Abstract: [Objective]To investigate the impact of substituting wet fermented soybean meal for soybean meal on the growth performance, serum immune parameters, intestinal permeability, and muscle fatty acid composition of broilers, thereby providing a scientific basis for the utilization of wet fermented soybean meal in broiler production. [Method]A total of 320 1-day-old AA broilers were randomly allocated into control and experimental groups. Each group consisted of 8 replicates, pre-group with each replicate comprising 20 chicks. The control group was fed a basic diet, while the experimental group received a diet in which soybean meal was substituted with an equivalent amount of 5% wet fermented soybean meal. The experiment was conducted over 42 days. The average daily gain （ADG）, average daily feed intake （ADFI）, and feed-to-gain （F/G） were calculated based on replicate. Blood samples were collected on the 21^st and 42^nd days of the experiment. The concentrations of serum immunoglobulin A （IgA）, immunoglobulin G （IgG）, immunoglobulin M （IgM）, D-lactic acid, endotoxin, and diamine oxidase （DAO） activity were measured using commercially available assay kits. After the experiment, two broilers from each replicate were randomly selected for slaughter, and their breast muscle samples were pooled. The intramuscular fat （IMF） content was measured using the Soxhlet extraction method, while the fatty acid composition was analyzed via gas chromatography. The feed cost and meat production cost of broilers were calculated based on feed intake and weight gain data. [Result]Compared with the control group, the final body weight, ADG, and ADFI of broilers in the experimental group were significantly （P< 0.05） increased, while the feed-to-gain ratio was marginally lower （P=0.051）. On the 21^st day of the experiment, the serum IgM content in the experiment group exhibited a significant increase （P<0.05）, and the content of IgA and IgG was significantly increased （P<0.01）. On the 42^nd day of the experiment, the serum concentrations of IgA, IgG, and IgM in the experiment group were significantly increased （P<0.01）. On the 21^st day of the experiment, the serum D-lactic acid and endotoxin content of the experiment group broilers were significantly reduced （P<0.01）. On the 42^nd day of the experiment, the serum diamine oxidase （DAO） activity and the endotoxin levels were markedly reduced （P<0.01）. There were no significant （P>0.05） differences in muscle fat （IMF）, muscle saturated fatty acids （SFA）, unsaturated fatty acids （UFA）, monounsaturated fatty acids （MUFA）, and polyunsaturated fatty acids （PUFA） between the control and experimental groups. When wet fermented soybean meal was used to replace an equivalent amount of soybean meal for feeding broilers, the cost of meat production could be reduced by 0.06 yuan/kg. [Conclusion] The substitution of 5% wet fermented soybean meal or an equivalent amount of conventional soybean meal significantly enhances the growth performance, immunity, and intestinal barrier functions of broilers, while also reducing the cost of meat production.

Key words: wet fermented soybean meal, broilers, sero-immunity, intestinal permeability, muscle fatty acid