Effects of rapeseed meal replacement of soybean meal on production performance, egg quality and gut microbiota in laying ducks

This study aims to evaluate the effects of replacing soybean meal with RM and adding high-dose choline to the soybean meal feed (as a positive control for choline effect) to soybean meal feed on production performance, fatty acid composition, sensory evaluation, antioxidant indicators and gut microbiota of laying ducks. A total of 216 Longyan Shan Partridge ducks were randomly divided into three groups: SM (corn-soybean diet), RM (corn-RM diet), and SC (SM diet supplemented with 2500 mg choline /kg). The study lasted 10 weeks. The results showed ducks fed the RM diet exhibited significantly lower egg production rate, egg weight, and daily egg mass (P < 0.01). In RM group, the expression abundance of Blautia and Desulfovibrio increased, which led to the expression of microbial TMA lyase genes CutC (1.29-fold) and CutD (1.74-fold) was significantly upregulated in cecal microbiota (P < 0.05). Concurrently, RM elevated egg trimethylamine (TMA) content (P < 0.05), with CutC/CutD expression positively correlated with TMA levels (r = 0.89, P < 0.01), and intensified fishy odor scores (P < 0.05). Additionally, RM reduced gut microbial diversity and the relative abundance of short-chain fatty acid-producing genera (e.g., Roseburia), and suppressed tryptophan metabolism. This discovery provides a theoretical basis for reducing soybean meal dependence, through nutritional regulation (such as adding CutC inhibitors).