Lactobacillus-driven feed fermentation regulates microbiota metabolism and reduces odor emission from the feces of pigs

Fermentation by Lactobacillus can increase the nutritional value of feed, which is advantageous for pig production. However, the effects of Lactobacillus-driven feed fermentation on the emission of odors from pig feces are unclear. Here, we evaluated how feed fermentation by Lactobacillus affects the concentration of odor molecules in feces (CO2, NH3, H2S, indole, and skatole) and analyzed the changes in fecal microbiota and metabolites during fecal storage. Pigs reared on fermented feed had a higher average daily gain (ADG) and lower feed-to-gain (F/G) ratio than the control group. By the 3rd and 5th days, the concentration of CO2 in feces from pigs in the fermentation group significantly decreased, and the contents of H2S, NH3, and skatole in the fermentation group were significantly lower than those in the control group on the 1st, 3rd, and 5th days of fecal storage. The fermentation group exhibited a higher Bacteroidetes abundance on the 3rd and 5th days. With prolonged fecal storage, the fermentation group exhibited a higher abundance of Weissella and Lactobacillus and a lower abundance of Streptococcus. The Lactobacillus fermentation group also showed lower levels of secondary amino acid metabolites, such as 6-hydroxyhexanoic acid and 5-aminopentanoic acid. The pure strain Weissella cibaria ZWC030, which could inhibit the production of skatole in vitro, was successfully isolated from the fermentation group. Overall, the study revealed the interrelationships among fecal microbiota, metabolites, and odor molecules. The findings provide a new avenue for the application of Lactobacillus-driven feed fermentation to promote ADG, decrease the F/G ratio in pigs during growth, and reduce environmental pollution.