Background Mannan oligosaccharides (MOS) are a promising feed additive in animal husbandry due to mainly improving animal health status. The purpose of this study was to investigate the effects of MOS on growth performance, nutrient digestibility, ruminal fermentation, and twelve hematological parameters in sheep. Methods Ninety-six healthy Hu rams with similar body weights were chosen and divided into four treatment groups (twenty-four rams in each group), in which four different doses of MOS were tested: 0%, 0.8%, 1.6% and 2.4% of the basal diet (on an as-fed basis). Results The results showed that supplementation dietary MOS did not affect feed intake, body weight, average daily weight gain, or ruminal short-chain fatty acids (SCFAs) concentration; the ratio of individual fatty acids to total SCFAs, the C2/C3 ratio, and the hematological parameters in the sheep were also unaltered (P > 0.05). Conversely, supplementation dietary MOS increased the dry matter, organic matter, crude protein, neutral detergent fiber, acid detergent fiber, and ash apparent digestibility (P < 0.05), and decreased the ruminal ammonia concentration in the sheep (P < 0.05), especially at a dose of 1.6%. Conclusions This indicates that supplementation dietary MOS improved nutrient utilization by the sheep and nitrogen metabolism in the rumen; however, the effects are too slight to interfere with the basal metabolism in the sheep.

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The pelleted TMR pulverized the grass during processing, which may result in more solid attached microorganisms in the filtered rumen fluid. The objective of this study was evaluating the necessity of distinguishing physical phases of rumen contents for analysis of prokaryotes communities in rumen of lambs fed pelleted TMR, considering the dissimilarity of diversity and community of bacteria and archaea between fluid and mixed rumen contents. The yield of microbial DNA, bacterial diversity, abundances of fibrolytic bacteria of phylum Fibrobacterota and Spirochaetota, as well as genus Ruminococcus, Lachnospiraceae_NK3A20, Fibrobacter, and F082, and abundance of archaeal Methanimicrococcus in rumen fluid were lower than those in mixed phase of rumen contents (p ≤ 0.05). In conclusion, it is necessary to consider rumen content physical phases when studying the prokaryotic community in rumen of lambs fed pelleted TMR.

Background: Starch has faster rate of rumen fermentation than fiber, and always causes a rapid increase in ruminal molecular hydrogen (H2) partial pressure and microbial protein synthesis, which may promote other H2 sinks to compete H2 from methanogenesis. The study was designed to investigate the effects of increasing starch content on methane (CH4), hydrogen gas (gH2) production, rumen fermentation, metabolic hydrogen ([H]) production, microbial protein (MCP) synthesis through in vitro ruminal batch incubation. Methods: Seven different treatments was prepared by replacing corn straw with corn grain, and starch content were 72, 185, 297, 410, 525, 634 and 747 g/kg DM.Results: Elevating starch content increased DM degradation (Plinear < 0.001), and decreased the CH4 (Plinear and Pquadratic < 0.001) and gH2 (Plinear < 0.001) productions relative to DM degraded. Elevating starch content increased VFA concentration (Plinear < 0.001), propionate molar percentage (Plinear < 0.001; Pquadratic = 0.001) and MCP concentration (Plinear and Pquadratic < 0.001), and decreased acetate molar percentage (Plinear < 0.001), acetate to propionate ratio (Plinear < 0.001) and estimated net [H] production relative to DM degraded (Plinear < 0.001). Elevating starch content decreased molar percentage of [H] utilized for CH4 (Pquadratic = 0.003) and gH2 (Plinear < 0.001) production. Conclusion: Increasing starch content alters rumen fermentation pathway from acetate to propionate production with reduction in efficiency of [H] production, promotes H2 utilization with enhanced MCP synthesis and leads to the reduction in efficiency of CH4 and gH2 production.

Grain starch has a faster rate of rumen fermentation than straw fiber and causes a rapid increase in ruminal molecular hydrogen (H2) partial pressure, which may promote other H2 sinks to compete H2 away from methanogenesis. The study was designed to investigate the effects of increasing ratios of grain starch to straw fiber on hydrogen allocation and methanogenesis through in vitro ruminal batch incubation. Corn grain and corn straw were employed as starch and fiber source respectively. Seven treatments were the ratios of corn grain to corn straw (RGS) being 0:6, 1:5, 2:4, 3:3, 4:2, 5:1, and 6:0. Elevating RGS increased dry matter (DM) degradation and decreased methane (CH4) and hydrogen gas (gH2) production relative to DM degraded. Elevating RGS increased volatile fatty acid (VFA) concentration, propionate molar percentage and microbial protein (MCP) concentration, decreased acetate molar percentage, acetate to propionate ratio and estimated net metabolic hydrogen ([H]) production relative to DM degraded. Elevating RGS decreased the molar percentage of [H] utilized for CH4 and gH2 production. In summary, increasing ratios of grain starch to straw fiber altered rumen fermentation pathway from acetate to propionate production, reduced the efficiency of [H] production with the enhancement of MCP synthesis, and led to a reduction in the efficiency of CH4 and gH2 production.