Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item Effect of Air on Rumen Gas Production(2021) Rha, Rachel Youngah; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ruminants may swallow air as they eat and ruminate throughout the day. However, it is unclear as to how the introduction of oxygen impacts fermentation pathways, bacteria, and yeast within this mostly anaerobic environment. Therefore, the focus of this thesis was to study air’s impact on rumen fermentation and to determine if probiotics could offset air’s impact on digestibility. An in vitro analysis of air and probiotics indicated the main effect of air decreased digestibility, the main effect of probiotics had variable effects, and probiotics had significant interactions with air. The interactions suggested yeast employing a potential alternative pathway with the introduction of oxygen. Utilizing published literature, a static and dynamic mathematical model was built to further analyze digestibility, gas composition, and uptake of oxygen within the rumen. Future studies will further develop this model with in vivo studies to further interpretation and understanding of rumen fermentation’s complex system.Item EXPOSURE EFFECTS OF ENVIRONMENTAL GESTAGENS ON THE REPRODUCTIVE BEHAVIOR AND FITNESS OF THE FATHEAD MINNOW (PIMEPHALES PROMELAS)(2016) Frankel, Tyler Edward; Orlando, Edward F; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Historically, endocrine disrupting chemical research has focused on environmental androgens, estrogens, thyroid hormones, and their antagonists. Recent efforts have begun to examine the effects of gestagens, which include endogenous progestogens and synthetic progestins, on aquatic organisms. Gestagens have been measured in wastewater treatment plant effluent, pulp mill effluent, and runoff from agricultural fields. While studies have documented profound effects on the reproduction of fish and amphibians, the effects of gestagen exposure on reproductive behavior and male gamete quality have been relatively unexplored. As such, a series of studies were conducted in which fathead minnows (Pimephales promelas) were exposed to either a water control, EtOH control, or one of two concentrations of gestodene (GES), levonorgestrel (LNG), or progesterone (P4) using a flow-through exposure system. Egg deposition was quantified daily, and alterations of reproductive behavior were examined on days 1, 2, and 8. After 8 days, fish were examined for the presence of secondary sexual characteristics (i.e. nuptial tubercle, fin spot, and dorsal fatpad formation). Egg deposition was affected by all treatments, with complete cessation observed at higher concentrations. Reproductive behaviors were affected after just one day in response to both treatments of LNG, GES, and P4, with effects continuing through days 2 and 8. Exposure to both concentrations of LNG and GES also caused the physical masculinization of female fathead minnows. In a second set of studies using computer assisted sperm analysis, the same treatments were utilized to determine effects on sperm motility in males as a result of in vivo or in vitro exposure. LNG and GES showed no effect in either study, and P4 caused decreases in sperm motility only as a result of in vivo exposure. Together, results from this study indicate that both GES and LNG function as environmental androgens in fishes, causing masculinization of secondary sex characteristics in females and disruption of reproduction over a short period of time. As altered reproductive behavior was observed after just one day of exposure for all treatments, this study underscores that behavior is an extremely sensitive endpoint that merits increased attention in future aquatic toxicology studies.Item THE EFFECTS OF POLYCHLORINATED BIPHEYNLS (PCBs) ON AVIAN CARDIAC DEVELOPMENT(2012) Carro, Tiffany; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polychlorinated biphenyls (PCBs) are a class of synthetic organochlorines that are thermally stable, resistant to degradation, and persistent in the environment as a result of bioaccumulation and intermittent redistribution through trophic levels. These compounds were sold commercially as mixtures in the twentieth century and later banned due to their biological toxicity. There are 209 known PCB congeners, each with different toxicities and physical properties that cause a variety of adverse health effects. Moreover, the effects of PCB mixtures vary with exposure concentrations, PCB congener toxicity, and species sensitivity. However, limited information is available about the impact of PCBs on the development of the embryonic cardiovascular system. There is a major site of contamination along the upper Hudson River in New York; wildlife in that region have shown evidence of exposure to PCBs. The purpose of this research was to determine the impact of embryonic exposure to a PCB mixture and a single congener, both found in the upper Hudson River on the developing avian cardiovascular system. In study 1, tree swallow eggs (Tachycineta bicolor) were dosed with PCB 77 and incubated to hatch. Similarly, domestic chicken eggs (Gallus domesticus) were dosed with the PCB mixture at embryonic day zero and incubated to hatch in study 2. Eggs were monitored through incubation; other measures were taken at hatch along with tissue collection. Results showed that embryonic exposure to PCBs resulted in an absence of the ventricular wall compact layer and hypertrabeculation in tree swallow hatchlings in spite of no effect on survival. Embryonic exposure to a PCB mixture in domestic chickens resulted in compact layer absence as well as additional cardiomyopathies, including absence of the ventricular wall trabeculated layer, ventricular chamber dilation, abnormal heart wall and septal formations, and arrhythmias during embryonic development. In study 3, embryonic exposure to a PCB mixture was studied at Hamburger Hamilton stages 10, 16, and 20. Embryonic exposure to a PCB mixture resulted in abnormal proliferation of cardiomyocytes early in heart development. Dose-dependent mortality occurred in chicken embryos exposed to the PCB mixture. These results support other findings demonstrating PCB effects on the cardiovascular system. Further, these data showed dramatic adverse effects of the PCB mixture as well as a single congener found in the region of the upper Hudson River on the developing avian cardiac system.