Master of Science, The Ohio State University, 2017, Animal Sciences

This research was designed to study the long-term effects of feeding a high corn reduced-fat distillers grains (RFDG) on long-term performance, and nutrient excretion and utilization of dairy cattle and if the addition of monensin to a high-RFDG diet affected performance and nutrient excretion. To assess these objectives, 36 mid-lactation Holstein cows were fed either a control (CON), a 28.8% RFDG diet (DM basis) replacing SBM, soyhulls, and supplemental fat and calcium phosphate (DG), or the DG diet with monensin at 20 mg/kg of DM (DGMon). The experiment was conducted for 11 weeks during which dry matter intake (DMI); milk yield, composition, and fatty acid profile; fecal, and urinary excretion and milk secretion of nitrogen (N), phosphorus (P) and sulfur (S) were measured. For the production portion of the experiment, RFDG diets (i.e., DG + DGMon) vs. CON did not affect milk yield (40.3 vs. 40.8 kg/d), but decreased DMI (24.9 vs. 26.4 kg/d), milk fat yield (1.12 vs.1.55 kg/d), milk protein yield (1.24 vs. 1.32 kg/d), and energy-corrected milk yield (37.7 vs. 43.5 kg/d). Adding monensin to the DG diet (i.e., DGMon vs. DG) did not affect DMI (24.4 vs. 25.4 kg/d) and milk yield (39.2 vs. 41.3 kg/d), but decreased milk fat yield (1.08 vs. 1.23 kg/d), milk protein yield (1.20 vs. 1.28 kg/d), and energy-corrected milk yield (36.0 vs. 39.4 kg/d). Additionally, difference in DMI between treatments increased as the experiment progressed and tended to be different by the conclusion of the trial (27.8, 25.4, and 23.4 kg/d for CON, DG and DGMon, respectively). Furthermore, milk fat yield and energy-corrected milk yield decreased for DG diets vs. CON as the experiment progressed. For milk fatty acid profile, feeding DG and DGMon compared to CON resulted in an increased concentration of trans-10, cis-12 18:2, trans-10 18:2, long-chain (> 16C), and polyunsaturated fatty acids, and a decrease in short-chain (<16C) and most odd- and branched-chain fatty acids compared with CON (open full item for complete abstract)

Committee: Chanhee Lee (Advisor); William Weiss (Committee Member); Thaddeus Ezeji (Committee Member) Subjects: Animal Sciences

Doctor of Philosophy, The Ohio State University, 2006, Evolution, Ecology, and Organismal Biology

Lake Erie is facing many perturbations. This study focuses on two issues, the external phosphorus loading and dreissenids' invasion, and investigates the interactions of the responses of the lower trophic levels to these two stressors. I construct an ecological model, EcoLE, based on a USEPA two-dimensional hydrodynamic and water quality model, CE-QUAL-W2. Data from the field year 1997 are used to calibrate the model, while data from 1998 and 1999 are used for verification. There is a good agreement between the modeled and field-measured state variables, and EcoLE catches the major characteristics of the physical, chemical and biological processes found in Lake Erie. We are confident in using this model for qualitative analysis, but one should be cautious in using it for quantitative predictions of Lake Erie processes. When I turn off the turbulent mixing processes, total dissolved phosphorus (TP-F) becomes concentrated in the lower water strata and diatom biomass decreases dramatically. When I turn on the mixing processes again, there is more TP-F in the upper water strata but less TP-F accumulated in the whole water column, because non-diatom edible algae (NDEA) and diatoms become more abundant in the water column. Blue-green algae are less affected by hydrodynamics but depend on the amount of available phosphorus in the whole water column. When I turn off the chemical and biological processes, external TP loads are distributed throughout the western basin and the west central basin as a result of physical mixing. External TP loads have minor direct effects on the east central and the eastern basins, where up to 60% of the daily algal P-demands come from SRP released by organic matter decomposition and by algal and crustacean P excretion. Dreissenid mussel daily grazing impact is less than 10% of the NDEA and diatom biomass in the western basin, and only 1-2% in the central and eastern basins. Impacts of dreissenid nutrient excretion become more important than the (open full item for complete abstract)

Committee: David Culver (Advisor) Subjects: Biology, Limnology

Master of Science, Miami University, 2003, Zoology

Fish are important in coupling benthic and pelagic habitats by consuming benthic prey and providing essential nutrients (nitrogen N and phosphorus P) to algae. However, because a complete understanding of fish effects on nutrient dynamics is still lacking, I measured how fish excretion rates (N and P) are affected by variable consumption rates under laboratory and field conditions. Then measured the effects changes in excretion rates had on community and nutrient dynamics. Results showed that variable consumption rates can alter fish excretion rates of nutrients and that algal biomass and sedimentation increased when fish fed on benthic prey, compared to fish not fed benthic prey. Thus, providing experimental evidence that benthic-pelagic coupling, via fish induced translocation and sedimentation shapes pelagic food-webs and cycling of nutrients between pelagic and benthic habitats. Lastly, fish body and excreted N:P both increased with consumption rate, suggesting that stoichiometry models need to better incorporate consumption rate.

Committee: Mike Vanni (Advisor) Subjects: Biology, Zoology