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R G Megarrity

Bio: R G Megarrity is an academic researcher from Commonwealth Scientific and Industrial Research Organisation. The author has contributed to research in topics: Leucaena & Leucaena leucocephala. The author has an hindex of 1, co-authored 1 publications receiving 210 citations.

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TL;DR: In the absence of any disease in the animals, clearance has been given for the wider use of these cultures in areas where Leucaena is grown, and limited evidence suggests that the leucaena toxicity problem can be solved by the use ofThese introduced bacteria.
Abstract: Cattle and goats in Australia lack the ability to totally degrade 3-hydroxy-4(1H)-pyridone, also known as 3,4-dihydroxy pyridine (3,4 DHP), the ruminal metabolite of mimosine, a toxic aminoacid present in the leguminous shrub Leucaena leucocephala. Ruminants in Hawaii have this capacity due to the presence of micro-organisms able to rapidly degrade the DHP. A mixed bacterial population capable of rapidly degrading DHP in vitro was isolated from a goat on the island of Maui. Cultures were grown anaerobically, without added sugars, in Medium 98-5 containing DHP. Cultures at a dilution of 10(-12) from the original rumen fluid were introduced into Townsville and further sub-cultured and multiplied in vitro in strict isolation at the Oonoonba Veterinary Laboratory, Townsville. Infusion of the culture into a goat and a steer fed a 100% leucaena diet resulted in cessation of DHP excretion in the urine. After 60 days the serum thyroxine levels and thyroid size were normal and there were no clinical signs of disease. The ability of the rumen fluid to degrade DHP in vitro showed that the bacteria had become established in the rumen. In the absence of any disease in the animals, clearance has been given for the wider use of these cultures in areas where leucaena is grown. The limited evidence suggests that the leucaena toxicity problem can be solved by the use of these introduced bacteria.

223 citations


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TL;DR: The necessity to use molecular biology techniques for identification and characterization of rumen microbes has been emphasized in this review and the microbial ecosystem is well studied for the rumen of domesticated animals, but it is poorly studied in buffalo and wild ruminants.
Abstract: The inhabitants of the rumen microbial eco-system, a complex consortium of different microbial groups living in symbiotic relationship with the host, act synergistically for the bioconversion of lignocellulosic feeds intovolatile fatty acids which serve as a source of energy for the animals. The constraints, imposed by the host and the feed consumed by the animal, under which these microbes have to function, have been discussed. The eco-system is specialized and buffered in a narrow range of pH, which helps the animal to maintain a very well stabilized eco-system which is not disturbed by the incoming microbial contaminants into the fermentation sac (rumen) through feed and water intake. The microbial ecosystem is well studied for the rumen of domesticated animals like cattle, sheep and goat, but it is poorly studied in buffalo and wild ruminants. The necessity to use molecular biology techniques for identification and characterization of rumen microbes has been emphasized in this review.

