Abstract: [Objective] To investigate the effects of replacing a portion of conventional soybean meal and wheat bran with fermented soybean meal in the basal diet on the production performance, egg quality, and health status of Hy-Line Brown laying hens during the late laying period, providing a basis for the rational application of fermented soybean meal in the diets of aging hens. [Methods] A total of 480 Hy-Line Brown laying hens aged 65 weeks old were selected and randomly assigned to two groups, with four replicates per group and 60 hens per replicate. The control group was fed a basal diet, while the experimental group received a diet where 5% fermented soybean meal replaced a portion of the conventional soybean meal and wheat bran under the condition of equal dietary nutritional levels. The pre-trial period lasted for 1 week, and the formal trial lasted 8 weeks. During the formal trial period, daily records were kept of the number of eggs laid, qualified egg weight, total feed intake, and mortality and culling number, and production performance indices, such as laying rate and average egg weight, were calculated. At the end of the trial, multiple egg quality indices were measured; blood samples were collected to determine lipid metabolism and antioxidant-related indices; organs were weighed to calculate visceral organ indices; and an economic benefit analysis was conducted based on market prices of materials. [Results] Compared with the control group, the experimental group showed significantly lower laying rates and average daily feed intake （P<0.05）, while the feed-to-egg ratio and mortality/culling rate exhibited a downward trend without significant differences （P>0.05）. The eggshell color L* and b* values were significantly increased （P<0.05）, with no significant differences observed in other egg quality parameters （P>0.05）. The net profit per hen increased by 0.12 RMB, indicating improved economic benefits. No significant differences were found in visceral organ indices, ovary weight, graded follicle weight, or the number of graded follicles and small yellow follicles （P>0.05）. Serum triglyceride （TG） levels significantly decreased （P<0.05）, whereas total cholesterol （T-CHO）, low-density lipoprotein cholesterol （LDL-C）, and high-density lipoprotein cholesterol （HDL-C） showed no significant differences （P>0.05）. Serum total antioxidant capacity （T-AOC） was significantly increased （P<0.05）, while catalase （CAT）, superoxide dismutase （SOD） activities, and malondialdehyde （MDA） content exhibited no significant differences （P>0.05）. [Conclusion] Under equal dietary nutrient levels, replacing a portion of soybean meal and wheat bran with 5% fermented soybean meal can improve lipid metabolism and antioxidant capacity, optimize eggshell color, and enhance economic benefits for Hy-Line Brown laying hens during the late laying period, without adverse effects on visceral organ development. Fermented soybean meal can serve as an alternative ingredient to conventional soybean meal in the diets of Hy-Line Brown laying hens during the late laying period.

Key words: fermented soybean meal, Hy-Line Brown laying hens during the late laying period, production performance, egg quality, lipid metabolism, antioxidant capacity