Mei, Shihui, He, Guangxia, Chen, Ze, Zhang, Rong, Liao, Yixiao, Zhu, Mingming, Xu, Duhan, Shen, Yanjuan, Zhou, Bijun, Wang, Kaigong, Wang, Chunmei, Zhu, Erpeng, and Chen, Chao
Simple Summary: Feedstuff deficiency has forced researchers to find new natural alternatives. Distillers grain (DG) is a high-quality feed alternative due to its rich nutrients. However, the use of DG is limited in livestock diets due to the presence of some antinutritional compounds. The probiotic fermentation of DG can improve its nutritional composition, eliminating the antinutrient composition of DG. In this study, feeding with 15% probiotic-fermented distillers grains (PFDG) improved the antioxidant capacity, immune status, and rumen enzyme activity, without affecting the ADG, of finishing cattle, regulating rumen microbiota abundance and showing a positive effect on rumen phenylalanine metabolism, tryptophan metabolism, and pyrimidine metabolism. The current results indicate that PFDG could be incorporated, at a 15% inclusion rate, into the diet in finishing cattle. A total of 30 Simmental crossbred cattle (6.50 months old, 265.0 ± 22.48 kg) were randomly divided into three groups, with 10 heads per group, and fed for 45 days. The diet treatments consisted of the Control group without PFDG supplementation, the PFDG-15% group with 15% PFDG substituting for 15% concentrate, and PFDG-30% group with 30% PFDG substituting for 30% concentrate. The results showed that compared with the Control group, the average daily gain (ADG) of the cattle in the PFDG-30% group decreased significantly (0.890 vs. 0.768 kg/d, p = 0.005). The serum malondialdehyde content of cattle in the PFDG-15% and PFDG-30% groups decreased significantly (p = 0.047) compared to that of the Control group. However, the serum superoxide dismutase activity of cattle in the PFDG-30% group was significantly higher than that of the Control group (p = 0.047). Meanwhile, both the PFDG-15% and PFDG-30% groups (1758.47 vs. 2061.30 μg/mL) showed higher serum levels of immunoglobulin G, while the interleukin-10 concentration was lower in the PFDG-30% group (p = 0.027). In addition, the PFDG-15% and PFDG-30% groups shifted the rumen microbiota by improving the abundances of F082 (related to propionic acid production) and fiber-degrading bacteria (Lachnospiraceae_UGG-009 and Prevotellaceae_UCG-001) and reducing the abundance of the disease-associated bacteria Selenomonas. A Kyoto encyclopedia of genes and genomes (KEGG) analysis illustrated that three key metabolic pathways, including phenylalanine metabolism, pyrimidine metabolism, and tryptophan metabolism, were enriched in the PFDG-15% group, but eight key metabolic pathways, including arachidonic acid metabolism, were enriched in the PFDG-30% group. Importantly, both the PFDG-15% and PFDG-30% groups increased (p < 0.01) the activities of cellulase, lipase, and protease in the rumen. Finally, the different bacterial abundance in the rumen was associated with changes in the ADG, serum antioxidant capacity, immune status, rumen enzyme activity, and metabolites. These results suggest that PFDG alters rumen microbiome abundance, metabolome, and enzyme activity for enhancing serum antioxidant capacity and the immune status, but when the supplemental level reaches 30%, it has a negative effect on ADG and the anti-inflammatory factors in finishing cattle. [ABSTRACT FROM AUTHOR]