Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item Post-bottleneck inbreeding accumulation reduces fitness in laboratory populations of Tribolium castaneum under environmental stress(2008) Choiniere, Ashley Danielle; Siewerdt, Frank; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Populations are often driven to extinction due to low genetic diversity. One major cause for loss of genetic diversity in a population is a demographic bottleneck. A demographic bottleneck was imposed on twenty-one populations of Tribolium castaneum using multiple strategies. After recovering to original census numbers, the populations were subjected to stressful environments, and fitness was quantified. There was a significant decrease in additive genetic variance in all populations as a result of the bottleneck event (P<0.05). As estimated inbreeding accumulation increased, there was a decrease in the mean of fitness related traits, such as adult weight, total progeny, fecundity and survivorship. This relationship was best explained using quadratic models and became even more significant when the populations were under stress. This suggests that both dominance and epistatic gene effects are playing a role in phenotypic expression of traits and that expression may be flexible, supporting survival and fitness.Item Developing a Methodology for the Assessment of Freedom of Movement: The Influence of Spatial Parameters on Movement and Space Use in Mice (Mus musculus)(2008-11-26) Brooks, Raymond Matthew; Stricklin, William R; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite recent progress in developing housing conditions that more effectively meet the needs of managed species, there remains a lack of detailed information regarding the influence of a space on animal health and well-being. If improvements are to be made to current guidelines so that they accurately reflect the needs of the animals, this information and a reliable method for collecting it, is critical. The objective of this project was to systematically examine the effects of spatial parameters on movement and space use of mice (Mus musculus) in open-field arenas. This approach may provide researchers with a means to describe what factors are most important for maintaining an adequate welfare state, and may help address questions regarding why (and how) these factors function as they do. To accomplish this, a standardized method was used across three experiments to test the effects of floor area, arena shape and structural complexity on movement and space use of mice. In each experiment 40 female Swiss Webster mice were observed in four arenas differing in spatial characteristics. In Experiment One, mice were individually observed in four square arenas that differed in floor area (0.5, 1, 2 and 4m2). The results from this experiment demonstrated an effect of both floor area and perimeter length on movement and space use of mice, as measured by track length, area traversed and mean distance to the nearest wall. In Experiment Two, the same variables were used to describe the behavior of mice in four arenas of equal floor area (1.5m2) that differed in shape (circle, square, 2:3 rectangle or 1:3 rectangle). Observation of animals in a circular arena demonstrated the impact of corner space on continuity of movement. In the final experiment, partitions were added in pre-determined configurations to examine the influence of partition location on animals demonstrating thigmotaxis. While the addition of partitions affected the distribution of movements, the specific location of partitions had little impact on movement or space use. With some refinement, this methodology could be used across species to identify specific needs and determine how effective housing systems are at meeting them.Item Separating the Effects of Group Size, Density, and Enclosure Size on Movement and Use of Space in Domestic Fowl (Gallus gallus domesticus)(2008-04-24) Leone, Erin Hoerl; Estevez, Inmaculada; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This project was designed to separate the confounded effects of group size, density, and enclosure size, and to examine the role of enclosure design and its related parameters in shaping movement patterns and use of space in the domestic fowl. While previous research has suggested that group size, density, and enclosure size are highly relevant to broiler (meat-type chicken) welfare, confounding between variables makes their individual contribution difficult to distinguish. My novel treatment structure with 10, 20, and 30 birds in small (1.5 m2), medium (3.0 m2), and large (4.5 m2) enclosures enabled me to determine the impact of enclosure size while systematically controlling for group size and density. Three enclosure designs: rectangular, square, and square with partitions to maintain a constant perimeter to area ratio, were employed in order to determine the impact of enclosure parameters such as length to width and perimeter to area ratio. Enclosure size and design were the most relevant factors for space use, which was immune to the influence of group size and density. Birds consistently had larger home ranges in larger enclosures. The design of the enclosure had a strong effect of movement, altering the response of birds to the treatment combinations. Movement appeared to be greatest in rectangular enclosures, where the largest straight-line distance is available and the perimeter to area ratio declines at a relatively slow rate with increasing enclosure size. While enclosure size played a significant role in determining nearest neighbor distances and net displacement, these parameters appeared to be limited by density. The presence of partitions designed to increase interior perimeter space appeared to reduce movement and increase inactivity. Movement patterns did not appear to be restricted by social interactions for any group size. Rather, the physical presence of group mates at even a relatively