Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
2 results
Search Results
Item Thermal balance model for cattle grazing winter range(Montana State University - Bozeman, College of Agriculture, 2005) Keren, Ilai Naftaly; Chairperson, Graduate Committee: Bret E. Olson.Beef cattle grazing semi-arid foothill range of the Northern Rockies during winter may be exposed to cold temperatures and high winds while grazing pastures with low nutritional value. Cattle can physiologically and behaviorally respond to the changing environment to lower metabolic requirements and reduce the effects of cold exposure. Requirements of grazing cattle may be overpredicted with models developed in controlled settings that do not account for energy conserving behaviors. We refined a simple thermal balance equation to model heat exchange of free-ranging cattle. We accounted for the complex interactions between animal behavior and the changing natural environment by applying the insulation characteristics of cattle's tissue and coat to, first, a simple geometric shape of an asymmetric ellipsoid, and second, to a three-dimensional computer model of a cow at different orientations to the sun and wind. A group of mature cows grazing native range were observed from dawn to dusk from 28 November 2003 to 21 January 2004. These observations were used to evaluate our model and as reference for analyzing cattle behavior in response to environmental variables. Correlation (r) between predicted and measured surface temperatures was 0.82, indicating the model successfully quantifies heat exchanges of cattle exposed to cold conditions in the field. We compared our model predictions with heat production measured in three studies, and with predictions based on the National Research Council beef cattle model. In all cases our model predictions were similar to those reported. Model simulations indicate behavior such as lying and orientation to the sun helped mitigate the effects of extreme weather, and that for many combinations of winter weather variables there is only a small increase in metabolic requirements due to cold exposure in mature beef cattle in a maintenance state. Our results indicate solar radiation contributes strongly to a cow's thermal balance. Thus, previous estimates that did not account for the irradiative environment may have overestimated metabolic requirements of acclimated cattle grazing winter range.Item Behavioral consequences of calcium/calmodulin kinase II inhibition in rats(Montana State University - Bozeman, College of Letters & Science, 2005) Schwartz, Elizabeth Ann; Chairperson, Graduate Committee: A. Michael BabcockCaM kinase II (CaMKII) comprises 2% of hippocampal protein and plays an important role in learning and models of neural plasticity. Previous studies have employed a variety of techniques to inhibit CaMKII to investigate its role. This includes the use of chemical inhibition, genetic mutation and antisense; all have shown limitations. In the present study, RNA interference (RNAi) was used to inhibit CaMKII in the hippocampus of rats. The goal of this project was to determine if inhibition of hippocampal CaM kinase would result in behavioral deficits consistent with the role of this kinase. Three behavioral tasks were used to assess behavioral changes associated with a lack of CaMKII in the hippocampus; an open-field task, water maze and T-maze task. An adeno-associated viral vector was used to deliver á CaMKII specific hairpins into rat hippocampi and cDNA for green fluorescent protein (GFP; marker protein). Control animals received AAV that encodes only GFP. In the open-field task, it was hypothesized that experimental rats would show changes in behavior consistent with impaired habituation. This hypothesis was supported; behaviors such as escape attempts and direct versus disorganized movement were significantly different between groups. In the water maze, it was hypothesized that experimental rats would show longer latencies to find the platform in the test phase and spend less time in the target quadrant than control rats during the probe trial. Groups did not differ significantly on latencies to the platform during the test phase but were different during the probe trial. This suggests that experimental rats may be using a non-spatial strategy to locate the platform. In the T-maze, it was hypothesized that the experimental rats would make more errors than control rats due to working memory deficits. This hypothesis was not supported. Densities of á and â subunit CaMKII bands were quantified from digitized images using a computerized densitometry program and á CaMKII was significantly reduced. GFP expression was localized to the hippocampus and extended ± 2 mm from the injection site. Intense áCaMKII staining was observed in control tissue, while staining in was markedly reduced in the experimental condition.