Effects of different levels of chili straw on growth performance, rumen fungal flora structure, function and economic benefits of sheep

As a crop residue, chili stalk can be used as an unconventional feed resource in animal production, exhibiting potential value in regulating animal health. This study investigated the effects of dietary chili straw supplementation on the growth performance, rumen fungal community structure, and metabolic function in sheep. Thirty finishing sheep (3-4 months old) with comparable body weights were randomly divided into 3 groups (n = 10) and fed diets containing 0%, 10%, and 20% capsicum straw (CS) for 63 days, including a 7-day adaptation period. At the end of the trial, body weights were recorded and rumen fluid samples were collected to assess growth performance, rumen fungal diversity, and functional profiles. Key findings include:(1) Dry matter intake (DMI) increased significantly in the 10% CS group (P < 0.01), whereas DMI and final body weight decreased in the 20% CS group (P < 0.01 or P < 0.05); Final body weight and average daily gain (ADG) showed an upward trend in the 10% CS group (P > 0.05), while ADG displayed a downward trend in the 20% CS group (P > 0.05); (2) The ACE and Chao1 indices were significantly elevated in the 20% CS group (P < 0.05); (3) Principal coordinates analysis (PCoA) and non-metric multidimensional scaling (NMDS) revealed distinct clustering of the 20% CS group compared to the control (CON) group; (4) Relative abundances of Ascomycota and Cladosporium increased, whereas those of Basidiomycota and Kazachstania decreased in CS-supplemented groups (P > 0.05); (5) FUNGuild functional prediction indicated that rumen fungi were predominantly symbiotrophic, with increased relative abundances of symbiotrophic and pathotrophic fungi and decreased saprotrophic fungi in CS groups (P > 0.05).In conclusion, incorporating 10% CS into sheep diets as an unconventional forage modulates rumen fungal communities and enhances rumen ecosystem stability, whereas exceeding 10% adversely affects feed intake and growth performance.