Animal & Avian Sciences Theses and Dissertations

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    Vertical Resource Partitioning and Sexuality of Three Sympatric Species of Red Sea Sandfishes (Xyrichtys melanopus, Labridae; Trichonotus nikii, Trichonotidae; Gorgasia sp., Congridae)
    (1988) Krall, Marianne Martha; Clark, Eugenie; Zoology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    Three species of marine sandfishes were studied from 1984 to 1986. Their inter- and intraspecific behavior was monitored during the daylight hours to examine interactions that could result in the vertical stratification of the species over the sandy bottom within the fringing and patch reefs in the north Red Sea. Horizontal plankton tows were taken at three heights and three times a day. These samples were compared to stomach contents of the fishes to determine the trophic relationships in the community and their affects on spatial relations between the species . Prey specificities of the fishes were determined by using an electivity measure. Using paraffin histology, Xyrichtys melanopus was determined to be a monandric protogynous hermaphrodite and Trichonotus nikii, a gonochorist. Previous work on the mating systems and territoriality of all three sandfish species helped in part to explain the vertical spatial arrangement of the sandfish species within the community. Effects of pollution on the b iota of the Northern Gulf of Aqaba are noted.
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    (2022) Mathkari, Chirantana Vikas; Dennis, Rachel L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Breeding purpose Japanese quail (Coturnix japonica) are often maintained in barren cages with little environmental complexity. These conditions can lead to unwanted social interactions and stress-related behaviors that can cause serious injury, mortality, and reduce productivity. Use of environmental enrichments has shown to improve poultry well-being; however, the optimal enrichments for quail have not been widely studied. The aim of this project was to evaluate the effectiveness of various enrichments on the well-being and productivity of breeding quail colonies (1 male, 2 females/cage). The enrichments studied were designed to reduce unwanted interactions and stress-related behaviors by either providing a shelter (protective enrichments) or by providing mental stimulation (stimulatory enrichments). In Experiment 1, using an incomplete Latin square design, each cage received one protective enrichment (Hut, Plastic leaves, or Grass), or one stimulatory enrichment (Mirror, Feeder toy, or Mat), or no enrichment (control) (average n=17/treatment). In Experiment 2, using an incomplete Latin square design, each cage received one of the following enrichment combinations: Hut + Mirror, Hut + Feeder toy, Hut + Mat, or only Hut (average n=14/treatment). Parameters measured included behaviors, body weight, Hen Day Egg Production (HDEP), egg weight, physical scores, and fecal corticosterone metabolites (FCM) levels. Measures were analyzed using a one-way ANOVA or Chi-square test on SAS 9.4. The results indicate that exposure to a single enrichment reduced stress-related damaging behaviors and increased resting; while exposure to a combination of enrichments reduced a larger variety of stress-related damaging behaviors more efficiently. Two of the three protective enrichments (Hut, Grass) exerted a notable impact on production, while combinations of protective and stimulatory enrichments were more efficient in decreasing physical scores as compared to a single enrichment. The Hut + Mat combination notably reduced the FCM levels as compared to only Hut. Our study identified enrichments which are optimal for improving breeding quail well-being, and exhibit the potential to improve the economics of the quail industry.
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    (2022) Bina, Parinaz; Taneyhill, Lisa A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The trigeminal ganglion contains the cell bodies of sensory neurons comprising cranial nerve V and functions to relay information related to pain, touch, and temperature from the face and head to the central nervous system. Like other cranial ganglia, the trigeminal ganglion is composed of neuronal derivatives of two critical embryonic cell types, neural crest cells and placode cells. Neurogenesis within the cranial ganglia is promoted by Neurogenin2, which is expressed in trigeminal placode cells and their neuronal derivatives, and transcriptionally activates neuronal differentiation genes like Neuronal Differentiation 1 (or NeuroD1). Other targets downstream of Neurogenin2 and NeuroD1 include Drebrin1 and Stathmin2, cell polarity and cytoskeletal regulators that mediate changes in neuron cell shape during neurogenesis. Little is known, however, about the role of Neurogenin2, NeuroD1, and their downstream signaling pathways during trigeminal gangliogenesis in the chick embryo. By depleting Neurogenin2 and NeuroD1 from chick trigeminal placode cells with morpholino antisense oligonucleotides, we examined how these proteins influence chick trigeminal ganglion development. Additionally, we identified the expression of Drebrin1 and Stathmin2 in trigeminal ganglion neurons. Taken together, our results highlight, for the first time, functional roles for Neurogenin2 and NeuroD1 during chick trigeminal gangliogenesis. These studies will not only improve our understanding of the molecular mechanisms underlying trigeminal ganglion development, but may also provide insight into human and animal diseases of the peripheral nervous system.
