Biological models of the rumen function

Hobson, P. N.; Fonty, Gérard

doi:10.1007/978-94-009-1453-7_15

Cited by 10 publications

(12 citation statements)

References 42 publications

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“…In conventional lambs, a hydrogenotrophic acetogenic community became established rapidly after birth, as observed previously (61,62). In gnotoxenic lambs G1 and G2, inoculated acetogens established themselves quickly as the sole ruminal occupants, showing that, unlike the cellulolytic bacteria, which require a diverse microbiota for establishment (27,30,36), acetogens can colonize and become established independent of other microbes. Acetogens are metabolically very versatile, and heterotrophic growth is favored over autotrophic growth on H 2 -CO 2 (23,57).…”

Section: Discussionsupporting

confidence: 67%

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Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs

Fonty¹,

Joblin

Chavarot³

et al. 2007

Appl Environ Microbiol

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The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (10 7 to 10 8 cells g ؊1 ) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate-and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H 2 utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H 2 utilization was similar to that in conventional lambs. H 2 utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H 2 utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H 2 in the rumen.Methane (CH 4 ) eructated from ruminants represents a loss of 8 to 13% of the digestible energy ingested by the animal (71) and contributes to global warming. The amount of methane produced by ruminants varies with the farming system, the nature of the feed, the feeding level, the feed digestibility, and the animal species (6,67,71). The annual production of methane by ruminants, estimated to be 80 to 120 ϫ 10 6 tons or approximately 15% of total anthropogenic methane emissions (16,63), is the second largest biogenic source of methane after rice paddy fields. Decreasing methane emissions from ruminant livestock is desirable in order to both reduce greenhouse gases in the atmosphere and improve energy capture during digestion.Nutritionists have been trying for a long time to mitigate rumen methane emissions in order to enhance animal performance but so far have not been successful. The methods most commonly attempted involve utilization of antibiotics and ionophores (58), halogenated methane analogues (20,37,59), heavy metals (70), lipid-rich materials such as coconut oil (21,26,54,55,56), probiotics (58), bacteriocin (47), and numerous chemicals (1, 4). Immunization against methanogens (79), elimination of ciliate protozoans which support methanogen populations (64), and addition of acetogenic bacteria to rume...

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Section: Discussionsupporting

confidence: 67%

“…The use of gnotobiotically reared lambs harboring either a simple or complex microflora is an important method for investigating the role of specific microbes in the rumen (36). Such in vivo systems have already been used to study effects of methanogens in the rumen (33).…”

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confidence: 99%

Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs

Fonty¹,

Joblin

Chavarot³

et al. 2007

Appl Environ Microbiol

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“…Any changes to the structure and function of the rumen epithelium, including those triggered by SARA, may negatively impact the diversity and density of rumen fungi living there. Fungi have the slowest life cycles of rumen microorganisms (24–32 h) (Theodorou et al, 1996 ; Hobson and Fonty, 1997 ), and association with the rumen epithelium may help cells avoid wash-out. Fungi (Warner, 1966 ; Orpin, 1975 ; Gruninger et al, 2014 ) and protozoa (Hook et al, 2012 ; Williams and Coleman, 2012 ) are known to associate with rumen epithelial cells until chemotaxis draws them into the liquid and solid fractions.…”

Section: Discussionmentioning

confidence: 99%

An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation

Ishaq¹,

AlZahal

Walker

et al. 2017

Front. Microbiol.

