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Background: Here, we aimed to investigate the effects of ensiled mulberry leaves (EML) and sun-dried mulberry fruit pomace (SMFP) on fecal bacterial communities in Simmental crossbred finishing steers. To this end, the steers were reared on a standard TMR diet, standard diet containing EML, and standard diet containing SMFP. The protein and energy levels of all the diets were similar. Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene and quantitative real-time PCR were used to analyze and detect the fecal bacterial community., Results: Most of the sequences were assigned to Firmicutes (56.67%) and Bacteroidetes (35.90%), followed by Proteobacteria (1.87%), Verrucomicrobia (1.80%) and Tenericutes (1.37%). The predominant genera were 5-7 N15 (5.91%), CF231 (2.49%), Oscillospira (2.33%), Paludibacter (1.23%) and Akkermansia (1.11%). No significant differences were observed in the numbers of Firmicutes (p = 0.28), Bacteroidetes (p = 0.63), Proteobacteria (p = 0.46), Verrucomicrobia (p = 0.17), and Tenericutes (p = 0.75) populations between the treatment groups. At the genus level, genera classified with high abundance (more than 0.1%) belonged primarily to Bacteroidetes and Firmicutes. Furthermore, no differences were observed at the genus level: 5-7 N15, CF231, Oscillospira, Paludibacter, and Akkermansia (p > 0.05 in all cases), except that rc4-4 was lower in the CON and SMFP groups than in the EML group (p = 0.02). There were no significant differences in the richness estimate and diversity indices between the groups (p > 0.16), and the different diets did not significantly influence most selected fecal bacterial species (p > 0.06), except for Ruminococcus albus, which was higher in the EML group (p < 0.01) and Streptococcus bovis, which was lower in the CON group (p < 0.01) relative to the other groups., Conclusions: In conclusion, diets supplemented with EML and SMFP have little influence on the fecal bacterial community composition in finishing steers.

Live yeast (Saccharomyces cerevisiae) constitutes an effective additive for animal production; its probiotic effect may be related to the concentrate-to-forage ratio (CTFR). The objective of this study was to assess the effects of S. cerevisiae (SC) on fiber degradation and rumen microbial populations in steers fed diets with different levels of dietary concentrate. Ten Simmental × Local crossbred steers (450 ± 50 kg BW) were assigned to a control group or an SC group. Both groups were fed the same basal diet but the SC group received SC supplementation (8 × 10(9) cfu/h/d through the ruminal fistula) following a two-period crossover design. Each period consisted of four phases, each of which lasted 17 d: 10 d for dietary adaptation, 6 d for degradation study, and 1 d for rumen sample collection. From the 1(st) to the 4(th) phase, steers were fed in a stepwise fashion with increasing CTFRs, i.e., 30:70, 50:50, 70:30, and 90:10. The kinetics of dry matter and fiber degradation of alfalfa pellets were evaluated; the rumen microbial populations were detected using real-time PCR. The results revealed no significant (P > 0.05) interactions between dietary CTFR and SC for most parameters. Dietary CTFR had a significant effect (P < 0.01) on degradation characteristics of alfalfa pellets and the copies of rumen microorganism; the increasing concentrate level resulted in linear, quadratic or cubic variation trend for these parameters. SC supplementation significantly (P < 0.05) affected dry matter (DM) and neutral detergent fiber (NDF) degradation rates (c DM, c NDF) and NDF effective degradability (EDNDF). Compared with the control group, there was an increasing trend of rumen fungi and protozoa in SC group (P < 0.1); copies of total bacteria in SC group were significantly higher (P < 0.05). Additionally, percentage of Ruminobacter amylophilus was significantly lower (P < 0.05) but percentage of Selenomonas ruminantium was significantly higher (P < 0.05) in the SC group. In a word, dietary CTFR had a significant effect on degradation characteristics of forage and rumen microbial population. S. cerevisiae had positive effects on DM and NDF degradation rate or effective degradability of forage; S. cerevisiae increased rumen total bacteria, fungi, protozoa, and lactate-utilizing bacteria but reduced starch-degrading and lactate-producing bacteria.