Effects of Fungal Probiotics on Rumen Fermentation and Microbiota in Angus Cattle

The potential of fungal probiotics as ruminant feed additives has not been extensively studied. This study aimed to evaluate the effect of A. oryzae and T. longibrachiatum supplementation on Angus cattle during the early stages of fattening. In this study, 80 Angus cattle aged approximately 9~10 months (40 males and 40 females), with an average initial body weight (BW) of 276.46 ± 27.92 kg, were randomly assigned to four groups. Each group included 4 replicates (2 replicates of males and 2 replicates of females). Each replicate contained 5 male or 5 female Angus cattle. Cattle in the control group received a total mixed ration (TMR) without additives, while those in test groups 1, 2, and 3 received a TMR supplemented with complex probiotics (CPs) at 1.0, 2.0, and 3.0 g·kg^-1 of feed dry matter (DM), respectively. The adaptation and experimental periods were 7 and 60 days, respectively. Compared with those in the control group, the apparent digestibility of ether extract, calcium, and acid detergent fiber (ADF) was higher in test group 3. Test group 2 exhibited increased apparent digestibility of hemicellulose. Meanwhile, test group 3 exhibited increased levels of acetate, propionate, butyrate, and total volatile fatty acids and decreased pH. CPs increased the abundance of the SR1 phylum, Solibacillus, Lysinibacillus, and Planococcaceae_Bacillus and decreased the proportions of Lactococcus, Ruminococcus, and Ophryoscolex. Solibacillus was associated with the apparent digestibility of CP, Ca, and ADF. Planococcaceae_Bacillus was associated with increased apparent digestibility of CP, ADF, and hemicellulose. This suggests that CPs improve crude protein and cellulose digestion by increasing the proportions of Solibacillus and Planococcaceae_Bacillus. Therefore, the optimal CP dietary supplementation dose for Angus cattle was 3 g·kg^-1 of DM.