Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item Investigating Copper Acquisition And Delivery via Transporters and a Pharmacological Chaperone in Copper-Deficient Worms and Mice(2019) Yuan, Sai; Kim, Byung-Eun; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Copper (Cu) is a key micronutrient required for a variety of essential biochemical pathways. Systemic or tissue-specific Cu-deficiencies, caused by insufficient dietary Cu uptake or mutations in Cu transporting genes, result in impaired growth, neuropathy, ataxia, hypopigmentation, osteoporosis and anemia-like symptoms in mammals. How organisms regulate Cu homeostasis at the systemic levels in response to Cu deficiencies remain elusive. In this study, we use Caenorhabditis elegans (C. elegans), a genetically tractable, multi-tissue metazoan to explore Cu homeostasis and investigate these unknowns. The high-affinity Cu transporters encoded by CTR family genes are required for dietary Cu uptake and maintaining systemic Cu balance from yeast to mammals. However, little is known about Cu acquisition mechanisms in C. elegans. We identified ten CTR ortholog genes in C. elegans; of these, chca-1 was functionally characterized. Cu availability regulates transcription of chca-1 in both the intestine and hypodermis, and chca-1 is essential for normal growth, and reproduction in the worm. Additionally, altered Cu balance caused by the loss of CHCA-1 results in defects in Cu-responsive avoidance behavior. Identification of this CTR-like gene in C. elegans, which appears to be essential for normal Cu homeostasis in the worm, illustrates the importance of Cu delivery via CHCA-1 for normal metazoan development and behavioral phenotypes. In addition, we show that a Cu-binding pharmacological chaperone, elesclomol (ES), fully restores the developmental defects and Cu deficiencies in chca-1-depleted worms, as well as the lethality in worms lacking cua-1 expression (Cu exporter ATP7A ortholog), suggesting ES is able to efficiently deliver Cu from dietary sources to peripheral tissues through the intestine in C. elegans. Our study was further expanded to mammalian models such as cardiac-specific Ctr1-depleted (Ctr1hrt/hrt) mice. We found that ES administration fully restores the postnatal lethality, developmental defects and cardiac hypertrophy found in Ctr1hrt/hrt mice, as well as rescuing the secondary systemic Cu homeostasis responses, including aberrant ATP7A protein levels in the liver and intestine. Moreover, ES shows the potential ability to transport Cu across the blood-brain-barrier in in vitro studies. These results illustrate the capability of ES to rescue systemic Cu deficiency in worms and mice, independent of the presence of functional Cu transporters, and shed light on the therapeutic usage of ES in Cu-deficient human diseases.Item Identification of the molecular networks governing ovulation frequency in low and high egg producing turkey hens(2019) Brady, Kristen Marie; Porter, Tom E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Selection for carcass traits has negatively impacted and varied the reproductive efficiency of the commercial turkey hen, creating overall lowered egg production as well as distinct groups of low egg producing hens (LEPH) and high egg producing hens (HEPH). Ovulation frequency correlates with egg production and differs between LEPH and HEPH. Ovulation is governed primarily by the hypothalamo-pituitary-gonadal (HPG) axis through a preovulatory surge (PS) of luteinizing hormone (LH) and progesterone (P4) but ovulation can be influenced by the hypothalamo-pituitary-thyroid (HPT) axis. Dysregulation of the thyroid and reproductive axes, disrupting the PS, leads to lowered egg production, leaving the poultry industry to compensate with larger breeding flocks. LEPH exhibited hypothalamic and pituitary expression consistent with decreased ovulation stimulation and increased ovulation inhibition as well as decreased steroid synthesis in follicle cells. Neuroendocrine and ovarian tissues from HEPH showed a higher sensitivity and response to in vitro HPG axis stimulation. Moreover, cells from HEPH responded positively to HPG axis inhibition while cells from LEPH responded negatively, indicating functional differences in HPG axis regulation. RNA sequencing results reinforced the higher expression of HPG axis genes in HEPH and showed higher expression of HPT axis genes in LEPH. Estradiol (E2) was identified as an upstream regulator activated in HEPH. Hens with average egg production (AEPH) also showed upregulation of E2 receptors during the PS, suggesting involvement in positive feedback loops. Supporting the role of E2 in neuroendocrine feedback, higher plasma concentrations of E2 were seen during the PS in HEPH. Looking into the HPT axis, LEPH displayed lower plasma concentrations of triiodothyronine (T3) and higher levels of thyroxine (T4) outside of the PS while HEPH displayed lower levels of T3 and higher levels of T4 inside of the PS. The T3 and T4 levels surrounding the PS in HEPH were consistent with levels seen in AEPH. At a molecular, cellular, and endocrine level, the reproductive physiology of LEPH and HEPH differs, ultimately leading to egg production differences. Studies tying the noted differences to egg production rates will allow for identification of genetic markers to increase the reproductive efficiency of commercial breeding hens.Item ANTIBIOTIC ALTERNATIVES FOR TREATMENT OF MASTITIS IN DAIRY CATTLE(2019) Scholte, Cynthia Madeleine; Moyes, Kasey M; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mastitis is one of the most costly diseases to the dairy cow industry. Implementation of management protocols have decreased the incidence rate of contagious mastitis pathogens, while the incidence of cases caused by environmental pathogens, such as Escherichia coli (E. coli) and Streptococcus uberis (Strep. uberis), remains unchanged. Currently, antibiotics are the primary therapy utilized to control mastitis. However, growing concern for antibiotic overuse, improper use and bacterial resistance have led to the examination of alternative strategies. Two promising alternative mitigation strategies were explored in the research leading to this dissertation. The first is a potent endolysin, PlyC, which has demonstrated bactericidal activity against several