Inclusion of different levels of fermented elephant grass in broiler chicken diet: effects on growth, physiology, carcass traits and gut microbial community

The physiological and microbiome-modulating benefits of dietary forage in monogastrics are impeded by recalcitrant fiber and anti-nutritional factors. However, fermentation and appropriate inclusion levels may overcome these limitations. This study evaluated the effects of two fermented cultivars of elephant grass (<i>Cenchrus purpureus</i> cv. Guiminyin and cv. Purple) incorporated into broiler diets at different inclusion levels, with emphasis on cultivar-specific responses, growth performance, physiological status, and gut microbial composition. A total of 240 male (30-days old) Jinling earth-neck chickens were housed in four replicate pens of 12 birds each, and randomly assigned to five dietary treatments (48 birds per treatment): a control diet with no inclusion (0%), CpGui5 (5% Guiminyin inclusion), CpGui10 (10% Guiminyin inclusion), CpPur5 (5% Purple inclusion), and CpPur10 (10% Purple inclusion). CpGui5 and Control diets had statistically similar and higher final weight, total weight gain, average daily gain and feed efficiency which were higher than the other treatments (P < 0.05). On the other hand, Control, CpGui5 and CpPur5 had higher daily feed intake compared to CpGui10 and CpPur10 which had the lower daily feed intake (P < 0.05). Slaughter performance revealed significant differences (P < 0.05), with the control, CpGui5, CpPur5 and CpPur10 groups maintaining higher live weight, dressed weight, half-bore, and breast muscle rate while CpGui10 recorded the lowest values. Blood biochemical indices, including total protein, albumin, liver enzymes, and renal function markers, were unaffected by dietary treatments (P > 0.05), indicating no adverse physiological effects. Gut microbiome analysis showed stable richness (Chao1, ACE) across treatments, while diversity (Shannon, Simpson) was reduced in CpPur5 relative to other groups (P < 0.05). A shared core microbiome of 202 OTUs was detected across all treatments, alongside treatment-specific enrichment of taxa. LEfSe (Linear Discriminant Analysis Effect Size) analysis identified treatment-specific enrichment of functionally relevant bacterial genera, including <i>Megamonas</i> in CpGui5 and <i>Ruminococcaceae_UCG-014</i> and unclassified <i>Lachnospiraceae</i> at higher inclusion levels (CpGui10). Overall, moderate inclusion of fermented elephant grass, especially CpGui5 supports broiler performance while maintaining physiological health and gut microbial stability, highlighting its potential as a sustainable functional feed resource for poultry production.