Fermented Soybean Meal May Support Fish Gut Health, Fishmeal Replacement
Researchers say fermented soybean meal may increase digestibility, antioxidant capacity and immune response when alternative proteins replace fish meal in farmed Japanese salmon diets.
International research teams from China and the United States explored the use of bacterial or yeast-fermented soybean meal (SM) as a protein substitute in the diet of Japanese sea bream.
The researchers published their findings in the Journal of Fish and Shellfish Immunology.
"In this study, Bacillus sp. SE5 (BP) and Pseudozyma aphidis ZR1 (PA) isolated from the gut microbiota of Epinephelus coioides and Lithobates catesbeiana, respectively, were used to ferment SM," The researchers said.
"Then, the effect of using SM, BP fermentation SM (BPFSM) and PA fermentation SM (PAFSM) instead of 40 or 80% FM was studied to study its growth, feed utilization, blood biochemistry, innate immunity, digestive enzyme activity, intestinal tract. Expression of morphological and immune-related genes in the Japanese sea otter (Lateolabrax japonicus)," they added.
The researchers found that fish fed high-soybean meal or high Pseudozyma aphidis (PA) fermented SM diets had higher feed conversion rates and lower protein digestibility than the control group, while fish with high SM diets were generally higher. There has been a decline. Antioxidant capacity.
However, fish in the PAFSM diet had higher lysozyme activity than those receiving the SM diet, and the total antioxidant capacity (T-AOC) produced by the fish against Bacillus thuringiensis fermentation SM (BPFSM80) and PAFSM80 was compared with the control fish. Similar, they said.
"The results of this study suggest that the use of FSM sources, especially BPFSM, can increase nutrient availability, antioxidant activity and non-specific immune responses, and reduce the devastating effects of SM on intestinal health," they said. “A future supplemental study is needed to determine the optimal level of replacement for FM using two FSM sources.”
Interest in fishmeal substitutes
Fishmeal (FM) is a frequently used feed ingredient that adds protein to aquafeeds, the researchers said.
However, the use of fishmeal is considered a limiting factor in the expansion of the aquaculture industry, as prices of such components continue to rise and supply remains limited.
They say that starting from the aquatic plant industry, it is of interest to develop cheaper, more sustainable protein components from plant or animal sources.
However, alternative proteins need to be able to replace FM while supporting growth performance.
They say that multiple ingredients have been studied as potential replacements. Plant proteins have always been of interest to researchers because they tend to be cheaper and available in large quantities.
"In the plant proteins studied so far, soybean meal (SM) shows promise due to its stable supply, low price, competitive nutrients and relatively high digestibility," the researchers said. “Despite this, despite the high nutritional value, the high content of SM in the diet of carnivorous fish, coupled with adverse effects on growth, metabolism and health, has some disadvantages, such as the lack of certain essential amino acids, poor palatability and opposition. The occurrence of - Nutritional Factors (ANFs)."
They say that soy-based proteins are also associated with inhibition of immune function in several fish species. It is necessary to reduce or turn off ANF before using higher levels of soybean meal for aquafeed.
Why ferment soybean meal?
Researchers say multiple processes have been explored to improve the use of SM in fish feed. These include soaking, germination, malting, thermal or mechanical processing and fermentation.
“Fermentation has been recognized as the most cost-effective means, not only through ANFs (eg trypsin inhibitors, oligosaccharides and phytic acid), biodegradation of proteins and fibers, but also through the production of possible probiotics and prebiotics. The nutritional quality of SM. Subsequently improved palatability, nutrient digestibility and immune function," they said.
In addition, they say that the fermentation process enhances the protein content of SM and appears to increase antibacterial and antioxidant activity while limiting the immunoreactivity of immunoglobulin E.
However, since several microorganisms have been used to ferment SM, it has been found that the nutritional properties of fermented SM (FSM) vary depending on the microorganism used, they said.
They added that micro-organisms produced by fish "actuate cellulolytic and amylolytic activities, reducing crude fiber, cellulose, hemicellulose and ANF content in plant proteins."
Feeding trial overview
In the feeding trial, the fish received one of seven diets replaced with fishmeal or fishmeal, replacing the different levels of eight days with soybean meal (SM), aphid fermented soybean meal (PAFSM) or Bacillus fermented soybean meal (BPFSM). The researchers said.
“Use FM (FM diet) to prepare a basal diet and replace the 40% or 80% FM with SM, BPFSM or PAFSM (SM40, SM80, BPFSM40, BPFSM80, PAFSM40 and PAFSM80 diets) to produce the other six diets,” All diets include salmon visceral paste, which contains 42% crude protein and 10% lipid.
They said that the fish were adapted to the laboratory setting for 2 weeks before the start of the feeding trial. The fish were weighed and the growth parameters were calculated at the end of the experiment.
The researchers said that the survival rate was recorded and blood samples were taken at the end of the trial and the gut of the selected fish was analyzed. Spleen samples were taken from selected fish to examine immune-related gene expression - including lysozyme and complement C3. Check the whole body composition of the other fish.
The researchers said that feed intake and survival rates were similar for all diets, while control fish and 40% replacement diets had similar growth performance.
However, as the FM substitution of all three test proteins increased to 80%, growth performance decreased - although fish on BPFSM and PAFSM grew better than fish on the SM diet.
Fish eating SM80 and PAFSM80 diets had higher feed conversion ratio (FCR) and lower protein (ADC) apparent digestibility coefficients than the control group.
Fish that obtained the SM80 diet also showed reduced dry matter ADC and lower systemic lipid content, but higher systemic water content than controls.
They said that fermentation of SM increased the protein content of BPFSM from 50.6% to 58.5%, and the protein content of PAFSM increased by 58.4%. This process also reduces glycine content and beta-conglycinin.
They said that diet did not change serum total protein, glucose and triglyceride levels, but serum total cholesterol levels decreased in most trial diets.
They added: "In fish fed SM80, serum T-AOC decreased significantly, while the FSM-fed group showed values comparable to the FM group."
"BPFSM40-fed fish showed comparable catalase CAT activity to the FM group, while other groups showed significantly reduced activity." "Improve serum MDA concentrations by increasing FM replacement levels... in the SM80 group," the researchers said. A lower serum lysozyme activity was found, and no significant differences were found in the FM group and the FSM-fed group."
They said that the minimum activity to supplement C3 comes from fish in the SM80 diet, with fish receiving the highest proportion of BPFSM40 diet. Fish had similar lysozyme expression except for the SM80 diet, and C3 expression was comparable to that of fish in the FM, BPFSM40 and PAFSM40 diets.
They said that fish in the PAFSM diet had similar foregut lipase activity as the control, while all SM diets had fewer proteases and only SM40 fish had similar amylase activity. In the midgut, SM use only changes lipase activity.