Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

2004 - 200912020 - 20221

Settings

Subject: search.filters.subject.Ruminant

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    MECHANISMS CONTROLLING VOLATILE FATTY ACID AND FERMENTATION GAS PRODUCTION IN THE RUMEN
    (2022) Scott, Jarvis G; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Atmospheric methane accounts for less than approximately 16% of global anthropogenic greenhouse gas emission. However, it is significantly greater and trapping heat when compared to atmospheric CO2 on a molar lever and any reduction in atmospheric abundance in warranted. Enteric methane from ruminant species accounts for a fraction (< 30%) of the total atmospheric methane however its production also accounts for major dietary energy loss in ruminant species and affects feed efficiency and overall production. Major studies have investigated numerous feed additives and supplements with highly variable finding on the antimethanogenic property of these compounds or feeding strategies, however the findings have raised other questions regarding shifts in VFA profiles accompanying methane inhibition. Higher inclusion levels of concentrate and other nonstructural starch in the diet of ruminants have been shown to decrease methane production and shift volatile fatty acid (VFA) profiles in the rumen. Additionally, many studies have suggested that inhibiting methane production avails as a reducing equivalent to fuel the propionate producing pathway and therefore results in shift in VFA profiles in the rumen. However, very little is understood regarding how these VFA shifts come about. Microbial Kinetics and thermodynamics are physiochemical principles that can be used to study how concentrate inclusion in ruminant diets can change the substrate concentrations and ultimately lead to shifts in fermentation profile in the rumen. Substrate availability supports and/or limits the growth of microbial population in the rumen, while the accumulation of the products or reactants for major fermentation reactions dictate the profile of the VFA. Understanding the role of these physiochemical principles and ultimately the mechanisms involved with changes the profile of VFA and fermentations gas in the rumen would help researchers understand how VFA profiles are shifting during methane inhibition as well as possibly identifying a more targeted approach for inhibiting enteric methane production. Therefore, the objectives of this projects are: to develop an in vitro method to understand the basal kinetic parameters of metabolism in the rumen, to evaluate the effects of increasing forage-to-concentrate ratio on performance and change in in VFA and fermentation gas in vivo, and to test the effect of various perturbations (fermentation metabolites e.g. sodium acetate, sodium lactate etc.) on the fermentation profile of rumen fluid adjusted to different forage-to-concentrate ration. The results indicate that rumen fluid from cows on a high-concentrate diet have a greater capacity to make propionate compared to the high forages diet. The higher propionate production limits the availability of which is necessary for the synthesis of CH4. The finding also suggests that methanogenesis is process limited by substrate concentration. Finally, our studies indicate that feeding strategies targeting enzymatic activity favoring propionate production may be more beneficial than targeting methanogens in a high forage diet.
  • Thumbnail Image
    Item
    Regulation of Urea Recycling into the Gastrointestinal Tract and Ammonia Metabolism in Ruminants
    (2004-12-08) Sunny, Nishanth Edakulathur; Bequette, Brian J; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The primary objective of this study was to determine the extent ruminants control urea recycling to the gastrointestinal tract (GIT), independent of rumen microbial metabolism. Urea kinetics were determined by continuous infusion of [15N15N]urea (4 levels) to jugular vein of sheep (n = 4; 28.1kg) fed a low protein (6.8%) diet. Although urea recycling to the GIT (P < 0.001) increased with each level of urea, the proportion (P < 0.001) and amount (P < 0.001) of recycled urea returning as ammonia to liver for ureagenesis also increased. In consequence a decreasing proportion (P = 0.003) of recycled urea was used for microbial protein synthesis. The present study suggests that ruminants have a large capacity to partition urea-N to the GIT. Thus, rather than up-regulating urea recycling, there appears to be more potential to improve N efficiency in ruminants by manipulating the rumen environment to optimize capture of recycled N.