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The objective of this dissertation is to integrate information from a nonlinear ration formulation model, a thermal balance model, and emission and excretion models to evaluate the environment impact of dairy cattle and the effect of climate on dairy cattle at the farm level. The first chapter investigated the application of iterative linear programming (iteLP), sequential quadratic programming (SQP) and mixed-integer nonlinear programming based deterministic global optimization (MINLP_DGO) on designing feed formulation for dairy cattle based on NRC (2001). A simulation study showed that iteLP had limited capability to design least cost diets when nonlinearity existed in the constraints. Both SQP and MINLP_DGO were able to handle nonlinear constraints well, with SQP being faster but MINLP_DGO being more reliable. In the second chapter, a thermal balance model was developed to predict the body temperature and heat fluxes for Holstein dairy cattle under heat stress conditions. The model included five nodes representing the body core, skin and coat of a dairy cow. Heat production by the animal, heat conduction through the body core, skin and coat, and heat flows between the animal and the environment, including conduction, convection, evaporation and radiation, were calculated based on existing models and physical principles. Model evaluation suggested a likely overestimation of body temperature. Sensitivity analysis showed that heat production, surface area, air pressure and the parameters relative to respiration and sweating were the most sensitive. In the third chapter, environmental impact of dairy cattle was evaluated by considering relevant outputs simultaneously. Three multivariate Bayesian regression models were developed to predict enteric methane (CH4), carbon dioxide (CO2), water intake (Waterin), volatile solids (VS), biodegradable VS (dVS), fecal DM (FDM), fecal water (FW), fecal carbon (FC), fecal nitrogen (FN), total urine (Ut), urine carbon (UC) and urine nitrogen (UN) for lactating cows, nonlactating cows and heifers. Most equations predicted the response variables with reasonable accuracy, except Waterin and Ut equations for nonlactating cows and heifers. In the last chapter, a simulation study was conducted to evaluate the environment impact of dairy cattle and the effect of climate on dairy cattle at the farm level. The ration, body temperature, heat flows, greenhouse gas emission and manure excretion were predicted for two heifer herds, three lactating cow herds and one nonlactating cow herd.

The primary purpose of the study was to assess the effectiveness of different cooling regimes within a liquid cooling garment (LCG) to provide physiological thermal balance and subjective thermal comfort during different intensities of physical exertion. The second purpose was to examine the dynamics of finger temperature (Tfing) and finger heat flux (HFfing) responses to changes in thermal indices reflecting the thermal status of the body core and/or shell. Eight males ages 28.9±8.3 completed an exercise protocol consisting of 4 stages of treadmill walking/running (300-600 Watts) and one rest stage. Four different cooling regimes were tested in separate sessions: subjective cooling control by participant selecting the skin surface cooled (CON1); choice of different inlet water temperatures (Tin), whole body cooling (CON2); fixed Tin; at 7°C, whole body cooling (CON3); adjusted Tin based on different metabolic rates of exercise, whole body cooling (CON4). CON1/2 were acceptable means of LCG cooling control, but showed disadvantages because of delays in self-initiated cooling and frequent failure to select an appropriate cooling intensity. CON3 exhibited the highest amount of heat flow, but was not significantly more effective than CON4 in lowering core temperature (Tcore), heart rate, and perceived exertion. In addition, CON3 caused thermal discomfort and a high level of cold on the skin surface. CON4 appeared an effective cooling regime to support thermal balance and subjective comfort. Sweat rate was positively related to increase in Tcore; however, effects of regional skin wetness on development of thermal discomfort were inconclusive. The dynamics of Tfing/HFfing were highly associated with body heat content and mean body temperature and indicated its potential use as thermal indices to monitor thermal balance of the body. In addition, attention needs to be paid to non-thermoregulatory factors that also influence the dynamics of these indices. The findings suggest that future studies need to focus on harnessing human thermodynamic characteristics to advance the cooling capacity and design of a LCG. The combination of both conductive and convective cooling regimes seems optimal to better support human thermal balance and comfort under physical exertion.

The use of alternative fuels addresses the issues of: reducing dependence on unstable petroleum supplies, reducing harmful emissions, and using renewable energy sources. This thesis focuses on a comparative energy balance on a four cylinder turbocharged diesel engine operating on diesel and biodiesel fuels. Steady-state tests were run to experimentally determine how input energy in the form of fuel was appropriated throughout the engine. The transfer of energy was measured for losses to the engine coolant and exhaust, usable power output, as well as minor and unaccounted losses. The results showed that input energy from biodiesel was distributed 37.4%, 31.1%, and 29.6% to the major areas of coolant, exhaust, and power output, respectively. Similarly the input energy from diesel was distributed 37.5%, 31.4%, and 29.2% to the major areas of coolant, exhaust, and power output, respectively. It was concluded from an uncertainty analysis that there was not a statistically significant difference in these results. Future improvements to obtain distinguishable results are outlined.