Animal & Avian Sciences Theses and Dissertations

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    (1994) Davis, Edward S.; Brennan, Miles S.; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
    The cyclophilins are a family of proteins first identified as receptors for cyclosporin A (CsA), a cyclic peptide of fungal origin. CsA inhibits T-lymphocyte activation, and is thus a potent immunosuppressant. Although cyclophilins are ubiquitous, and highly conserved, among eukaryotes, their normal physiological functions are unknown. As the receptors for CsA, cyclophilins might be involved in regulating signal transduction pathways. Cyclophilns also have peptidyl-prolyl, cis-trans isomerase (PPIase) activity in vitro, suggesting a role in protein folding in vivo. While CsA inhibits cyclophilin's PPIase activity, this inhibition is insufficient to account for the pharmacological activity of CsA. Therefore, previous results cannot be readily synthesized into a model for cyclophilin function. The goal of this project was to define and characterize physiological roles of cyclophilins using the yeast S. cerevisiae. Three S. cerevisiae cyclophilin genes were cloned and inactivated by insertional mutagenesis. I demonstrated that one, CPR3, is necessary for the efficient metabolism of non-fermentable carbon sources. The CPR] gene product, Cpr3, is localized to the mitochondrial matrix, and a truncated version of Cpr3 expressed in bacteria binds CsA. CPR3 inactivation does not significantly compromise the induction of transcription of two nuclear cytochrome genes. Thus, Cpr3 is not necessary for the signal transduction pathway governing cytochrome gene expression. To identify biochemical targets of Cpr3, I demonstrated that inactivation of a mitochondrial lactate dehydrogenase is insufficient to account for the growth defect of cpr3 mutants. An exhaustive search for high-copy suppressors of the growth defect of cpr3 mutants led to the identification of a novel gene, JEN1, that suppresses the growth defect at elevated temperature. JEN1 encodes a protein that is probably a lactate transporter, and thus not a direct biochemical target of Cpr3. A dominant mutation in a nuclear gene, JEN2, suppresses the growth defect of cpr3 mutants on lactate at 30°C and 37°C. JEN2 might encode a direct biochemical target of Cpr3. In summary, the cyclophilin, Cpr3, plays a general role in the efficient function of yeast mitochondria, and presents an excellent model system for studying cyclophilin function.
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    (2023) Julianingsih, Dita; Biswas, Debabrata; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In response to escalating consumer demand, a significant number of conventional US poultry farms have transitioned to antibiotic-free and chemical-free practices, particularly those adopting pasture/organic methods. However, recent reports highlight a resurgence of bacterial diseases in both conventional and pasture poultry farms, resulting in elevated bird mortality rates and reduced profitability. This comprehensive study investigates the prevalence of S. Gallinarum and S. Pullorum, causative agents of fowl typhoid and pullorum disease, in integrated crop-livestock/pasture farm environments and meat products. A total of 1,286 samples from 7 farms and 13 retail markets were examined, revealing that S. Pullorum and S. Gallinarum are common in both farm poultry environments and market products. Antibiotic resistance patterns, determined through an antibiogram assay, indicated high resistance to multiple antibiotics. S. Pullorum and S. Gallinarum were discovered in 2.7% and 1.5% of samples, respectively, at the pre-harvest stage. Only 1.6% of the meat samples recovered from retail markets had S. Gallinarum detected in them at the post-harvest level. Concurrently, a different study investigates the possibility of Orange Cold-press Valencia Terpeneless, a citrus oil variety, acting as a natural antimicrobial in poultry farming. This study tackles the problems caused by a decline in the usage of antibiotics, which has resulted in an increase in bacterial infections. Citrus oil exhibits potential as an antimicrobial agent, inhibiting the growth of S. Pullorum and S. Gallinarum, with consistent MIC and MBC values. Time-dependent experiments with 0.4% citrus oil show total suppression of bacterial growth, which is confirmed by environmental simulations. Furthermore, the study reveals that both Salmonella strains have downregulated their virulence genes, which may indicate a change in the pathogenicity of the bacteria. Overall, the findings highlight the crucial importance of surveillance programs and preventive measures. Citrus oil is presented as a promising natural alternative for antibiotics in the treatment of Salmonella-related infections in the poultry farming industry.
