Effects of soybean meal fermented by endogenous lactic acid bacteria in birds and yeast on growth performance，immune organ index and intestinal health of broilers

<bold>Objective</bold> Soybean meal fermented by probiotics can improve the nutritional value，protein digestibility and utilization rate of soybean meal.Fermentation strain is the key factor affecting the fermentation effect of soybean meal.The purpose of this study is to explore the effects of soybean meal fermented by endogenous lactic acid bacteria in birds on related indexes of yellow-feather broilers，which can provide a theoretical basis for the development and use of compound bacteria fermented soybean meal in animal husbandry. <bold>Method</bold> 90 37-day-old yellow-feathered broilers with similar beginning weights were randomly assigned to three groups，with 15 replicates in each group and 2 broilers in each replicate.The experimental groups included the control group（fed with the basal diet），chicken endogenous lactobacillus group（the basal diet added with 0.5% monoclonal lactobacillus fermented soybean meal）and the group of compound bacterial （the basal diet added with 0.5% lactobacillus and yeast combination fermented soybean meal）.The preliminary test period was 3 days，and the formal test period was 28 days.During the experiment，the growth performance of all groups was measured.The bursa of fasciola，liver，pancreas，and spleen index，as well as intestinal length，weight，and pH，were measured for both the control group and the compound bacteria group.HE staining was performed on the duodenum，then the height of the duodenal villi，the depth of the crypts，as well as the villus-crypt ratio were compared and analyzed.qPCR was used to determine the relative expression of inflammatory factors mRNA in the cecum mucosa. <bold>Result</bold> （1）Compared with the control group，the average daily weight gain （ADG）of broilers in the fermented soybean meal group with compoound bacteria significantly increased（<italic>P</italic>&lt;0.05），the average daily feed intake（ADFI）showed a tendency to increase（<italic>P</italic>=0.053），and the overall effect was better than that of the group using soybean meal fermented by chicken endogenous Lactobacillus alone.，However，there were no significant differences in the feed conversion ratio（F/G）between the two groups and the control group （<italic>P</italic>&gt;0.05）.（2）Compared with the control group，the group fed with soybean meal fermented by compound bacteria significantly increased the abdominal fat rate of broiler chickens（<italic>P</italic>&lt;0.05），and there was a tendency to increase the bursa of Fabricius index （<italic>P</italic>=0.059）.However，it had no significant effects on the liver index，pancreas index and spleen index （<italic>P</italic>&gt;0.05）.（3）The pH of the ileum contents was decreasing （<italic>P</italic>=0.081），and the weight/length of the cecum had the tendency to rise （<italic>P</italic>=0.084）.There was no significant effects on the length of the cecum，cecum index，colorectal length，duodenal content pH，or cecal content pH （<italic>P</italic>&gt;0.05）.（4）There was no significant effects on the height of the duodenal villi，the depth of the crypt，or the villi to crypt ratio （<italic>P</italic>&gt;0.05）.（5）The relative expression level of <italic>IL-6</italic> mRNA in the cecal mucosa was significantly increased （<italic>P</italic>&lt;0.05），the relative expression level of <italic>IL-10</italic> mRNA was significantly decreased （<italic>P</italic>&lt;0.05），and there was a trend of increased relative expression level of <italic>IL-8</italic> mRNA（<italic>P</italic>=0.064）.However，the relative expression levels of <italic>IL-1β</italic>，<italic>IL-2</italic>，<italic>IL-4</italic>，<italic>IFN-α</italic>，<italic>IFN-β</italic>，<italic>IFN-γ</italic> and <italic>TNF-α</italic> were not significantly affected（<italic>P</italic>&gt;0.05）. <bold>Conclusion</bold> Adding 0.5% compound bacteria fermented soybean meal to the feed can significantly increase the average daily weight gain and abdominal fat rate of broilers.It also has the tendency to lower the pH of ileum contents and increase the bursa index of broilers.