Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item On-Farm Dry Matter Analysis to Improve Feed Delivery Precision on Dairy Farms(2011) French, Karin R.; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Uncertainty in dairy ration content impacts feed efficiency, milk production, expenses, and environmental losses. When measuring silage by weight, unknown changes in dry matter (DM) may change the total mixed ration. The objective of this study was to measure variation in silage DM on selected farms and evaluate an electronic method of on-farm DM analysis. Of 31 Maryland farms surveyed, 63% reported DM analysis by an on-farm method, 83% by any method including laboratory measurement. Eight producers performed DM analysis daily for 21 days using a Farmex 1210 Electronic Silage Tester (on-farm) and they recorded precipitation; matching samples were analyzed for DM in a laboratory after oven drying ("standard" method, 55°C followed by 100°C) and by using a Farmex 1210 (laboratory). The standard deviation of mean silage DM varied from 0.72% to 3.33% DM, depending on farm. The electronic method compared poorly to standard DM analysis for most farms.Item UTILIZING SOCIAL NETWORKS ANALYSIS IN THE CHARACTERIZATION OF AFRICAN UNGULATE SOCIAL STRUCTURE(2010) Carpenter, Leah Danielle; Ottinger, Mary Ann; Thompson, Katerina V; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Social networks analysis tools were used to investigate the social structures of two African ungulate species. Captive herds of addra gazelle (Gazella dama) and roan antelope (Hipptragus equinus) were observed. Social networks were constructed of each herd's affiliative (socially cohesive) interactions and nearest-neighbor (closest individual within 2 body lengths) associations during three time periods. I evaluated whether network measures could be explained by individual, dyadic or sub-group attributes at three levels of social network organization. Both roan and addra males were very central to their networks, and in some time periods so were juveniles. Roan and addra partner preferences differed, with addra tending to affiliate by age class while roan were more variable in their partner preferences. Matrilinealy-related sub-groups were also identified in addra. This networks analysis approach has broad applicability for characterizing animal social organizations as well monitoring captive populations.Item CHARACTERIZING THE USE OF BEST MANAGEMENT PRACTICES AND MEASUREMENTS OF PASTURE AND SOIL QUALITY ON MARYLAND HORSE FARMS(2010) Fiorellino, Nicole; Burk, Amy O.; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Agricultural operations, including horse farms, have the potential to negatively affect the environment when managed improperly. The use of best management practices (BMPs) by horse farm operators are important for reducing their farms' environmental impact. Through the use of a mailed survey and field assessment, the use of BMPs on Maryland horse farms was characterized. In general, some BMPs were being used, especially restricting horses from surface water and maintaining vegetative cover. However, BMPs such as correct manure storage and rotational grazing had low adoption rates. A major finding was that soil erosion was a serious problem for most farms and topography, use of compacted materials, and maintenance of vegetative cover can predict occurrence of soil erosion. Results from these studies can aid in the development of future educational events designed to educate horse farm operators about adopting BMPs and preventing pollution of surface water.Item ASSESSMENT OF MALE GIANT PANDA SEASONAL REPRODUCTION, SEXUAL MATURITY AND COMPARATIVE SPERM CRYOTOLERANCE(2010) Aitken-Palmer, Copper; Ottinger, Mary Ann; Howard, JoGayle; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The giant panda is unique as one of the most studied endangered species. Interestingly, despite this, little is known about basic male reproductive physiology. Behavioral problems have posed challenges for reproductive success in the captive population, while geographical isolation and habitat fragmentation threaten the wild population. Techniques such as sperm cryopreservation can improve genetic management and reproductive success within captive populations. But without comparative freeze-thawing studies, diverse methods used for cryopreservation result in inconsistent post-thaw quality, potentially compromising sperm quality and fertility for artificial insemination. This, compounded by limited knowledge of male reproductive physiology, has challenged conservation goals for the giant panda. Specific objectives of this study include: 1) assess the influence of season on male giant panda reproduction by determining annual changes in testis size, body size, testosterone production, sperm quality and production, and reproductive behaviors throughout the year; 2) characterize the onset of sexual maturity in the male giant panda by documenting the timing of initial sperm production, increasing testicular size and body weight, rising androgen production and initiation of reproductive behaviors; and 3) identify factors influencing giant panda sperm cryopreservation by comparing the effect of freeze-thawing on sperm motility, acrosomal integrity, forward progressive movement and longevity. Results provide evidence that 1) reproductive seasonality in the male giant panda is more protracted than the female, with coordinated increases in testes size, androgen production, sperm density, and sexual behaviors; thereby maintaining reproductive competence to prepare for, and accommodate, a brief unpredictable female estrus; 2) sexual maturity in the male giant panda is first observed with consistent sperm production at 5.5 yr, then accompanied by increasing body weight, fecal androgen concentrations, and culminating with the onset of reproductive behaviors, such as scent marking between 7.5 - 8.5 yr; and 3) the giant panda spermatozoon has the capacity to withstand cold stress applied by multiple means, specifically after freezing and thawing using a unique field friendly dry shipper approach. These data greatly improve our understanding of male giant panda reproductive physiology, specifically seasonal rhythms, the cascade of changes associated with sexual maturation, and insights into improved comparative approaches for sperm cryopreservation.Item Understanding the Reproductive Biology of the Przewalski's Horse (Equus ferus przewalskii)(2010) Collins, Christina Wynne; Keefer, Carol ` L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Przewalski's horse (Equus ferus przewalskii) once roamed the Eurasian Steppe but is now considered Critically Endangered with only 1872 individuals remaining in the world, representing progeny from only 14 founder animals (Lee and Boyd, 2008). Genetic diversity needs to be optimal for long term survival of this species. Unfortunately, increasing genetic diversity of the captive population in North America has been hindered by a decrease in fertility. Therefore, the main focus of this research was to characterize reproductive parameters in Przewalski's horse, including estrus cycle in mares and seminal traits in stallions, and determining whether age or inbreeding had an impact on these traits. A secondary focus was to determine whether hormone manipulation of the estrous cycle in mares could be utilized for the long-term goal of using artificial insemination as a breeding management tool for this species. To facilitate these studies, a technique for palpation of Przewalski's mares was developed; the first application of such a procedure in a wild equid. Subsequently, we were able to describe follicular changes in relation to urinary hormone patterns. Fifty percent of the mares had either irregular or acyclic hormonal and follicular patterns. These patterns were directly correlated with inbreeding which is the first time such a correlation has been described in this species. Estrous manipulation was possible using an injectable biorelease form of the progestagen, altrenogest. In stallions, we developed a reliable method of semen collection for Przewalski's stallions and, as a result, describe seminal traits from 98 semen collections from 14 stallions. Based on these collections, we were able to show that sub-fertility in this population could be due to the low percentage of normal spermatozoa. Based on variable analysis, seminal traits total concentration, volume and morphology showed variable changes through the year. Traits also varied on an individual stallion basis. Together, these studies demonstrated that inbreeding is detrimentally affecting the reproductive fitness of this species and that aggressive management is needed for long term sustainability of the captive population.