low density of 6.7 birds/ m2 appeared to act as a barrier to group dispersal and movement. Group size had little effect on young domestic fowl. Overall, this project has shown that for young domestic fowl the most relevant factors to overall space use are the amount of space available and enclosure design.Item EPIDEMIOLOGIC ANALYSIS OF RISK FACTORS FOR LOCAL DISAPPEARANCES OF NATIVE RANID FROGS IN ARIZONA(2005-08-11) Witte, Carmel Lee; Kane, Andrew S.; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study used epidemiologic case-control methodology to examine habitat and environmental factors contributing to amphibian declines in Arizona. Risk factors were compared between sites where frogs disappeared (cases) and persisted (controls) using univariate and multivariable logistic regression analyses. Thirty-six percent (117/324) of all sites became cases during the study period. Elevation, non-native predators, hydrologic characteristics, aspect, and effects of nearby sites were significantly associated with frog persistence or disappearance. In the final multivariable model, risk for disappearance increased with increasing elevation (OR=2.7 for every 500 meters, P<0.01). Sites where disappearances occurred were 4.3 times more likely to have other nearby sites that also experienced disappearances (P<0.01), while having an extant population nearby decreased risk of disappearance by 85% (OR=0.15, P<0.01). Sites experiencing disappearances were 2.6 times more likely to have crayfish than control sites (P=0.04). Identification of risk factors associated with frog disappearances will guide future research and conservation efforts.Item Neuronal Activation Following Cohabitation in the Prairie Vole (Microtus ochrogaster)(2004-04-29) Hazelton, Julie Louise; Ottinger, Mary A; Hoffman, Gloria E; Keefer, Carol L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sexually naïve female prairie voles require exposure to a novel male to activate the neural circuits involved in the formation of stable pair bonds and to stimulate sexual receptivity. The objective of our study was to investigate the neural pathways involved in the formation of pair bonds. Cushing et al. (2003) studied neuronal activation in selected brain regions, as expressed by c-Fos immunoreactivity (ir), during the first hour of cohabitation in prairie voles. In the present study, we extend the findings of this study to examine neuronal activation associated with cohabitation to include 2, 6 and 12 hr. In addition, we examined the potential colocalization of luteininzing hormone releasing hormone (LHRH) and c-Fos to determine if this is a system activated during the initial stages of pair bond formation. The selected time periods include the initiation of sexual activation of the female and pair bond formation. Expression of c-Fos as analyzed in three regions that play a role in early social encounters. These areas included: (1) the sociosexual behavior circuit, (2) the reward pathway, and (3) nuclei whose peptides regulate the actions of those networks. Based on the previous data, increased c-Fos expression was predicted in the social behavior circuit, including the medial amygdala, bed nucleus of the stria terminalis, medial preoptic nucleus, and ventromedial nucleus of the hypothalamus. The lateral septum was examined due to its role in the social behavior circuit and in the process of pair bond formation. Next, we predicted that increased c-Fos activity would be observed over time in regions that did not show increases during initial contact, but are involved in pair bond formation. These regions include two components of the reward pathway: the nucleus accumbens and the ventral pallidum. Finally, nuclei known to regulate both the social behavior and reward circuits were examined and included the supraoptic nucleus and the pariventricular nucleus, which produce oxytocin and vasopressin. These neuropeptides are critical in social behavior and the formation of pair bonds. Immediately following the period of cohabitation (0, 1, 2, 6 or 12 hour in length) animals were separated and brains fixed. Fixed brains were sectioned at 30μm and stained with c-Fos and LHRH antibodies using double label immunocytochemistry (ICC) (Berghorn et al., 1994). Significant colocalization of LHRH and c-Fos was not observed in the first twelve hours in either sex of cohabitated prairie voles. Additionally there was no difference in number of LHRH ir neurons between sex or treatments. LHRH ir neurons in male and female prairie voles were predominantly located in the diagonal band of broca, preoptic area, lateral hypothalamus and supraoptic decussation. Individual LHRH neurons that did express c-Fos were predominantly located in the POA and LH. We observed a sexually dimorphic temporal pattern in c-Fos ir in the circuitry involved in pair bond formation in prairie voles. This pattern suggests that incoming information is first sorted through the social-sexual circuit and continues to be processed as information is received by nuclei of the reward pathway a short time later in both sexes. An increase in immediate early gene (ieg) immunoreactivity in the social behavior network is reported concurrently with peak activation of the reward circuit. During the same time period, an increase in c-Fos ir is reported in the nuclei involved in the endocrine control of partner preference and pair bond formation. Together these data suggest that in prairie voles, both the social and reward circuits interact early in cohabitation prior to reproductive activation to establish a heterosexual bond and that both circuits may be regulated by neuropeptides produced by the PVN and SON. This research was conducted by funding from the following: NSF IBN-9817024 (MAO), NIH HD 38490 (CSC, GEH, BSC, MAO) and MH 01992 (BSC). Subject Category: Neuronendocrine Activation following cohabitation Keywords: LHRH, social behavior, reward pathway, c-Fos, neuronal activation