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Precision dietary interventions (e.g., altering proportions of dietary protein fractions) has significant implications for the efficiency of nutrient use in ruminants, as well as lowering their environmental footprint, specifically nitrogen (N) emissions. Soluble protein (SP) is defined as the protein fraction that is rapidly degraded in the rumen (e.g., non-protein N and true protein), and our previous study found that regulating SP levels could improve N efficiency in Hu sheep. Thus, the present study was conducted to explore in vitro how protein fractions with different SP levels modulate the rumen microbial community and its association with N metabolism. Four dietary treatments with different SP proportions and similar crude protein (CP) content (~14%) were formulated (% of CP): 20 (S20), 30 (S30), 40 (S40) and 50 (S50). Results showed that NH3-N content increased with increasing SP levels at 4, 12 and 24 h; TVFA, acetate, propionate and valerate were higher in S30 and S40 (p < 0.05) and had quadratic effects (p < 0.05). Moreover, dry matter digestibility (DMD) and N digestibility (ND) were all decreased with S20 and S50 (p < 0.05). The S30 and S40 treatments increased the abundance of Bacteroidetes and Prevotella (Prevotella_ruminicola) but decreased the abundance of Firmicutes and Proteobacteria (p < 0.05). Bacterial pathways related to amino acid and fatty acid metabolism also were enriched with S30 and S40. The abundance of Entodinium was increased with S30 and S40 and had a positive correlation with Prevotella, and these two genera also played an important role in N metabolism and VFA synthesis of this study. In conclusion, bacterial and protozoal communities were altered by the level of SP (% of CP), with higher SP levels (~50% of CP) increasing the microbial diversity but being detrimental to rumen N metabolism.

Background: Urtica cannabina, an unconventional forage, is widely distributed in northern China. It has high nutritional values that make it suitable for the ruminant’s feeding requirments as compared to Leymus chinensis. The current study was designed to evaluate varying ratios of Urtica cannabina and Leymus chinensis in the feeding diet and to see the effects on rumen fermentation and gas production in vitro. Methods: The study was designed into five treatments based on the different ratios of U. cannabina and L. chinensis: 0:100, 30:70, 50:50, 70:30 and 100:0 categorized into five groups from A-E. To detect the rumen fermentation parameters, the culture medium was collected at 1, 3, 6, 12 and 24 h. Result: Gas production of groups A and C was increased than other groups at 24h (P less than 0.05), whereas the rate of gas production (c) was also increased in group A (P less than 0.05). The pH values at 1, 3, 6 and 24 h were increased in groups A and C with higher values in group C at 24h (P less than 0.05). The ammonia concentration was increased in groups D and E at 3, 6, 12 and 24 h, with the lower values in group C at 24h (P less than 0.05). The concentration of bacterial and protozoal proteins was also observed higher in groups A and C at 1 and 24 h, with highest value in group C at 24 h (P less than 0.05). In summary, as for Urtica cannabina to Leymus chinensis ratios are concerned, 50:50 is an optimal ratio for rumen fermentation in vitro, which increases the gas production and microbial protein synthesis.

The effects of rice straw silage with combined additives (RSSA) of Lactobacillus plantarum, Trichoderma viride and wheat bran on growth performance, digestibility and rumen fermentation in growing lambs were investigated. Twelve growing lambs with initial body weight (BW ± SD) of 12.8 ± 0.4 kg were selected and randomly divided into 2 groups. These lambs were fed with rice straw silage (25%, on the dry matter intake (DMI) without additives (RSSW) and 25% RSSA supplementation respectively. The growth performance, nutrients digestibility and rumen fermentation parameters of growing lambs were determined. The results of this study showed that the average daily gain (ADG) and the feed conversion ratio (FCR) were significantly increased by the RSSA supplementation as compared to the RSSW supplementation (P gt 0.05). The apparent digestibility of dry matter (DM), as well as neutral detergent fiber (NDF) and acid detergent fiber (ADF) was significantly increased by RSSA supplementation (Pandlt;05). Moreover, the microbial crude protein (MCP), total volatile fatty acids (TVFA), acetate, butyrate and valeric acid concentrations in rumen fluid were significantly enhanced by the RSSA supplementation (P0andlt;05). In conclusion, rice straw silage with L. plantarum, T. viride and wheat bran can enhance the overall growth performance, rumen fermentation and apparent digestibility of nutrients in the growing lambs.

The study was conducted in vitro to investigate the effects of different ratios of Urtica cannabina and Leymus chinensis on fiber microstructure and digestibility in ruminal fluid. The experiment was divided into five groups based on the U. cannabina/L. chinensis ratios: A (0:100), B (30:70), C (50:50), D (70:30), and E (100:0). The culture medium was collected at 0, 1, 3, 6, 12, and 24 h. The results showed that: (1) in vitro crude protein degradability (IVCPD) was higher in group A, whereas in vitro neutral detergent fiber degradability (IVNDFD) was higher in group C (p &lt, 0.05), (2) protozoa count was increased from 1 h to 3 h and decreased afterwards, with significant differences observed in several genera (p &lt, (3) microbial crude protein (MCP) contents at 1, 3, 6, and 24 h were higher in groups A and C (p &lt, (4) the basic tissue of U. cannabina was gradually degraded. At 24h, the secondary xylem vessel structure was observed in groups B and C, but not in groups D and E. In summary, there was higher neutral detergent fiber (NDF) digestibility, higher rumen MCP contents, and lower protozoa count, showing the significance of the 50:50 ratio for microbial growth and fiber digestibility.