) Fed High Plant Protein Diets

“…While the demand for fishmeal has increased due to the global aquaculture industry's quick development, other factors such as declining fishmeal production and rising prices have forced people to look for high-yield, low-cost protein alternatives to fishmeal [3][4][5][6], and plant protein has received widespread attention as an ideal alternative to fishmeal. Certain plant proteins are more advantageous in terms of amino acid composition and nutrient content, so they are widely used in aquaculture [7][8][9]. However, numerous studies have also noted that using plant protein as the main protein might have a detrimental effect on fish development, liver function, and gastrointestinal health.…”