Regulatory Effects of Eight Unconventional Protein Sources on Intestinal Microbiota and Odor Metabolism in Growing-Finishing Pigs: Implications for Environmentally Friendly Feed Development and Reduction of Soybean Meal Usage

To address the challenges of odor pollution from livestock farming and the need for resource conservation and reduced feed consumption, this study compared the effects of eight unconventional protein sources with soybean meal on the gut microbiota and metabolism of fattening pigs. The dephenolized cottonseed protein promoted the production of short-chain fatty acids, with total SCFAs increasing by 32.7% compared to the soybean meal. The palm kernel meal enhanced microbial diversity by enriching the Fournierella genus and increased butyric acid production. The abundance of Lactobacillus was negatively correlated with the generation of H2S and H2, while Megasphaera and Streptococcus were positively correlated with the production of sulfur-containing gases and isovaleric acid. The microbial metabolic activity in the functional pathway of cysteine and methionine in the sesame meal-Q group increased by 42.3%, positively regulating H2S emissions. The total gas production of the sunflower meal and sesame meal-J groups decreased by 15-22% compared to the soybean meal-K group, with the H2S emission of the sesame meal-J group decreased by 67%. Through the regulatory framework linking of "nutrition-microbiota-odor emissions", this study revealed the mechanism by which unconventional protein sources regulate the gut microbiota of fattening pigs to exert nutritional support and odor reduction effects. This finding provides a theoretical basis for the development of environmentally friendly feed and the reduction of soybean meal usage.