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    (2023) Marceau, Alexis; Ma, Li; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Although the history of genetic research has focused on genes and gene products, there is an interesting emerging subclass of genetic elements: long noncoding RNAs (lncRNAs). These are portions of the genome that are longer than 200 base pairs in length and are transcribed from DNA to RNA but do not yield a protein. The function of lncRNA is wide reaching and difficult to define; however, they are predominantly linked to the regulation of gene expression. This is done via transcriptional control, translation control, pre- and post- transcriptional and translational control, epigenetic modifications, RNA processing,as well as other methods. In this dissertation, multiple Bos taurus tissues across various life conditions were investigated in order to identify lncRNA and to begin making predictions about the role and function of identified transcripts. First, lncRNA were identified and analyzed in Bos taurus rumen tissue in pre-weaning and post-weaning cattle. lncRNA were implicated in the weaning process and demonstrated enrichment in complex traits, indicating the continued impact rumen-associated lncRNA have on dairy cattle. Following this study, mammary tissues from dry and lactating cattle were used for lncRNA analysis, in relation to the lacta-tion processes. This study revealed both the presence and impact of mammary lncRNA, and identified lncRNA associated with genes and biological processes that are strongly linked to lactation and mammary tissue function. Subsequently, immune system related tissues were analyzed for lncRNA and their roles. This investigation demonstrated lncRNA to be present in all investigated tissues, including transcripts being repeatedly present. Further analysis into identified lncRNA associated transcripts with genes and functions that are crucial to immune response. Finally, a tutorial was created to make lncRNA identification research more easily accessible to future researchers. The findings and creations of this dissertation increase the knowledge base of lncRNA and their role, allowing for further research endeavors and improvements in Bos taurus husbandry.
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    Metagenomics and molecular tools for monitoring stress conditions and disease susceptibility in rainbow trout
    (2023) Januario, Fabiane C; Salem, Mohamed; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Examining gene transcription alternative splicing can distinguish gene-splicing events associated with stress and identify biomarkers that can be used to monitor stress conditions and decrease sampling invasiveness. Previously, we in silico predicted that a gene called prolyl 4-hydroxylase subunit alpha-2 (P4HA2) with retained intron is expressed under stress conditions. In this study, we aimed to validate the intron's retention and hypothesized that it would continue to show differential expression in fecal and mucus samples. The in vitro expression of the intron verifies the in silico data, where the intron of interest was upregulated during stress conditions. Separately, a microbiome study using the same samples identified bacterial taxa predictive of stress. Higher levels of 3 bacterial biomarker taxa species belonging to the genera Romboutsia and Cetobacterium were more abundant in the stressed fish. However, a pathogenic class of bacteria (Gammaproteobacteria) was significantly higher in the control group.
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    The Life Cycles, Ecology, and Evolution of the Witch-hazel Leaf Gall Aphid, Hormaphis hamamelidis (Fitch) (Homoptera: Aphidida)
    (1987) von Dohlen, Carol Dean; Gill, Doulgas E.; Zoology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
    Two divergent life cycles based on geographic location have been documented for the witch-hazel leaf gall aphid, Hormaphis hamamelidis (Fitch, 1851). At low elevations in northern Virginia, the aphid was found to have seven distinct generations alternating between the primary host, Witch-hazel (Hamamelis virginiana L.), and a secondary host, river birch (Betula nigra L.). These findings confirm the original published life cycle description from the same locality. A second, abbreviated life cycle consisting of only three generations restricted to witch-hazel was discovered at high (1000 m) elevations in north central and northwestern Virginia. Aphids with each life cycle were sympatric at an intermediate elevation site. Based on available life cycle and geographic data, a preliminary Phylogeny of the tribe Hormaphidini is proposed that suggests an unusual polarity in the evolution of aphid life cycles. Several features of intraspecific interactions and host-plant relations were examined in both lowland and highland populations of Hormaphis. In contrast to previous publications documenting severe competition, density effects, and habitat heterogeneity for another galling, host-alternating aphid, Pemphigus betae on Populus angustifolia, the effects of density and host-plant qualities on Hormaphis hamamelidis were fewer and more benign. Aphids did not compete for gall sites, and gall Position and final leaf area did not influence reproduction. High gall densities negatively affected gall growth and aphid fecundity. Factors accounting for the differences in Population dynamics between Hormaphis and Pemphigus are hypothesized and discussed.
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    The study of hyperketonemia in the dairy cow.
