AUTHOR=Pfau Friederike , Hünerberg Martin , Südekum Karl-Heinz , Breves Gerhard , Clauss Marcus , Hummel Jürgen 

TITLE=Effects of Dilution Rate on Fermentation Characteristics of Feeds With Different Carbohydrate Composition Incubated in the Rumen Simulation Technique (RUSITEC)

JOURNAL=Frontiers in Animal Science

VOLUME=2

YEAR=2021

URL=https://www.frontiersin.org/journals/animal-science/articles/10.3389/fanim.2021.715142

DOI=10.3389/fanim.2021.715142

ISSN=2673-6225

ABSTRACT=<p>This study investigated the impact of carbohydrate source and fluid passage rate (dilution rate) on ruminal fermentation characteristics and microbial crude protein (<bold>MCP</bold>) formation. Three commonly used feeds (barley grain [<bold>BG</bold>], beet pulp [<bold>BP</bold>], and soybean hulls [<bold>SBH</bold>]), which differ considerably in their carbohydrate composition, were incubated together with a mixture of grass hay and rapeseed meal in two identical Rusitec apparatuses (each 6 vessels). Differences in fluid passage rate were simulated by infusing artificial saliva at two different rates (1.5% [<bold>low</bold>] and 3.0% [<bold>high</bold>] of fermenter volume per h). This resulted in six treatments (tested in 3 runs): <bold>BGhigh, BGlow, BPhigh, BPlow, SBHhigh</bold> and <bold>SBHlow</bold>. The system was adapted for 7 d, followed by 4 d of sampling. Production of MCP (mg/g degraded organic matter [<bold>dOM</bold>]; estimated by <sup>15</sup>N analysis) was greater with high dilution rate (<bold>DL</bold>; <italic>p</italic> &lt; 0.001) and was higher for SBH compared to both BG and BP (<italic>p</italic> &lt; 0.001). High DL reduced OM degradability (<bold>OMD</bold>) compared to low DL (<italic>p</italic> &lt; 0.001), whereas incubation of BG resulted in higher OMD compared to SBH (<italic>p</italic> &lt; 0.002). Acetate:propionate ratio decreased in response to high DL (<italic>p</italic> &lt; 0.001). Total gas and methane production (both /d and /g dOM) were lower with high DL (<italic>p</italic> &lt; 0.001). In our study increasing liquid passage rate showed the potential to increase MCP and decrease methane production simultaneously. Results encourage further studies investigating these effects on the rumen microbial population.</p>