Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrence patterns between microbes, suggesting that major metabolic interactions are non-selective rather than specific.

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Rumen microbial community composition varies with diet and host, but a core microbiome is found across a wide geographical range

Stevens, C. Edward, and Ian D. Hume. Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients. Physiol. Rev. 78: 393–427, 1998. — The vertebrate ga...

Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients

1. The Digestive System of the Rabbit 2. Digestion of Starch and Sugars 3. Protein Digestion 4. Fat Digestion 5. Fibre Digestion 6. Energy and Protein Metabolism 7. Minerals, Vitamins and Additives 8. Feed Evaluation 9. Influence of the Diet on Rabbit Meat Quality 10. Nutrition and Pathology 11. Feed Manufacturing 12. Feed Formulation 13. Feeding Behaviour of the Rabbit 14. Feeding Systems for Intensive Production 15. Nutrition and Climatic Environment 16. Nutritional Recommendations and Feeding Management of Angora Rabbits 17. Pet Rabbit Feeding and Nutrition.

Nutrition of the rabbit

http://www.rabway.com/_wiki/images/archive/2/2d/20130916124647!Nutrition_of_the_Rabbit.pdf

The Nutrition of the Rabbit

The carbon-isotope composition of hair and feces offers a glimpse into the diets of mammalian herbivores. It is particularly useful for determining the relative consumption of browse and graze in tropical environments, as these foods have strongly divergent carbon-isotope compositions. Fecal δ 13 C values reflect the last few days consumption, whereas hair provides longer term dietary information. Previous studies have shown, however, that some fractionation occurs between dietary δ 13 C values and those of hair and feces. Accurate dietary reconstruction requires an understand- ing of these fractionations, but few controlled-feeding studies have been undertaken to investigate these fractionations in any mammalian taxa, fewer still in large mammalian herbivores. Here, we present data from the first study of carbon-isotope fractionation between diet, hair, and feces in multiple herbivore taxa. All taxa were fed pure alfalfa (Medicago sativa) diets for a minimum period of 6 months, at which point recently grown hair was shaved and ana- lyzed for carbon isotopes. The mean observed diet-hair fractionation was +3.2‰, with a range of +2.7 to +3.5‰. We also examined diet-feces fractionation for herbivores on alfalfa and bermudagrass (Cynodon dactylon) feeds. The mean diet-feces fractionation for both diets was -0.8‰, with less fractionation for alfalfa (-0.6‰) than bermudagrass (-1.0‰). Fecal carbon turnover also varies greatly between taxa. When diets were switched, horse (Equus caballus) feces reflected the new diet within 60 h, but alpaca (Lama pacos) feces did not equilibrate with the new diet for nearly 200 h. Thus, fecal carbon isotopes provide far greater dietary resolution for hindgut-fermenting horses than foregut-fermenting alpacas.

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An experimental study of carbon-isotope fractionation between diet, hair, and feces of mammalian herbivores

1. Digesta passage and retention were measured in heifers, sheep, goats, equines and rabbits of varying body-weights when given timothy (Phleum pratense) hay. 2. Two passage markers were compared, cobalt (III) ethylene diamine tetraacetate (CoEDTA) and chromiummordanted timothy fibre for liquid and solid phase respectively. Both markers were injected into the rumen of the ruminants and into the caecum of the equines and rabbits. 3. In ruminants, two different sets of rate constants (k1 and k2) were derived from a two-pool model for marker passage, using a graphical approach and a computer-based non-linear least-squares curve-fitting technique. 4. Retention times, due to unidirectional flow through the gastrointestinal tract (transit time) and due to pool effects (mean retention time, MRT), were calculated. 5. Curve fitting was only successful for the excretion of liquids in ruminants. The two-pool model was not applicable to the passage of solids. 6. Apparent retention of liquid was always shorter than for solids in all species, except in rabbits. However, absorption of CoEDTA was too large in the rabbits to determine liquid retention accurately. Times for first appearance of the two markers were similar within animal groups. 7. MRT values were lowest in the rabbit, intermediate in equines and high in the ruminants. The MRT values (h) of solids and liquids respectively were: large heifers 65, 18; small heifers 48, 20; goats 41, 28; sheep 57, 26; equines 23, 18; rabbits 5.3, not determined. 8. Liquid retention seemed to decrease somewhat with increasing body-weight in the ruminants. Solids retention decreased with decreasing body-weight in the ruminants, but sheep had longer retention times than goats of similar size. Equines exhibited large individual variation in retention of the liquid or solid markers, seemingly unrelated to size. No effect of size was seen in the retention of solids in the rabbits.

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T. R. Rounsaville

Papers

The measurement of liquid and solid digesta retention in ruminants, equines and rabbits given timothy (Phleum pratense) hay.