    (2023) Barrientos-Blanco, Mario Alberto; Rico, Eduardo; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The metabolic phenomenon of ketosis in dairy cows has remained ambiguous, casting uncertainty over our understanding and its real implications. Ketosis, commonly defined as blood β-hydroxy-butyrate (BHB) ≥ 1.2 mM (i.e., hyperketonemia), has been observationally connected to the onset of peripartal metabolic disorders (e.g., infectious diseases, fatty liver), and reduced milk yield in dairy cows. Although BHB is currently used as standard biomarker for the prediction of negative health and performance outcomes during the peripartum, the nature of this relationship is ambiguous. In contraposition, recent discoveries in mammalian biology indicate BHB as therapeutic metabolite (e.g., alleviation of inflammation and oxidative stress). Our overreaching goal was to study the effects of BHB on dairy cow metabolism and health. In our first study, 6 multiparous (parity = 2.8 ± 0.9) Holstein mid-lactation dairy cows (128 ± 52 days in milk; DIM), were enrolled in a study to evaluate a ketogenic diet using calcium butyrate (—CaBu—; a ruminal ketone precursor) against an un-supplemented control (Control) in a crossover arrangement of treatments. The CaBu resulted in nutritional ketosis (P < 0.05) with blood BHB levels of 0.2 mM higher relative to Control. Although CaBu resulted in reduced dry matter intake (DMI; P < 0.05), milk production was not affected (P > 0.40), and feed efficiencies were improved (P < 0.05) relative to Control. No differences in glucose, NEFA, respiration rates, pain scores, or rectal temperatures were observed between treatments. In the second experiment, 8 multiparous Holstein (2.75 ± 0.89) mid-lactation dairy cows (140 ± 48 DIM), feed ad libitum, were enrolled in a in a crossover arrangement of treatments. The aim of the study was to evaluate the effect of ketones by intravenous infusion of either Na-BHB solution (2.5mM; EK) to sustain hyperketonemia —BHB > 1.2 mM and < 3.0 mM—, or NaCl as a control (2.5mM; Control) over a 72h period. A systemic lipopolysaccharide (LPS) challenge (E. coli 055:B5; 0,085 g/kg BW,) was intravenously administered at h 60 from infusion start. Cows sustained hyperketonemia throughout the 72h experimental period (1.4 BHB mM vs. 0.7 BHB mM in EK vs. Control, respectively). While DMI and milk production were not affected by the BHB infusion, the combination with the LPS challenge resulted in reductions of 20.8% (P < 0.05) and 40.1%, (P = 0.14) for both measurements in EK vs. Control, respectively. No differences were detected in the glucose and NEFA concentrations, but insulin was higher 46.6% (P < 0.05) in EK group. Among the immune markers, IL-1 was 30.8% higher (P < 0.05) in the EK group, and not differences were detected in TNF, IL-10, CRP, and caspase-1. As expected, the LPS challenge induced increased respiration rates, temperature, and pain scores over the time course of the evaluation (P < 0.001); however, respiration rates tended to be reduced in 8.4% (P < 0.1) and rectal temperature increased in 0.3% (P < 0.05) by the BHB treatment (P < 0.05). Our results are indicative that, in the absence of an immune challenge, hyperketonemia results in no negative impact on cow productivity and health. These data add support to our hypothesis that cofactors other than ketones may be necessary for the development of negative trajectories of health and performance of lactating dairy cows. Future studies will be required to confirm that BHB hyperketonemia metabolic effects could differ from ketosis disorder in dairy cows.
