Effects of Oxygenated Drinking Water on Gaseous Emissions, Rumen Microorganisms, and Milk Production in Dairy Cattle

Since the beginning of the industrial revolution, concentrations of greenhouse gases (GHG) in the atmosphere have increased due to anthropogenic activities, which are believed to have led to an increase in global temperature. Anthropogenic GHG production originates primarily from the burning of fossil fuels; however, there are a variety of other sectors producing GHG that deserve attention as major sources. One such industry central to the success and growth of civilization is agriculture. While there is potential and need for a reduction in GHG emissions from plant agricultural systems, the present thesis will focus on animal agriculture. Animal agricultural systems, primarily ruminant production systems, produce the majority of GHG from the agricultural sector. There is a great need to research and implement production strategies that will reduce GHG emissions from a variety of ruminant animal production settings.;The present thesis introduces the topic of global warming with a review of current climate change statistics, global warming potential of various GHG, and sources of GHG from dairy cattle production systems. The literature review further focuses on enteric methane production from ruminant animals, including the source of methane production in the stomach of ruminant animals, techniques utilized in the measurement of enteric gaseous emissions, as well as the major methane mitigation techniques currently established for ruminants. Pilot studies and an original research project were conducted using dairy cattle as the ruminant model of choice.;Dairy cattle production systems contribute to GHG emissions, predominantly in the form of methane. Enteric methane is formed by methanogenic archaea (methanogens) that require strict anaerobic conditions to grow. A water treatment system was used to increase the dissolved oxygen concentration in drinking water. We hypothesized that increasing the dissolved oxygen concentration of the rumen through intake of oxygenated drinking water would create an environment detrimental to the proliferation of obligate anaerobic methanogens. This study evaluated carbonaceous and nitrogenous gaseous emissions in addition to performance parameters. A total of 36 lactating Holstein dairy cows were used in a completely randomized design. The cows were assigned to two treatment groups: control water and oxygenated drinking water (CON and OXI, respectively). The cows were housed in 3 groups of 6 animals within each treatment (n = 3). Dry matter intake (DMI), water intake (WI), and milk yield (MY) were recorded daily. Rumen fluid samples were extracted via an orogastric tube and quantified for bacteria, methanogens, and protozoa. Cows were placed inside an environmental chamber to measure carbon dioxide, nitrous oxide, and ammonia using the Innova 1412 photoacoustic field gas monitor (California Analytical Instruments, Orange, CA) and methane using the TEI 55C direct methane analyzer (Thermo Environmental Instruments, Franklin, MA). All measurements were analyzed using Proc Mixed in SAS. The DMI, WI, and energy corrected milk yield were similar but OXI versus CON treated cattle had reduced MY (P<0.05). Bacteria, methanogen, and protozoa quantification yielded no differences between treatments. While methane production was similar between treatments, ammonia emissions were higher for OXI cattle (P<0.05). Introduction of oxygen to the rumen via drinking water did not produce the anticipated effect on methane reduction but instead resulted in changes in nitrogen metabolism.