NAKANO Miwa

OGURA Shin-ichiro

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NAKANO, Miwa

OGURA, Shin-ichiro

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Effect of Plant-species Richness on MicrobialComposition and Rumen Function著者 NAKANO Miwa, OGURA Shin-ichirojournal orpublication titleJournal of Integrated Field Sciencevolume 14page range 33-37year 2017-03URL http://hdl.handle.net/10097/0012122233JIFS, 14 : 33 ? 37 (2017)Effect of Plant-species Richness on Microbial Composition and Rumen FunctionMiwa NAKANO1 and Shin-ichiro OGURA21Institute of Livestock and Grassland Science, NARO, Japan.Present: Western Region Agricultural Research Center, NARO, Japan.2Graduate School of Agricultural Science, Tohoku University, Japan.Corresponding authors: Miwa NAKANO, mwnakano@affrc.go.jpAbstractPlant diversity has been known to affect the produc-tivity and long-term stability of grassland ecosystem, as well as the mineral balance in grazing cattle. How-ever, there is little information on the relationship be-tween plant diversity and livestock productivity traits such as rumen digestion and fermentation. Rumen bacteria play an essential role in the fermentation and digestion of cattle diet. In microbiology, a highly di-verse microbial community is known to be able to re-spond quickly and ? exibly to environmental changes. In ? brous diets-fed cattle, the rumen bacterial diver-sity is found to be high diverse, as plant-based ? bers are rich in complex polysaccharides that enrich the microbial community. Based on the above informa-tion, we proposed the following hypothesis: complex fibrous composition of plants and high fiber intake by cattle in native pastures with greater plant species richness lead to high rumen bacterial diversity, which ensures stable fermentation and digestion, as well as flexibility toward rumen environmental changes. This year, we have investigated the rumen bacterial composition pro? le and rumen digestibility of cows grazing in two pastures with different plant species richness, using molecular biology techniques and in vitro incubation, respectively. Stability will be evalu-ated in terms of changes in bacterial composition and digestibility after a change in the feeding regime from pasture to barn. The authors believe that understand-ing the interaction between plant-species richness and livestock productivity will provide not only an evalu-ation of grassland ecosystem capability, but also the primary knowledge about the maintenance of stable rumen condition for livestock production.A grassland ecosystem with high plant diversity has been expected to have multiple functions in livestock production. Plant diversity has been known to affect the productivity and long-term stability of a grassland ecosystem (Tilman et al., 2006) as well as plant nutri-tional characteristics as a feed (Mizuno et al., 2014) and the mineral balance in grazing cattle (Mizuno et al., 2011). However, there is little information on the relationship between plant diversity and livestock productivity traits, such as rumen digestion and fer-mentation, which are important for livestock produc-tion. Microbes, especially bacteria, are essential in rumen function. Bacteria play an essential role in the fermentation of carbohydrates into volatile fatty ac-ids, the degradation of dietary protein, and the partial recapture of non-protein nitrogen as microbial cell protein for subsequent protein nutrition (Mohammed et al., 2014). Therefore, it is necessary to determine rumen bacterial composition as well as its interaction with plant diversity and rumen function—digestion and fermentation—in cattle to evaluate a grassland ecosystem with high plant diversity with respect to livestock production.A highly diverse microbial community is known to be able to respond quickly and flexibly to environmental changes (Miki, 2011). In rumen microbiology, the rumen bacterial diversity is found to be higher in forage-fed cattle than in high grain diet-fed cattle (Petri et al., 2013). Plant-based ? brous diets are rich in complex polysaccharides (e.g., cellulose and hemicellulose), lignin, and the other phenolic compounds. Fibrous feed particles composed of these compounds are colonized exclusively by closely adherent bacteria (Pitta et al., 2010). Some bacteria specialize in the transformation of plant lignin and the other phenolic compounds and in the formation of secondary substrates, such as cinnamic acid, which enhance polysaccharide hydrolysis by the other members of the biofilm (Larue et al., 2005). These 34Nakano and Oguraadherent bacteria are often associated with consortia of secondary bacterial colonizers (Pitta et al., 2010). Furthermore, thelong rumen retention time of ? brous diet facilitates the development of a more complex array of diet and intermediary substrates to support a more diverse bacterial community (Pitta et al., 2010). This information suggests that increases in the ? brous nature of the feed particles and the fiber intake of cattle result in greater diversity in the rumen bacterial population, leading to a stable rumen condition that responds quickly and ? exibly to rumen environmental changes.Generally, more plant species are observed in a native pasture compared to those in a sown pasture. Mizuno et al. (2012) reported that the number of plant species in pasture vegetation and herbage ingested by cows grazing on a native pasture was higher than that ingested by cows grazing on a sown pasture. The fibrous compound content of herbage ingested by cows grazing on a native pasture is also higher than that of herbage collected on a sown pasture (Nakano et al., 2007; NARO, 2009); seasonal changes in con-tents of crude protein and neutral detergent fiber of herbage ingested by cows grazing on a native pas-ture were relatively small (Nakano et al., 2015). The nutritional status (Nakano et al., 2015) and mineral balances (Mizuno et al., 2012) of cows grazing on a native pasture were relatively good, although scant dry matter and energy intake was detected in the fall (Nakano et al., 2015). Based on this information, we hypothesized that ingestion by cattle of a complex ? brous composition of plants owing to the foraging of many fibrous plant species along with the high ? ber intake in the native pasture with greater plant-species richness led to high rumen bacterial diversity. This ensures stable rumen function and productivity, ? exibility towards rumen environmental changes, and good nutritional status of cattle own.In preliminary research conducted at the Field Science Center, Graduate School of Agricultural Science, Tohoku University, Japan (38º 44’ N, 140º 15’ E, 300–600 m in elevation) in 2015, the rumen bacterial profiles of cows grazing on two native pastures with medium or high plant-species richness were compared using PCR-denaturing gradient gel electrophoresis (DGGE) of rumen bacterial 16S rRNA gene amplicons. Many bands were visually detected in the profiles of cows grazing on pasture with high plant-species richness compared with those grazing on pasture with medium plant-species richness (Fig. 1). This result suggested that the rumen bacterial population in cows grazing on a pasture with high plant-species richness might be more diverse and characteristic than that observed in cows grazing on a pasture with medium plant-species richness.The PCR-DGGE method used in this preliminary research allows the rapid screening of bacterial popu-lations and visualization of PCR products represent-ing predominant rumen bacterial communities (Hume et al., 2003). However, this method has to be used in combination with other analyses to identify the bacterial species and to de? ne a detailed population and community structure. Recently, some research-ers have studied rumen bacterial populations of cattle fed with high grain diet, high forage diet, silage, and fresh herbage by using next-generation sequencing approaches based on pyrosequencing (Pitta et al., 2010; Mohammed et al., 2014). Petri et al. (2013) de-termined the changes in rumen microbial populations as a result of acidotic inducing diets within individual animals, that have not been well elucidated by using DGGE method, by using 454-pyrosequencing. This approach enables us a new discovery through cost-effective sequence throughput in a relatively short time (Morozova and Marra, 2008). Furthermore, several studies have identified associations between particular rumen bacterial groups and fermentation products in cattle (Hernandez-Sanabria et al., 2010), indicating that the focus in the recent rumen bacterial studies have shifted from determining “who is there” (population) towards understanding “what are they doing” (their mechanisms of action) (Li et al., 2015). The focused correlations among microbial communi-ties in the rumen ecosystems of cattle (Kittelmann et al., 2013) and between bacterial communities and metabolic phenotypes of sika deer (Li et al., 2015) have been described visually by using co-occurrence network analysis. Co-occurrence network analysis is generally used to provide a graphic visualization of potential relationships between people, organiza-tions, concepts, or other entities represented within the available information (Yasuda, 1997). In rumen microbiology, this analysis is employed for under-standing the metabolic networks between rumen-inhabiting microbial groups and resolving their individual contributions to overall rumen functioning (Kittelmann et al., 2013). This approach may provide new clues about complex interactions among rumen 35Effect of Plant-species Richness on Microbial Composition and Rumen Functionbacterial diversity, rumen function, and its stability in cattle grazing on species-rich pastures.Using