The ruminal microbial community is remarkably diverse, containing hundreds of different bacterial and archaeal species, plus many species of fungi and protozoa. Molecular studies have identified a “core microbiome” dominated by phyla Firmicutes and Bacteroidetes, but also containing many other taxa. The rumen provides an ideal laboratory for studies on microbial ecology and the demonstration of ecological principles. In particular, the microbial community demonstrates both redundancy (overlap of function among multiple species) and resilience (resistance to, and capacity to recover from, perturbation). These twin properties provide remarkable stability that maintains digestive function for the host across a range of feeding and management conditions, but they also provide a challenge to engineering the rumen for improved function (e.g., improved fiber utilization or decreased methane production). Direct ruminal dosing or feeding of probiotic strains often fails to establish the added strains, due to intensive competition and amensalism from the indigenous residents that are well-adapted to the historical conditions within each rumen. Known exceptions include introduced strains that can fill otherwise unoccupied niches, as in the case of specialist bacteria that degrade phytotoxins such as mimosine or fluoroacetate. An additional complicating factor in manipulating the ruminal fermentation is the individuality or host specificity of the microbiota, in which individual animals contain a particular community whose species composition is capable of reconstituting itself, even following a near-total exchange of ruminal contents from another herd mate maintained on the same diet. Elucidation of the interactions between the microbial community and the individual host that establish and maintain this specificity may provide insights into why individual hosts vary in production metrics (e.g., feed efficiency or milk fat synthesis), and how to improve herd performance.

/pdf/redundancy-resilience-and-host-specificity-of-the-ruminal-27alixfpjt.pdf

Redundancy, resilience, and host specificity of the ruminal microbiota: implications for engineering improved ruminal fermentations.

Two experiments were conducted to evaluate the effects of increasing concentrations of glycerol in concentrate diets on total tract digestibility, methane (CH4) emissions, growth, fatty acid profiles, and carcass traits of lambs In both experiments, the control diet contained 57% barley grain, 145% wheat dried distillers grain with solubles (WDDGS), 13% sunflower hulls, 65% beet pulp, 63% alfalfa, and 3% mineral-vitamin mix Increasing concentrations (7, 14, and 21% dietary DM) of glycerol in the dietary DM were replaced for barley grain As glycerol was added, alfalfa meal and WDDGS were increased to maintain similar concentrations of CP and NDF among diets In Exp1, nutrient digestibility and CH4 emissions from 12 ram lambs were measured in a replicated 4 × 4 Latin square experiment In Exp 2, lamb performance was evaluated in 60 weaned lambs that were blocked by BW and randomly assigned to 1 of the 4 dietary treatments and fed to slaughter weight In Exp 1, nutrient digestibility and CH4 emissions were not altered (P = 015) by inclusion of glycerol in the diets In Exp2, increasing glycerol in the diet linearly decreased DMI (P < 001) and tended (P = 006) to reduce ADG, resulting in a linearly decreased final BW Feed efficiency was not affected by glycerol inclusion in the diets Carcass traits and total SFA or total MUFA proportions of subcutaneous fat were not affected (P = 077) by inclusion of glycerol, but PUFA were linearly decreased (P < 001) Proportions of 16:0, 10t-18:1, linoleic acid (18:2 n-6) and the n-6/n-3 ratio were linearly reduced (P < 001) and those of 18:0 (stearic acid), 9c-18:1 (oleic acid), linearly increased (P < 001) by glycerol When included up to 21% of diet DM, glycerol did not affect nutrient digestibility or CH4 emissions of lambs fed barley based finishing diets Glycerol may improve backfat fatty acid profiles by increasing 18:0 and 9c-18:1 and reducing 10t-18:1 and the n-6/n-3 ratio

Effects of increasing concentrations of glycerol in concentrate diets on nutrient digestibility, methane emissions, growth, fatty acid profiles, and carcass traits of lambs.

Globally, methane emissions account for 40–45% of greenhouse gas emissions from ruminant livestock, with over 90% of these emissions arising from enteric fermentation. Consequently, enteric CH4 emi...

Strategies to reduce greenhouse gases from ruminant livestock

This experiment was conducted to evaluate the effects of increasing concentrations of crude glycerin (CGLY) in diets on nutrient utilization, ruminal fermentation characteristics, and nitrogen utilization of goats. Four male crossbred (Thai Native×Anglo Nubian) goats, with an average initial weight of 26±3.0 kg, were randomly assigned according to a 4×4 Latin square design with four 21 days consecutive periods. Treatments diets contained 0%, 5%, 10%, and 20% of dietary DM of CGLY. Based on this experiment, there were no significant differences (p>0.05) among treatment groups regarding DM intake and digestion coefficients of nutrients (DM, OM, CP, EE, NDF, and ADF). Likewise, mean serum glucose, BHBA, and PCV concentrations were not affected (p>0.05) by dietary treatments, whereas serum insulin concentration linearly increased (L, p = 0.002) with increasing the amount of CGLY supplementation. Ruminal pH, NH3-N, and BUN concentration were unchanged by dietary treatments, except for 20% of CGLY, NH3-N, and BUN were lower (p<0.05) than for the diets 10% of CGLY, while the difference between the diets 0%, 5%, and 20% of CGLY were not significant. The amount of N absorption and retention were similar among treatments. Based on this study, CGLY levels up to 20% in total mixed ration could be efficiently utilized for goats and this study elucidates a good approach to exploiting the use of biodiesel production for goat production.

/pdf/effects-of-dietary-crude-glycerin-supplementation-on-gcvmaiwpo9.pdf

Effects of Dietary Crude Glycerin Supplementation on Nutrient Digestibility, Ruminal Fermentation, Blood Metabolites, and Nitrogen Balance of Goats

Effects on enteric methane production and bacterial and archaeal communities by the addition of cashew nut shell extract or glycerol-an in vitro evaluation.

Young-Bae Cho

Papers

Glycerol as a feed supplement for ruminants: In vitro fermentation characteristics and methane production