A diet containing Cyberlindnera jadinii yeast as a protein source demonstrates comparable benefits to a formic acid and probiotic supplemented diet in post-weaning piglets

The increasing demand for sustainable protein sources in livestock production necessitates the evaluation of novel feed ingredients that can reduce environmental impact while maintaining animal health and performance. The effects of replacing soybean meal with Cyberlindnera jadinii, a locally produced microbial yeast protein, in the diet of post-weaning piglets under commercial production conditions were analyzed. A total of 840 piglets were enrolled in a field experiment conducted over 3 consecutive production periods. Piglets were allocated to 2 dietary treatments: a control diet containing soybean meal, formic acid products and a probiotic, and an experimental diet where C. jadinii yeast replaced 45% of the dietary protein. Growth performance, fecal consistency, and gut microbiota composition were evaluated over a 4 wk post-weaning period. Piglets fed the yeast-based diet exhibited an overall lower average daily gain (ADG; P < 0.01) and average daily feed intake (ADFI; P < 0.01) compared to those on the control diet, while feed conversion ratio (FCR) remained similar between groups. No differences in fecal consistency or clinical signs of diarrhea were observed, indicating maintained gut health despite reduced feed intake. Microbiota profiling revealed dietary effects on microbial diversity and composition in both the ileum and colon. Notably, the yeast-fed piglets showed greater relative abundances of Lactobacillus johnsonii, Streptococcus gallolyticus, and members of the Prevotellaceae family, while the control-fed piglets had greater abundances of Lactobacillus amylovorus and Blautia hansenii. These findings indicate that C. jadinii yeast can partially replace soybean meal and formic acid in weaner pig diets without compromising health status, although some reduction in growth performance was observed. The altered gut microbiota, including enrichment of beneficial taxa such as L. johnsonii, suggests functional modulation of gut health, supporting the potential of yeast-based proteins as a sustainable feed strategy in pig production systems.