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Sub-acute ruminal acidosis (SARA) is a gastrointestinal functional disorder in livestock characterized by low rumen pH, which reduces rumen function, microbial diversity, host performance, and host immune function. Dietary management is used to prevent SARA, often with yeast supplementation as a pH buffer. Almost nothing is known about the effect of SARA or yeast supplementation on ruminal protozoal and fungal diversity, despite their roles in fiber degradation. Dairy cows were switched from a high-fiber to high-grain diet abruptly to induce SARA, with and without active dry yeast (ADY, Saccharomyces cerevisiae) supplementation, and sampled from the rumen fluid, solids, and epimural fractions to determine microbial diversity using the protozoal 18S rRNA and the fungal ITS1 genes via Illumina MiSeq sequencing. Diet-induced SARA dramatically increased the number and abundance of rare fungal taxa, even in fluid fractions where total reads were very low, and reduced protozoal diversity. SARA selected for more lactic-acid utilizing taxa, and fewer fiber-degrading taxa. ADY treatment increased fungal richness (OTUs) but not diversity (Inverse Simpson, Shannon), but increased protozoal richness and diversity in some fractions. ADY treatment itself significantly (P < 0.05) affected the abundance of numerous fungal genera as seen in the high-fiber diet: Lewia, Neocallimastix, and Phoma were increased, while Alternaria, Candida Orpinomyces, and Piromyces spp. were decreased. Likewise, for protozoa, ADY itself increased Isotricha intestinalis but decreased Entodinium furca spp. Multivariate analyses showed diet type was most significant in driving diversity, followed by yeast treatment, for AMOVA, ANOSIM, and weighted UniFrac. Diet, ADY, and location were all significant factors for fungi (PERMANOVA, P = 0.0001, P = 0.0452, P = 0.0068, Monte Carlo correction, respectively, and location was a significant factor (P = 0.001, Monte Carlo correction) for protozoa. Diet-induced SARA shifts diversity of rumen fungi and protozoa and selects against fiber-degrading species. Supplementation with ADY mitigated this reduction in protozoa, presumptively by triggering microbial diversity shifts (as seen even in the high-fiber diet) that resulted in pH stabilization. ADY did not recover the initial community structure that was seen in pre-SARA conditions.

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“…Neonatal ruminants undergo rumen development over a period of 8–12 weeks, during which the rumen and reticulum increase in size and functionality [ 10 ]. This process is enhanced by microbial colonization of the rumen and the introduction of a fiber-based diet [ 11 – 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…Rumen development in young animals can be further improved using probiotics [ 10 , 20 , 21 ]. Probiotics for livestock are generally comprised of LAB or fibrolytic bacteria.…”

Section: Introductionmentioning

confidence: 99%

Fibrolytic Bacteria Isolated from the Rumen of North American Moose (Alces alces) and Their Use as a Probiotic in Neonatal Lambs

Ishaq¹,

Kim²,

Reis³

et al. 2015

PLoS ONE

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Fibrolytic bacteria were isolated from the rumen of North American moose (Alces alces), which eat a high-fiber diet of woody browse. It was hypothesized that fibrolytic bacteria isolated from the moose rumen could be used as probiotics to improve fiber degradation and animal production. Thirty-one isolates (Bacillus, n = 26; Paenibacillus, n = 1; and Staphylococcus, n = 4) were cultured from moose rumen digesta samples collected in Vermont. Using Sanger sequencing of the 16S rRNA gene, culturing techniques, and optical densities, isolates were identified and screened for biochemical properties important to plant carbohydrate degradation. Five isolates were selected as candidates for use as a probiotic, which was administered daily to neonate lambs for 9 weeks. It was hypothesized that regular administration of a probiotic to improve fibrolysis to neonate animals through weaning would increase the developing rumen bacterial diversity, increase animal production, and allow for long-term colonization of the probiotic species. Neither weight gain nor wool quality was improved in lambs given a probiotic, however, dietary efficiency was increased as evidenced by the reduced feed intake (and rearing costs) without a loss to weight gain. Experimental lambs had a lower acetate to propionate ratio than control lambs, which was previously shown to indicate increased dietary efficiency. Fibrolytic bacteria made up the majority of sequences, mainly Prevotella, Butyrivibrio, and Ruminococcus. While protozoal densities increased over time and were stable, methanogen densities varied greatly in the first six months of life for lambs. This is likely due to the changing diet and bacterial populations in the developing rumen.

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Biological models of the rumen function

Cited by 10 publications

References 42 publications

Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs

Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs

An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation

Fibrolytic Bacteria Isolated from the Rumen of North American Moose (Alces alces) and Their Use as a Probiotic in Neonatal Lambs

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