Abstract
The aim of the study was to investigate the effect of untreated and processed rapeseed meal (RSM) on fiber degradability by pig gut microbiota and the adaptation of the microbiota to the substrate, by using the Swine Large Intestine in vitro Model (SLIM). A standardized swine gut microbiota was fed for 48 h with pre-digested RSM which was processed enzymatically by a cellulase (CELL), two pectinases (PECT), or chemically by an alkaline (ALK) treatment. Amplicons of the V3–V4 region of the 16S rRNA gene were sequenced to evaluate the gut microbiota composition, whereas short chain fatty acids (SCFA) were measured to assess fiber degradation. Adaptive gPCA showed that CELL and ALK had larger effects on the microbiota composition than PECT1 and PECT2, and all substrates had larger effects than CON. The relative abundance of family Prevotellaceae was significantly higher in CELL treatment compared to other treatments. Regardless of the treatments (including CON), the relative abundance of Dorea, Allisonella, and FamilyXIIIUCG_001 (in the order of Clostridiales) were significantly increased after 24 h, and Parabacteroides, Mogibacterium, Intestinimonas, Oscillibacter, RuminococcaceaeUCG_009, Acidaminococcus, Sutterella, and Citrobacter were significantly higher in abundance at time point 48 compared to the earlier time points. Prevotella 9 had significant positive correlations with propionic and valeric acid, and Mogibacterium positively correlated with acetic and caproic acid. There was no significant difference in SCFA production between untreated and processed RSM. Overall, degradability in the processed RSM was not improved compared to CON. However, the significantly different microbes detected among treatments, and the bacteria considerably correlating with SCFA production might be important findings to determine strategies to shorten the fiber adaptation period of the microbiota, in order to increase feed efficiency in the animal, and particularly in pig production.
Highlights
Rapeseed meal (RSM) is an important alternative feed ingredient for protein-rich feeds, but rapeseed meal (RSM) is rich in nonstarch polysaccharides (NSP) (Pustjens, 2013; De Vries et al, 2014; Pustjens et al, 2014a)
Another report showed that microbial cellulase activity was only observed after a 6-week adaptation period when pigs were fed with different types of dietary fiber (8% sugar beet pulp, or 10% wheat bran) (Castillo et al, 2007)
There were 26839 ± 4458 (ALK), 26973 ± 5187 (CELL), 26243 ± 4871 (PECT1), 29597 ± 4026 (PECT2), and 52927 ± 4055 (CON) raw sequences obtained after Illumina Miseq sequencing
Summary
Rapeseed meal (RSM) is an important alternative feed ingredient for protein-rich feeds (where mainly soybean meal is used as protein source), but RSM is rich in nonstarch polysaccharides (NSP) (Pustjens, 2013; De Vries et al, 2014; Pustjens et al, 2014a). Previous studies showed that a high-fiber rapeseed diet did not results in a significant increase in SCFA content in the chyme of RSM-fed pigs after a 3-week adaptation period (Chen et al, 2018; Umu et al, 2018). SCFA-producing microbes, such as Dialister, Shuttleworthia, Bulleidia, Coprococcus, and Lachnospira, were detected more abundant in the colon of highfiber rapeseed pigs compared to those in the control pigs (Umu et al, 2018) This might be because the 3-week adaptation period was too short to have a considerable change in the metabolic function of SCFA-producing microbes, or more likely, the SCFA were rapidly utilized by the intestinal epithelium of the host. The optimal adaptation time should be evaluated case by case
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