Effects of Penicillium chrysogenum-Fermented Cotton Straw on Lactation Performance, Serum Biochemical Parameters, and Rumen Microbiota in Saanen Dairy Goats

Cotton straw, a major agricultural residue in China, is underutilized for ruminant feed owing to its recalcitrant lignin barrier, which impairs palatability and in vivo digestibil-ity. Solid-state fermentation using ligninolytic fungi provides a sustainable strategy to upgrade this lignocellulosic biomass. Nevertheless, the physiological outcomes of feeding fermented cotton straw to lactating ruminants remain largely unexplored. Herein, we investigated the effects of cotton straw fermented by Penicillium chrysogenum YL-11 on milk production, serum biochemical profiles, and ruminal microbial community composition in Saanen dairy goats, together with a biosafety assessment of the strain using a murine model. A completely randomized design was employed, involving 30 Saanen dairy goats (2–3 parities, initial body weight 48.56 ± 4.74 kg, milk yield 1.03 ± 0.27 kg/d, days in milk 180 ± 5.82 d) randomly assigned to three groups (n = 10): control (CK1, no cotton straw), CK2 (20% unfermented cotton straw), and YL-11 (20% fermented cotton straw). The trial included a 7-day adaptation and a 60-day experimental period. The results demonstrated that YL-11 administration did not adversely affect organ indices, serum biochemistry, or immune parameters in mice (p > 0.05). In dairy goats, YL-11 significantly increased average daily milk yield and 4% fat-corrected milk yield (p < 0.01), while the feed-to-milk ratio was significantly lower than that of the CK2 group (p < 0.01), but did not differ significantly from the CK1 group. Apparent digestibility of crude protein and ash was significantly higher in the YL-11 group than in the CK2 group (p < 0.05), with no significant differences observed between the YL-11 and CK1 groups. Milk fat and lactose percentages were also increased in the YL-11 group compared with both control groups (p < 0.05). Antioxidant enzyme activities (T-AOC, SOD, CAT, GSH-PX) were elevated, whereas MDA, TNF-α, IL-1β, and TGF-β1 were decreased (p < 0.05). Rumen ammonia nitrogen and the acetate/propionate ratio were increased significantly (p < 0.05) and the abundance of fiber-degrading taxa, including Verrucomicrobiota was enriched in the YL-11 group, with five potential biomarkers identified by LEfSe analysis. In conclusion, P.chrysogenum YL-11 is safe and its fermented cotton straw improves lactation performance, rumen fermentation, antioxidant status, and fiber-degrading microbiota in dairy goats, offering a promising strategy for utilizing cotton straw as a feed resource.