Extruded Spirulina with enzyme supplementation improves broiler performance via gut microbiota and duodenal proteome remodelling

This study evaluated the processing and enzyme supplementation of Spirulina (Limnospira platensis) as a broiler feed ingredient by assessing growth, the duodenal proteome, and caecal microbiota. 120 Ross 308 broilers (21–35 days) were assigned to one of the four experimental diets: maize–soybean control (CTR); 15% unprocessed L. platensis (MA); 15% extruded L. platensis (MAE); or MAE plus 0.21% pancreatin–lysozyme (MAEM). MA birds showed ~30% lower daily gain and a 22% poorer feed conversion ratio (FCR) versus CTR, driven by reduced feed intake, whereas MAEM restored performance (ADG: 49.7 vs. 57.3 g/day; FCR: 2.13 vs. 1.90). Duodenal proteomics (false discovery ratio < 1%, ≥ 2 unique peptides) identified seven differentially abundant proteins related to extracellular matrix remodelling (COL12A1, LAMA4) and lipid metabolism (ETFA, SLC27A2). MAE showed increased abundance of COL12A1 and LAMA4, indicating enhanced mucosal integrity, while MA induced lipid-metabolism enzymes as a compensatory response. Caecal 16S rRNA profiling showed that MAE and MAEM selectively enriched fibre-degrading and short-chain fatty acids-producing taxa (e.g. Bacteroides, Christensenellaceae ), confirming distinct community clustering by diet. These findings demonstrate that extrusion with/without enzymes improves nutrient bioaccessibility and gut function of L. platensis in broiler diets, supporting its use as a sustainable alternative protein source. • Extruded L. platensis showed similar growth performance metrics as CTR diet. • Gut proteomics identified seven differentially abundant proteins. • Gut microbiota with extrusion enriching fibre-degrading and SCFA-producing taxa • Extrusion improves nutrient bioaccessibility and gut function of L. platensis .