Frontiers in Animal Science (Sep 2021)

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

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

DOI
https://doi.org/10.3389/fanim.2021.715142
Journal volume & issue
Vol. 2

Abstract

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This study investigated the impact of carbohydrate source and fluid passage rate (dilution rate) on ruminal fermentation characteristics and microbial crude protein (MCP) formation. Three commonly used feeds (barley grain [BG], beet pulp [BP], and soybean hulls [SBH]), 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% [low] and 3.0% [high] of fermenter volume per h). This resulted in six treatments (tested in 3 runs): BGhigh, BGlow, BPhigh, BPlow, SBHhigh and SBHlow. The system was adapted for 7 d, followed by 4 d of sampling. Production of MCP (mg/g degraded organic matter [dOM]; estimated by 15N analysis) was greater with high dilution rate (DL; p < 0.001) and was higher for SBH compared to both BG and BP (p < 0.001). High DL reduced OM degradability (OMD) compared to low DL (p < 0.001), whereas incubation of BG resulted in higher OMD compared to SBH (p < 0.002). Acetate:propionate ratio decreased in response to high DL (p < 0.001). Total gas and methane production (both /d and /g dOM) were lower with high DL (p < 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.

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