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    (2023) Klug, Scott; Porter, Tom E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The pituitary, an endocrine gland primarily regulated by the hypothalamus, secretes multiplehormones and regulates the release of several other hormones from multiple glands within the body. Pituitary development is conserved across vertebrate species and involves a complex temporal and spatial balance of multiple transcription and signaling factor gradients, which control cell commitment, differentiation, and proliferation. Proper pituitary development is critical to survival, since several essential physiological processes are regulated by the pituitary during embryogenesis and throughout life, including metabolism, milk production, stress, reproduction, and growth. Glucocorticoids (GCs) produced by the adrenal glands during embryogenesis play an important role in the differentiation of somatotrophs, the endocrine cell type within the pituitary that produces growth hormone (GH), as well as GH mRNA expression in both avian and mammalian species. In chickens, somatotrophs differentiate between e12 and e16, while mouse somatotrophs differentiate between e15.5 and e17.5. The establishment of the hypothalamic-pituitary-adrenal (HPA) axis and a rise in circulating levels of corticosterone(CORT), the primary GC in rodents and chickens, coincides with somatotroph differentiation and GH mRNA expression in both rodents and chickens. Furthermore, exogenous synthetic GCs such as dexamethasone have been shown to prematurely differentiate somatotrophs in rats and chickens in vitro and in vivo. GCs generate physiological reactions by binding to target cells that express the glucocorticoid receptor (GR). GR, in turn, acts as a transcription factor and regulates the expression of several genes. Despite numerous studies on GH mRNA regulation and somatotroph differentiation by GCs, the mechanism is not completely understood. To better understand the role GR plays in GH regulation by GCs in a mammalian model, mouse embryos with pituitary-targeted GR knockout were generated utilizing the Cre-LoxP Recombinase system under control of the pituitary-specific αGSU promoter. GH mRNA was significantly decreased in GR(-/-) embryos, while GR(+/-) embryos expressed intermediate levels of GH mRNA in comparison to wild-type GR(+/+) embryos. Significant differences in expression of other pituitaryhormones in GR(-/-) embryos were not observed, indicating that GR must not play an essentialrole in regulating the expression of any other pituitary hormone gene. Furthermore, all GR(-/-) embryos died at birth, or soon after. To our knowledge, this is the first study to report homozygous GR knockout in the pituitary suppresses embryonic GH expression and results in a neonatal lethal phenotype.
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    (2022) Scott, Jarvis G; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Atmospheric methane accounts for less than approximately 16% of global anthropogenic greenhouse gas emission. However, it is significantly greater and trapping heat when compared to atmospheric CO2 on a molar lever and any reduction in atmospheric abundance in warranted. Enteric methane from ruminant species accounts for a fraction (< 30%) of the total atmospheric methane however its production also accounts for major dietary energy loss in ruminant species and affects feed efficiency and overall production. Major studies have investigated numerous feed additives and supplements with highly variable finding on the antimethanogenic property of these compounds or feeding strategies, however the findings have raised other questions regarding shifts in VFA profiles accompanying methane inhibition. Higher inclusion levels of concentrate and other nonstructural starch in the diet of ruminants have been shown to decrease methane production and shift volatile fatty acid (VFA) profiles in the rumen. Additionally, many studies have suggested that inhibiting methane production avails as a reducing equivalent to fuel the propionate producing pathway and therefore results in shift in VFA profiles in the rumen. However, very little is understood regarding how these VFA shifts come about. Microbial Kinetics and thermodynamics are physiochemical principles that can be used to study how concentrate inclusion in ruminant diets can change the substrate concentrations and ultimately lead to shifts in fermentation profile in the rumen. Substrate availability supports and/or limits the growth of microbial population in the rumen, while the accumulation of the products or reactants for major fermentation reactions dictate the profile of the VFA. Understanding the role of these physiochemical principles and ultimately the mechanisms involved with changes the profile of VFA and fermentations gas in the rumen would help researchers understand how VFA profiles are shifting during methane inhibition as well as possibly identifying a more targeted approach for inhibiting enteric methane production. Therefore, the objectives of this projects are: to develop an in vitro method to understand the basal kinetic parameters of metabolism in the rumen, to evaluate the effects of increasing forage-to-concentrate ratio on performance and change in in VFA and fermentation gas in vivo, and to test the effect of various perturbations (fermentation metabolites e.g. sodium acetate, sodium lactate etc.) on the fermentation profile of rumen fluid adjusted to different forage-to-concentrate ration. The results indicate that rumen fluid from cows on a high-concentrate diet have a greater capacity to make propionate compared to the high forages diet. The higher propionate production limits the availability of which is necessary for the synthesis of CH4. The finding also suggests that methanogenesis is process limited by substrate concentration. Finally, our studies indicate that feeding strategies targeting enzymatic activity favoring propionate production may be more beneficial than targeting methanogens in a high forage diet.
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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.
