The aim of this experiment was to investigate the effects of partially replacing soybean meal with yeast powder in the diet on the growth performance, apparent nutrient digestibility, serum parameters, and gut microbiota of weaned pigs. A total of 64 commercial pigs of the ‘Duroc × Landrace × Large White’ crossbreed, with an average age of 50 days and a body weight of 19. 8 ± 1. 6 kg, were selected and randomly divided into four groups, each comprising 16 replicates. The pigs were fed either a control diet or experimental diets in which soybean meal was partially replaced by yeast powder at levels of 3% (LYP), 6% (MYP), and 9% (HYP), respectively, over a 26-day trial period. The results showed that replacing soybean meal with yeast powder significantly reduced the final body weight, average daily weight gain, average daily feed intake, and apparent digestibility of dry matter and crude ash in weaned pigs, while increasing the feed-to-gain ratio (p < 0. 05) ; it also increased serum total antioxidant capacity and glutathione peroxidase activity (p < 0. 05) and increased serum urea nitrogen and triglyceride levels, while reducing glucose and albumin levels in the HYP group (p < 0. 05). Concurrently, the replacement of soybean meal with yeast powder reshaped the gut microbiota structure; the MYP group exhibited the highest α-diversity, with increased abundance of the Firmicutes phylum. The LYP group was specifically enriched with the Streptococcus and Lactobacillus genera, while the MYP group was specifically enriched with an unclassified genus within the family Selenomonadaceae, and the HYP group was enriched with the Actinobacteriota and ClostridiaUCG₀14. Low- and medium-dose yeast powder supplementation was associated with enhanced antioxidant indices and distinct alterations in gut microbial composition compared with the control group; however, these changes occurred alongside reductions in growth performance; the optimal dose of yeast powder to replace soybean meal under the conditions of this trial requires further investigation.
Tang et al. (Mon,) studied this question.