Effects of adding lactic acid bacteria on the quality of mixed silage of whole-plant corn and Yunnan safflower stems and leaves

To fully utilize safflower (Carthamus tinctorius) by-products and determine the optimal ratio of whole-plant corn (Zea mays) mixed with safflower stems and leaves for silage with the addition of lactic acid bacteria, this study designed four treatments: whole-plant corn to safflower stems and leaves ratios of 100:0 (CK), 90:10 (T₀), 80:20 (T₁), and 70:30 (T₂). Each treatment had three replicates. After 60 days of sealed fermentation in tanks, the tanks were opened, and samples were collected to assess fermentation quality, nutritional value, and microbial composition. The results showed excellent sensory evaluation of silage across all mixing ratios. The pH values of all treatment groups ranged from 3.63 to 3.65 after silage fermentation, with no significant differences (P > 0.05). The ammoniacal nitrogen content was highest in the T1 group, reaching 0.016%. The lactic acid and acetic acid contents decreased as the proportion of safflower stems and leaves increased, while the propionic acid content in the T₀ group reached 0.17%, which was significantly higher than in the other treatment groups (P < 0.05). The butyric acid content in the T₂ group was 0.57%, significantly higher than in the other groups (P < 0.05). Nutritionally, crude ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), and calcium (Ca) content were positively correlated with the proportion of safflower stems and leaves, whereas crude fat and phosphorus (P) content decreased with increasing safflower stems and leaves. The T₁ group had the highest dry matter content (33.91%), while the T₀ group had the highest crude protein content (7.53%) and received the highest comprehensive evaluation score using the affiliation function method. Regarding the microbial community, at the bacterial phylum level, the dominant bacterial group in all treatments was Firmicutes. At the bacterial genus level, the dominant bacterial group in the T₁ treatment was an undefined Chlorobium genus, whereas Lactobacillus was predominant in the other treatment groups. A comprehensive analysis indicated that the optimal mixing ratio of whole-plant corn to safflower stems and leaves was 90:10, making it a viable option for production applications.