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    (2022) McMillian, Zoie Nicole; Weimer, Shawna; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Footpad dermatitis (FPD) is a welfare concern in broiler houses today that is often caused by inadequate management of living conditions. The objective of this study was to evaluate the effect of high-capacity circulation fans on house litter moisture, temperature, relative humidity, noise volume, and broiler body weight, FPD prevalence and severity, hock burn prevalence, feather cleanliness, and behavior from 2 organic commercial flocks. For both flocks, two houses had 16 high-capacity circulation fans (Houses 1 and 2) and two did not (Houses 3 and 4). Welfare assessments took place when the birds were 3 and 6 weeks of age. With both flocks combined, a greater prevalence of FPD (P=0.001) and hock burn (P=0.0002) was observed for birds in the houses without fans than in the houses with fans at week 6. Flock 1 birds in the houses without fans had greater FPD lesion areas (P=0.0001) and FPD severity scores (P=0.0004) than birds in houses with fans. In Flock 2, there were more small birds in the houses without fans at week 6 (P≤0.03). The results of this study indicate that high-capacity circulation fans in commercial broiler houses could positively impact FPD and hock burn prevalence, FPD severity, and flock uniformity.
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    Dietary Control of Cystinuria in Maned Wolves (Chrysocyon Brachyurus)
    (1998) Boniface, Jennifer; Soares, Joseph H., Jr.; Avian and Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    The maned wolf (Chysocyon brachyurus) is an endangered South American species of canid, whose numbers in both the wild and captivity are threatened in part by a condition called cystinuria. In humans and rats, cystinuria is caused by mutations of the rBAT gene, expressed in intestinal mucosal cells and renal tubules. In dogs, only renal tubules are affected. Cystinuric individuals exhibit impaired capacity for reabsorption of the sulfur amino acid cystine. Consequently, excess cystine accumulates in the urine. In acidic conditions, cystine may precipitate into uroliths, potentially obstructing the urethra and ultimately causing bladder rupture or kidney damage. Treatments include medical management and dietary modification. Test diets differing only in levels of cystine were fed to 15 maned wolves in a cross-over design. Apparent digestibility calculations suggest the diets were well received, well utilized and improved fecal quality. The low cystine diet significantly reduced urinary excretion of cystine (P<0.05). Mean urinary concentrations of cystine were 341±45.87 mg/L or 2.78±0.326% total urinary nitrogen for the low cystine diet; and 475.8± 47.80 mg/L or 4.01± 0.342% for the high cystine diet. Water balance studies was determined three maned wolves, using orally administered deuterium oxide. Urine samples were collected daily for seven days, purified by sublimation, and analyzed by infrared spectrometry. It was determined that total body water, water turnover rate and body composition were 17.2 L, 2.3 L/d, and 20.5% fat; 79.5% lean, respectively. These results are comparable to published values for dogs.
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    Regulation of Mitochondrial Metabolism and Lipogenesis
    (2021) Surugihalli, Chaitra; Sunny, Nishanth E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Non-alcoholic fatty liver disease is one of the most common liver disorders with a global prevalence of over 25%. Fatty liver is the most common comorbidity of insulin resistance, obesity, and type 2 diabetes mellitus. During fatty liver, nutrient overload and the associated hyperinsulinemia results in elevated circulating free fatty acids and lipid accumulation in the liver. High rates of lipid accumulation in the liver is partly attributed to high rates of lipogenesis from carbohydrates, together with dysfunctional lipid oxidation. Further, these dysfunctional metabolic networks will induce oxidative stress and inflammation. Thus, understanding the metabolic mechanisms contributing towards the etiology of fatty liver and its associated morbidities is of major interest towards developing prevention and management strategies. This dissertation utilizes a combination of in-vivo (chicken and mice) and in-vitro (isolated mitochondria) systems with stable isotope-based methodologies to study metabolic regulation.Chicken embryos utilize yolk lipids (>45%), deriving over 90% of their energy through lipid oxidation for development. However, during the last few days of incubation and immediately after hatch, there is a substantial induction of lipogenesis. Despite the hepatic lipid overload, the synergistic remodeling of hepatic metabolic networks during embryonic-to-neonatal development blunted inflammatory onset, prevented accumulation of lipotoxic intermediates, and reduced reactive oxygen species production. Elevated plasma branched-chain amino acids (BCAAs) are a characteristic of insulin resistance and are relevant in predicting T2DM. Defects in BCAA degradation networks are also evident in several tissues during insulin resistance and associated co-morbidities. Furthermore, alterations in BCAA metabolism are associated with changes in lipogenesis and mitochondrial oxidative networks. We utilize a combination of isolated mitochondrial systems and stable isotope tracers in diet-induced mouse models of fatty liver, to determine its impact on mitochondrial metabolism and lipogenesis. In summary, the dissertation highlights i) the importance of the natural but dynamic remodeling of hepatic mitochondrial metabolism and lipogenesis during the efficient embryonic-to-neonatal transition in chicken ii) the significance of BCAAs as important regulators of hepatic mitochondrial lipid metabolism. Thus, these studies provide a platform to modulate hepatic metabolic networks and utilize the embryonic-to-neonatal transition phase and dietary intervention of BCAAs as management strategies to alleviate metabolic dysfunctions. 
