Effects of Protein Feed Ingredients on Odor and Carbon Emission in Nursery Pigs: An In Vitro Fermentation Study

Background Odor emissions from pig farming industry pose a risk to the environment and animal health. Although recent research has investigated the impacts of feed selection, waste treatment, and management on odor reduction, few studies have specifically addressed odor mitigation through the composition of feed ingredients. Results This study evaluated the effects of seven feed ingredients (soybean meal, rice bran meal, peanut meal, sesame meal, palm meal, sunflower meal, and dephenolized cottonseed protein) on the emission of odor and greenhouse gases, the production of short-chain fatty acids (SCFAs), and the regulation of the gut microbiota in nursery pigs via in vitro simulated fermentation. High-protein feeds such as soybean meal and dephenolized cottonseed protein produced more total gases and ammonia (NH ₃ ), whereas sesame meal-J resulted in the lowest gas production. The level of acetate from sesame meal-J was significantly lower than that from soybean meal-K. Lactobacillus , enriched in the sesame meal-J fermented group, was negatively correlated with H ₂ S and NH ₃ emissions through the suppression of nitrogen and sulfur metabolism but the activation of carbon metabolism functional pathways. In contrast, Megasphaera and Olsenella , which were enriched in the sesame meal-Q and defatted rice bran meal fermented groups, were positively correlated with H ₂ S and NH ₃ levels and presented opposite metabolic profiles. Conclusions This study determined the effects of seven feed ingredients on odor emissions and gut microbiota composition in finishing pigs. Increasing the proportion of sesame meal-J in the diet reduced odor emissions, thereby promoting ecological and low-carbon development of animal husbandry.