Abstract
In vitro fermentation systems such as the rumen simulation technique (RUSITEC) are frequently used to assess dietary manipulations in livestock, thereby limiting the use of live animals. Despite being in use for nearly 40 years, improvements are continually sought in these systems to better reflect and mimic natural processes in ruminants. The aim of this study was to evaluate the effect of forage preparation, i.e., frozen minced (FM) and freeze-dried and ground (FDG), on the ruminal microbiota and on fermentation characteristics when included as a substrate in a RUSITEC system. A completely randomized design experiment was performed over a 15-day period, with 7 days of adaptation and an 8-day experimental period. Fermentation parameters (total gas, CH4, and volatile fatty acid production) were analyzed on a daily basis over the experimental period and the archaeal and bacterial microbiota (liquid-associated microbes [LAM] and solid-associated microbes [SAM] was assessed at 0, 5, 10, and 15 days using high-throughput sequencing of the 16S rRNA gene. Results from this study suggested a tendency (P = 0.09) of FM treatment to increase daily CH4 (mg/d) production by 16.7% when compared with FDG treatment. Of the major volatile fatty acids (acetate, propionate, and butyrate), only butyrate production was greater (P = 0.01) with FM treatment compared with FDG substrate. The archaeal and bacterial diversity and richness did not differ between the forage preparations, although feed particle size of the forage had a significant effect on microbial community structure in the SAM and LAM samples. The Bacteroidetes phylum was more relatively abundant in the FM substrate treatment, while Proteobacteria was enriched in the FDG treatment. At the genus-level, Butyrivibrio, Prevotella, and Roseburia were enriched in the FM substrate treatment and Campylobacter and Lactobacillus in the FDG substrate treatment. Evidence from this study suggests that forage preparation affects CH4 production, butyrate production, and the structure of the rumen microbiota during in vitro fermentation.
Highlights
MATERIALS AND METHODSReducing methane (CH4) emissions from anthropogenic activities is of considerable interest since enteric fermentation from ruminants accounts for 25% of the 40% derived from agriculture (Olivier et al, 1999; Steinfeld et al, 2006)
Total Volatile Fatty Acid (VFA), propionate, BCVFA, acetate to propionate ratio and pH were not affected by type of preparation, but there was a tendency of increase in daily CH4 production in frozen minced (FM) compared to freezedried and ground (FDG) (Table 2)
We examined the effect of FM vs. FDG forage preparation on CH4, total gas, and VFA production, and on the archaeal and bacterial microbiota, using a rumen simulation technique (RUSITEC) system
Summary
MATERIALS AND METHODSReducing methane (CH4) emissions from anthropogenic activities is of considerable interest since enteric fermentation from ruminants accounts for 25% of the 40% derived from agriculture (Olivier et al, 1999; Steinfeld et al, 2006). Ruminants are considered economically important due to their capacity to digest low-quality forages (Flint, 1997) and their ability to convert these substrates into energy is largely dependent on the rumen microbiota (i.e., bacteria, anaerobic fungi, protozoa, and methanogenic archaea) which converts indigestible plant material into usable energy for the host. This allows ruminants to produce milk, meat, wool, and leather without competing directly with humans for food (Buddle et al, 2011). It has been common practice to use forages in freezedried and ground (FDG) form as a substrate in these systems (Avila-Stagno et al, 2014), digestion products and kinetics are altered when fresh forage is used (Barrell et al, 2000)
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