College of Agriculture & Natural Resources

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Now showing 1 - 6 of 6
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    Pathogenicity and Transmissibility of North American H7 Low Pathogenic Avian Influenza Viruses in Chickens and Turkeys
    (MDPI, 2019-02-16) Chowdhury, Ishita Roy; Yeddula, Sai Goutham Reddy; Kim, Shin-Hee
    Low pathogenic avian influenza (LPAI) viruses can silently circulate in poultry and wild aquatic birds and potentially mutate into highly pathogenic avian influenza (HPAI) viruses. In the U.S., recent emergence and spread of H7N8 and H7N9 HPAI viruses not only caused devastating losses to domestic poultry but also underscored the capability of LPAI viruses to mutate into HPAI viruses. Therefore, in this study, we evaluated pathogenicity and transmissibility of H7N8 and H7N9 LPAI viruses (the progenitors of HPAI viruses) in chickens and turkeys. We also included H7N2 isolated from an outbreak of LPAI in commercial chickens. H7 viruses replicated more efficiently in the respiratory tract than in the gastrointestinal tract, suggesting that their replication is restricted to the upper respiratory tract. Specifically, H7N2 replicated most efficiently in two-week-old chickens and turkeys. In contrast, H7N8 replicated least efficiently in those birds. Further, replication of H7N2 and H7N9 was restricted in the upper respiratory tract of four-week-old specific-pathogen-free (SPF) and broiler chickens. Despite their restricted replication, the two viruses efficiently transmitted from infected to naïve birds by direct contact, leading to seroconversion of contacted chickens. Our findings suggest the importance of continuous monitoring and surveillance of LPAI viruses in the fields.
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    Transcriptomic Analysis of Inbred Chicken Lines Reveals Infectious Bursal Disease Severity Is Associated with Greater Bursal Inflammation In Vivo and More Rapid Induction of Pro-Inflammatory Responses in Primary Bursal Cells Stimulated Ex Vivo
    (MDPI, 2021-05-18) Asfor, Amin S.; Nazki, Salik; Reddy, Vishwanatha R.A.P.; Campbell, Elle; Dulwich, Katherine L.; Giotis, Efstathios S.; Skinner, Michael A.; Broadbent, Andrew J.
    In order to better understand differences in the outcome of infectious bursal disease virus (IBDV) infection, we inoculated a very virulent (vv) strain into White Leghorn chickens of inbred line W that was previously reported to experience over 24% flock mortality, and three inbred lines (15I, C.B4 and 0) that were previously reported to display no mortality. Within each experimental group, some individuals experienced more severe disease than others but line 15I birds experienced milder disease based on average clinical scores, percentage of birds with gross pathology, average bursal lesion scores and average peak bursal virus titre. RNA-Seq analysis revealed that more severe disease in line W was associated with significant up-regulation of pathways involved in inflammation, cytoskeletal regulation by Rho GTPases, nicotinic acetylcholine receptor signaling, and Wnt signaling in the bursa compared to line 15I. Primary bursal cell populations isolated from uninfected line W birds contained a significantly greater percentage of KUL01+ macrophages than cells isolated from line 15I birds (p < 0.01) and, when stimulated ex vivo with LPS, showed more rapid up-regulation of pro-inflammatory gene expression than those from line 15I birds. We hypothesize that a more rapid induction of pro-inflammatory cytokine responses in bursal cells following IBDV infection leads to more severe disease in line W birds than in line 15I.
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    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.
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    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.
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    ENERGY METABOLISM IN DEVELOPING CHICKEN LYMPHOCYTES DURING THE EMBRYONIC TO POSTHATCH TRANSITION
    (2007-07-26) Rudrappa, Shashidhara Govindareddy; Porter, Tom E; Humphrey, Brooke D; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In chickens, the primary energy substrate is lipid during embryogenesis and carbohydrate after hatch. Accordingly, chicks adapt their metabolism to utilize glucose after hatch; however, little is known about metabolic adaptation in developing lymphocytes. Therefore, the objective of this dissertation was to examine metabolic adaptation in developing lymphocytes and the associated impact on their development. The first objective examined energy substrate utilization in bursacytes and thymocytes during the embryonic to posthatch transition. Glucose metabolism increased in both lymphocyte populations during the first two weeks posthatch due to increased glucose transporter-3 mRNA abundance, glucose uptake and hexokinase activity. Additionally, some of these metabolic markers were positively correlated with the serum glucose concentration. Glutamine metabolism increased in bursacytes only, and lipid metabolism was unaltered in both populations. Collectively, glucose is a preferred energy substrate for lymphocytes posthatch, and glucose utilization by developing lymphocytes may be related to the serum glucose concentration. The second objective determined the effect of glucose availability on thymocyte metabolism, energy status and survival. Embryonic thymic lobes were grown in culture in media containing varying glucose concentrations. Thymocyte glucose metabolism and mitochondria membrane potential were highest in 15 mM glucose and apoptosis was highest in 5mM glucose. Collectively, glucose availability regulates glucose metabolism in thymocytes, and these changes in glucose metabolism were related to thymocyte energy status and survival. The third objective determined the effect of glucose availability on T cell development. Thymocyte Interleukin-7Rα (IL-7Rα) mRNA abundance and CD4+ T cell numbers over the culture period were dependent upon glucose availability. Between 12 and 24 h, thymocyte IL-7Rα mRNA abundance increased in 5 mM increased 1.74-fold, while it decreased in 15 mM by 58.6%. CD4+ numbers decreased with time in 5 mM, whereas they increased with time in 15 mM. T cell receptor (TCR) β excision circles were higher in 15 mM compared to 5 mM at 12 h. Glucose availability alters TCR β rearrangement, IL-7Rα gene expression and CD4+ T cell development, which may influence naïve T cell generation. As thymocytes develop in a low glucose environment in ovo, this may be one factor that limits T cell development until hatch.
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    FORAGING STRATEGIES, USE OF SPACE AND AGGRESSIVE BEHAVIOR OF DOMESTIC FOWL (Gallus gallus domesticus)
    (2004-05-03) Hoerl, Erin Natalie; Estevez, Inma; Animal Sciences
    Domestic fowl were tested in three experiments, all investigating the mediating effects of three group sizes of 5, 10, and 20 individuals, on behavioral responses under varying environmental conditions. The first experiment investigated social spacing and aggressive behavior in the presence or absence of cover panels. Smaller group sizes were more affected by cover panels than larger group sizes. In the second and third experiments patchy environments were used to test optimal foraging strategies. In the second experiment, smaller group sizes were more affected by patch locations than larger ones. In the third experiment birds were presented with patches varying in quality. Birds in all group sizes were able to immediately discern patch quality and preferred patches of higher quality. Despite generations of artificial selection pressure domestic fowl continue to forage optimally in patchy environments, and adopt flocking strategies predicted by behavioral ecology theory.