next generation sequencing and co-occurrence network analysis, the objectives of this study were to 1) investigate differences in the ? brous composi-tion of ingested herbage, rumen retention time, and bacterial composition of cattle grazing on pastures with high or low plant-species richness; 2) explore the associations among rumen bacterial diversity, ru-men function (rumen digestibility), and productivity (fermentation characteristics and amount of micro-bial protein synthesis); 3) explore the relationship between rumen bacterial diversity and stabilities of rumen digestion and fermentation; and 4) test the hypothesis that rumen bacterial diversity and rumen function and productivity are related to the plant-species richness in a pasture.The study has conducted from May 2016 at the Field Science Center, Graduate School of Agricultural Science, Tohoku University, Japan (38º 44’ N, 140º 15’ E, 300–600 m in elevation). The typical rumen bacterial composition pro? le and rumen digestibility of cows grazing in two pastures with high (native pasture) or low (sown pasture) plant-species rich-ness have been investigated using next-generation sequencing and in vitro incubation, respectively. Stability will be evaluated in terms of changes in bac-terial composition and digestibility after a change in the feeding regime from pasture to barn. The authors have collected rumen ? uid, urea, and blood samples from cows grazing on native and sown pastures, and has analyzed elements associated with rumen bacteri-al diversity, rumen fermentation, bacterial cell protein synthesis, and nutritional status. The authors hope to obtain interesting discoveries and discuss with you in other opportunities.Recently, in the dairy and beef production industry, rumen acidosis is increasingly recognized as a signi? -cant disorder. Rumen acidosis results from extreme fermentation due to feeding of high grain and low roughage diets. This extreme fermentation leads to an increase in acid and a decline in pH in the rumen, which alters the activity and abundance of many bac-terial species (Petri et al., 2013). Rumen fermentation and bacterial population during rumen acidosis have been extensively studied (Petri et al., 2013; Mao et al., 2013). Nevertheless, it is also necessary to reveal the stable rumen condition—bacterial composition and rumen function—that can adapt ? exibly toward these rapid changes in feed. An understanding of the interaction between plant-species richness and live-stock productivity would lead to an understanding of the factors responsible for stable rumen condition. The authors believe that understanding the interaction between plant-species richness and livestock produc-tivity will provide not only an evaluation of grassland ecosystem capability, but also primary knowledge about the maintenance of stable rumen condition for livestock production.  Fig. 1. Denaturing gradient gel electrophoresis (DGGE) pro? les of rumen bacterial 16S rRNA gene amplicons from cows grazing on two native pastures with medium or high plant-species richness in the preliminary research conducted in 2015. The image was normalized using the DGGE Marker II (Nippongenem Toyama, Japan) and Bio Numerics software, version 5.0 (Applied Maths, Austin, TS). Filled triangles (?) under the ? gure indicate the bands that were detected strongly or characteristically in pasture with high plant-species richness.36AcknowledgementThe authors are grateful to T. Shishido, T. Chiba, S. Takamizawa, Dr. A. Tozawa, R. Futahashi, N. Hatakeyama, QIANRIGE, Yin Liying (Tohoku Uni-versity), Dr. Y. Yamamoto, Dr. Y. Togamura, Dr. H. Ishizaki, and Dr. S. Haga (NARO, institute of Livestock and Grassland Science) for their useful suggestions and their technical assistance. This work was supported by JSPS KAKENHI Grant Number JP16K18789.ReferencesNational Agriculture and Food Research Organization (NARO)  (2009)  S tandard  t ab les  o f  f eed composition in Japan. Japan Livestock Industry Association, Tokyo, Japan. (in Japanese)Hernandez -Sanab r i a ,  E . ,  L .L .  Guan ,  L .A . Goonewardene, M. Li, D.F. Mujibi, P. Stothard, S.S. Moore and M.C. Leon-Quintero (2010) Correlation of particular bacterial PCR-denaturing gradient gel electrophoresis patterns with bovine ruminal fermentation parameters and feed efficiency traits. Appl Environ Microbiol, 76: 6338–6350.Hume, M.E., L.F. Kubena, T.S. Edrington, C.J. Donskey, R.W. Moore, S.C. Ricke and D.J. Nisbet (2003) Poultry digestive microflora biodiversity as indicated by denaturing gradient gel electrophoresis. 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Effect of Plant-species Richness on Microbial Composition and Rumen Function

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Effect of Plant-species Richness on Microbial Composition and Rumen Function

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