595 citations

01 Jan 2013
TL;DR: In this article, the potential of nutritional, manure and animal husbandry practices for mitigating methane (CH4) and nitrous oxide (N2O) emissions from livestock production was evaluated.
Abstract: Animal production is a significant source of greenhouse gas (GHG) emissions worldwide. Depending on the accounting approaches and scope of emissions covered, estimates by various sources (IPCC, FAO, EPA or others) place livestock contribution to global anthropogenic GHG emissions at between 7 and 18 percent. The current analysis was conducted to evaluate the potential of nutritional, manure and animal husbandry practices for mitigating methane (CH4) and nitrous oxide (N2O) – i.e. non-carbon dioxide (non-CO2) – GHG emissions from livestock production. These practices were categorized into enteric CH4, manure management and animal husbandry mitigation practices. Emphasis was placed on enteric CH4 mitigation practices for ruminant animals (only in vivo studies were considered) and manure mitigation practices for both ruminant and monogastric species. Over 900 references were reviewed; and simulation and life cycle assessment analyses were generally excluded. In evaluating mitigation practices, the use of proper units is critical. Expressing enteric CH4 energy production on gross energy intake basis, for example, does not accurately reflect the potential impact of diet quality and composition. Therefore, it is noted that GHG emissions should be expressed on a digestible energy intake basis or per unit of animal product (i.e. GHG emission intensity), because this reflects most accurately the effect of a given mitigation practice on feed intake and the efficiency of animal production. EntErIC CH4 MItIgAtIon prACtICEs Increasing forage digestibility and digestible forage intake will generally reduce GHG emissions from rumen fermentation (and stored manure), when scaled per unit of animal product, and are highly-recommended mitigation practices. For example, enteric CH4 emissions may be reduced when corn silage replaces grass silage in the diet. Legume silages may also have an advantage over grass silage due to their lower fibre content and the additional benefit of replacing inorganic nitrogen fertilizer. Effective silage preservation will improve forage quality on the farm and reduce GHG emission intensity. Introduction of legumes into grass pastures in warm climate regions may offer a mitigation opportunity, although more research is needed to address the associated agronomic challenges and comparative N2O emissions with equivalent production levels from nitrogen fertilizer. Dietary lipids are effective in reducing enteric CH4 emissions, but the applicability of this practice will depend on its cost and its effects on feed intake, production and milk composition. High-oil by-product feeds, such as distiller’s grains, may offer an economically feasible alternative to oil supplementation as a mitigation practice, although their higher fibre content may have an opposite effect on enteric CH4, depending on basal diet composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease enteric CH4 emissions per unit of animal product, particularly when above 40 percent of dry matter intake. The effect may depend on type of ‘concentrate’ inclusion rate, production response, impact on fibre digestibility, level of nutrition, composition of the basal diet and feed processing.

316 citations

Journal ArticleDOI
TL;DR: The ruminal microbial community is remarkably diverse, containing 100s of different bacterial and archaeal species, plus many species of fungi and protozoa, including a “core microbiome” dominated by phyla Firmicutes and Bacteroidetes, but also containing many other taxa.
Abstract: 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.

309 citations

Journal ArticleDOI
TL;DR: Paper presented at the "Symposium on Ingestion of Poisonous Plants by Livestock," February 15, 1990, Reno, Nevada.
Abstract: Paper presented at the "Symposium on Ingestion of Poisonous Plants by Livestock," February 15, 1990, Reno, Nevada.

257 citations

Journal ArticleDOI
TL;DR: Analysis of published data on animal management practices that mitigate enteric methane (CH4) and nitrous oxide (N2O) emissions from animal operations found that pursuing a suite of intensive and extensive reproductive management technologies provides a significant opportunity to reduce GHG emissions.
Abstract: The goal of this review was to analyze published data on animal management practices that mitigate enteric methane (CH4) and nitrous oxide (N2O) emissions from animal operations. Increasing animal productivity can be a very effective strategy for reducing greenhouse gas (GHG) emissions per unit of livestock product. Improving the genetic potential of animals through planned cross-breeding or selection within breeds and achieving this genetic potential through proper nutrition and improvements in reproductive efficiency, animal health, and reproductive lifespan are effective approaches for improving animal productivity and reducing GHG emission intensity. In subsistence production systems, reduction of herd size would increase feed availability and productivity of individual animals and the total herd, thus lowering CH4 emission intensity. In these systems, improving the nutritive value of low-quality feeds for ruminant diets can have a considerable benefit on herd productivity while keeping the herd CH4 output constant or even decreasing it. Residual feed intake may be a tool for screening animals that are low CH4 emitters, but there is currently insufficient evidence that low residual feed intake animals have a lower CH4 yield per unit of feed intake or animal product. Reducing age at slaughter of finished cattle and the number of days that animals are on feed in the feedlot can significantly reduce GHG emissions in beef and other meat animal production systems. Improved animal health and reduced mortality and morbidity are expected to increase herd productivity and reduce GHG emission intensity in all livestock production systems. Pursuing a suite of intensive and extensive reproductive management technologies provides a significant opportunity to reduce GHG emissions. Recommended approaches will differ by region and species but should target increasing conception rates in dairy, beef, and buffalo, increasing fecundity in swine and small ruminants, and reducing embryo wastage in all species. Interactions among individual components of livestock production systems are complex but must be considered when recommending GHG mitigation practices.

250 citations