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    The Genetic Architecture of Complex Traits and Diseases in Dairy Cattle
    (2022) Freebern, Ellen; Ma, Li; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Genetic architecture refers to the number and locations of genes that affect a trait, as well as the magnitude and the relative contributions of their effects. A better understanding of the genetic architecture of complex traits and diseases will be beneficial for analyzing genetic contributions to disease risk and for estimating genetic values of agricultural importance. In particular, genetic and genomic selection in dairy cattle populations has been well established and exploited through genome-wide association studies, sequencing studies, and functional studies. The objective of this dissertation is to understand the genetic architecture of complex traits and apply the understanding to investigate the biological relationship between genetics and diseases in dairy cattle. First, we performed GWAS and fine-mapping analyses on livability and six health traits in Holstein-Friesian cattle. From our analyses, we reported significant associations and candidate genes relevant to cattle health. Second, we evaluated genome-wide diversity in cattle over a period of time by running GWAS and proposed a gene dropping simulation program. From this study, we identified candidate variants under selection that are associated with biological and economically important traits in cattle. Also, we demonstrated that gene dropping is an applicable method to investigate changes in the cattle genome over time. Third, we investigated the effect of maternal age and temperature on recombination rate in cattle. We provided novel results regarding the plasticity of meiotic recombination in cattle. Additionally, we found a positive correlation between environmental temperature at conception and recombination rate in Holstein-Friesian cows. Collectively, these studies advance our understanding of the genetic architecture and the biological relationship between complex traits and diseases in dairy cattle.
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    (2022) Aditya, Arpita; Biswas, Debabrata; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Enterohemorrhagic Escherichia coli O157: H7 (EHEC), a foodborne enteropathogen, remains a significant public health concern since its discovery in 1982. With an incredibly low infectious dose (10-100 bacteria), this pathogen can cause self-limiting diarrhea, vomiting, and abdominal cramps. However, more complicated disease conditions such as bloody diarrhea or hemolytic colitis have been known to develop depending on the serotype involved in the infection, and on immune status and/or age of the patients. Due to its Shiga toxin (Stx) production ability, EHEC infection may lead to a kidney-related problem known as hemolytic uremic syndrome (HUS), which requires advanced medical care. Unlike other bacterial illnesses, therapeutic administration of antibiotics to treat EHEC infections is not recommended due to their controversial association with Stx production. As a result, only preventative/prophylactic and immune-supportive strategies are followed for EHEC infections. Using the antibacterial properties of probiotic bacteria and the metabolites they produce are promising alternative strategies for preventing EHEC infections. We have targeted the probiotic bacteria Lactobacillus casei to determine the mechanism of this alternative strategy. In our study, we have executed microbiological, molecular, chromatographic, and metagenomic approaches to determine the antagonistic mechanisms of action of their metabolites, specifically conjugated linoleic acid (CLA) produced by Lactobacillus casei, against the growth and metabolism of EHEC. The metabolites of wild-type L. casei (LCwt) were augmented by supplementing it with a prebiotic-like dietary component, namely peanut flour (PF) (LCwt+PF), while another LCwt was also genetically engineered (LCCLA) to over convert CLA from linoleic acid (LA). These modifications showed effective results in controlling EHEC both in vitro and in ex vivo conditions. Total metabolites present in cell-free culture supernatant (CFCS) of LCwt, LCwt+PF, and LCCLA were able to control the growth of EHEC without negatively hampering the relative abundance of Firmicutes and Bacteroidetes present in rumen fluid (RF). Among these CFCSs, CFCSCLA exerted the most desirable outcome by eliminating EHEC. In vitro studies demonstrated that, a lower concentration of purified CLA worked synergistically with other metabolites of LCwt and augmented their inhibitory activity against EHEC. The orchestrated effect of metabolites has been observed to downregulate the virulence genes, disrupt the cell membrane, interfere with cell division, and damage their genomic DNA. The probable effect of these metabolites, specifically CLA, on Stx production and neutralization was also investigated by assessing host cell cytotoxicity. Total metabolites of Lactobacillus spp. as well as CLA itself, showed improvement in cell survivability when exposed to Stx. Our findings established a ground to explore the effect of specific metabolites obtained from probiotic bacteria in control and prevention of EHEC. The findings also showed a promising association of purified CLA in neutralizing Stx which can be further explored to use it in therapeutic purposes.