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    (2021) Magnaterra, Anna; Weimer, Shawna L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Welfare is an important consideration in proper management of broilers. Providing broilers with environmental enrichments may help improve welfare on many levels, and evaluation of potential enrichments is important to ensure they improve broiler welfare. The objective of this study was to evaluate the effect of no enrichments (C), platform (P), spotlight (S), and a combination of spotlight and platform (S&P) enrichments on broiler production, welfare, stress, tibia morphology, tibia ash, and fear behavior. Production, corticosterone, and tibia ash measures were unaffected by enrichments. Compared to other treatments, P broilers had wider (P ≤ 0.02) tibias at 90%, 75%, and 25% length locations and S broilers had narrower (P ≤ 0.04) tibias at 90% and 75% length locations. Fear decreased from week 3 to week 5 (P ≤ 0.05). The results indicate that both platform and spotlight enrichments can influence tibial morphology without decreasing production or animal-based measures of welfare.
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    Immune response after intramammary challenge with Streptococcus uberis mastitis for cows fed OmniGen-AF® during mid-lactation
    (2021) Fischer, Amanda; Kohn, Richard; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Mastitis is one of the costliest diseases in the dairy cattle industry. Environmental pathogens, such as Streptococcus uberis (Strep. uberis), are the most prevalent causes of mastitis infections, while contagious pathogen mastitis has declined in incidences due to improvement in management protocols. Antimicrobials and antibiotics are the primary therapies currently utilized in the dairy industry to treat mastitis. However, the concern for antibiotic overuse and potential bacterial resistance due to improper use of these therapies has steered research in exploration of alternatives to antibiotics or other strategies. One potential alternative is supplementation of an immunomodulatory feed additive to daily cattle total mixed rations (TMR). A current immunomodulator is OmniGen-AF ® (OMN) produced by Phibro Animal Health Corporation (Teaneck, NJ) and has been explored being fed to lactating dairy cattle by previous research groups. OmniGen- AF ® has been reported to improve initial innate immune response during infection. However, it is unknown how OMN influences the innate immune system in vivo to a S. uberis mastitis infection. The ability of OMN to modulate immune function during an environmental mastitis infection was tested compared to control groups. Cows fed OmniGen-AF® and challenged with Strep. uberis had numerically higher least squared mean Log somatic cell count compared to the control group that was not fed OMN and challenged with Strep. uberis. OMN fed cows displayed numerically higher average daily feed intake and fluid milk yield values compared to the control group. Further analysis of milk and blood samples using immunoassays to monitor the effects OMN has on cytokine and cortisol levels throughout mastitis infection is needed to determine innate immune response. In conclusion, OmniGen-AF® has the potential as an immunomodulator that improves innate immune system activity with continuous supplementation in the diet to prevention of dairy cattle environmental mastitis.
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    (2021) Snyder, Ashlyn Marie; Weimer, Shawna; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fast growth rate in broilers comes with welfare concerns and research is needed to determine if fast- and slow-growing broilers differ in pathogen resistance. The objective of this study was to evaluate differences in fast- (FG) and slow-growing (SG) broilers when challenged with Salmonella Typhimurium or broth (control) 14 days post-hatch. Plasma IgA and IgG, jejunum and ileum histomorphology, and behaviors were measured. FG had greater d12 and d24 body weight and d7 jejunum measures, indicating better absorption, and earlier increases in plasma IgA and IgG, indicating earlier immune development. SG had greater d7 IgG, indicating stronger maternal immunity. Post-challenge, FG gut morphology was more impaired, and SG had greater IgA and reduced sham foraging, indicating a stronger immune response to challenge. The results illustrate fast- and slow-growing broilers differ in Salmonella resistance, which can help breeders make selection decisions to prevent Salmonella transmission into the human food supply.
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    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.