streptococcal species in a variety of applications. However, it is unknown how PlyC interacts with the bovine immune system. Varying doses of PlyC were non-toxic and did not alter the oxidative burst response of bovine neutrophils, the first immune cells recruited to the intramammary infection. The second alternative to an antimicrobial drug explored was citrus oil dissolved in ethanol. This was tested against E. coli strain P4. Prior antimicrobial investigations with citrus oil utilized dimethylsulfoxide as a carrier solvent, which is currently prohibited in the dairy industry. Citrus oil and its primary components were tested to determine minimum inhibitory, bactericidal and biofilm eradication concentrations. Citrus oil components, citral and linalool, demonstrated better antimicrobial activity than the native oil in vitro. In addition, citral and linalool were minimally toxic to bovine neutrophils and did not hinder their oxidative burst response in vitro. Because citral demonstrated greater antimicrobial activity than linalool, it was the logical candidate to test for the efficacy as an intramammary therapy against experimentally-induced E. coli mastitis. Unfortunately, citral treatment did not differ from a common intramammary antibiotic therapy or sterile buffered solution. In conclusion, the use of PlyC as an alternative therapy for Strep. uberis mastitis is promising as PlyC may not interfere with immune response during mastitis. The antimicrobial effects of citral may better serve as a disinfectant than a therapy for E. coli mastitis.Item ESTIMATION OF DRY MATTER INTAKE AND IDENTIFICATION OF DIETARY AND PRODUCTION PARAMETERS THAT INFLUENCE FEED EFFICIENCY OF INDIVIDUAL DAIRY COWS(2019) Iwaniuk, Marie Elizabeth; Erdman, Richard A.; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The objectives of this dissertation were to: 1) develop and validate equations used to estimate individual cow dry matter intake (DMI; kg/d) based on a nitrogen (N) balance approach, 2) determine the discriminatory power of several biological, production, and dietary variables on dairy feed efficiency (FE) as defined as energy-corrected milk (ECM; kg/d) per unit of DMI, 3) repeat the second objective using residual feed intake (RFI) to indicate FE status, and 4) determine if RFI values are dependent on the equation utilized to estimate DMI. Results from the first experiment (Chapter 3) indicated that DMI could be successfully estimated on an individual cow basis using the following commonly measured parameters: milk yield, milk protein concentration, body weight (BW; kg), and dietary N concentration. These inputs are relatively simple to measure; therefore, this equation may be used in the dairy industry as a practical method to estimate individual cow DMI when cows are fed in a group setting. The results of the second experiment (Chapter 4) suggested that days in milk (DIM), milk fat yield (g/d), and BW had the most discriminatory power (89% success rate) to discriminate between cows based on their FE status when FE was defined as ECM per unit of DMI. Therefore, dairy producers can use these 3 variables to select for cows with high FE without requiring the measurement of DMI which can be costly and difficult to obtain. Observations from the third experiment (Chapter 5) suggested that RFI is indicative of differences in metabolic efficiency between cows independent of most biological, production, and dietary variables, except DIM. These results are consistent with other studies that have suggested that RFI is indicative of true differences in metabolic efficiency between cows regardless of production parameters. Lastly, the results of the fourth experiment (Chapter 6) suggest that RFI values generated from different DMI equations are strongly correlated such that RFI values are independent of the DMI equation utilized in the calculation. Thus, dairy producers can select the equation to estimate DMI that is most suitable for their operation without causing an “equation bias” on the RFI calculation.Item Effect of grazing muzzles on grazing miniature horse behavior and physiological stress(2019) Davis, Kristina; Burk, Amy O; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Grazing muzzles are highly effective at reducing forage intake in horses and are a popular tool to control horse weight. However, grazing muzzle design may cause horses stress. The objective of these studies was to determine how grazing muzzles impact behavior and physiological stress in grazing horses. Two groups of 6 miniature horses, housed individually or in a herd, wore grazing muzzles for 0, 10, and 24 h/d. Over 9 weeks, body weight, heart rate parameters, salivary cortisol concentrations, and observations of behavior were collected. Results indicate muzzling did not seem to cause physiological stress as measured by cardiac and salivary cortisol parameters but did alter grazing and locomotive patterns. Muzzling for 24 h/d was necessary for weight loss and was associated with lower heart rate and higher heart rate variability. These findings suggest that muzzles do not cause stress in horses, even if left on for 24 h/d.Item COMMUNITY STRUCTURES OF GUT MICROBIOME UNDER DIFFERENT DIETS IN ANGUS BEEF CATTLE(2019) Liu, Jianan; Song, Jiuzhou; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The microbiota of animals’ digestive tract plays important roles in health, nutrient utilization, and performance. For ruminants, the digestive tract, including rumen and other gastro-intestinal regions, hosts a unique and diverse microbiome that aids feed fermentation, digestion, and absorption. We hypothesize that compositions of diets can influence microbiomes and further affect the production of VFA and the composition of bile acids in beef cattle. We used rectum microbiota as a baseline and examined the microbiome in rumen and jejunum by16S-seq, together with quantifications of VFAs, lactate, and bile acids under grass-feeding and grain-feeding. We found that microbial communities displayed significant differences in microbiome structure and VFA production. Moreover, increased VFAs in grain-fed group may trigger lactate-associated bacteria growth. Bile acids could promote the growth of bacteria that had abilities of secondary bile acids conversion. These results provided deep insights into differences in beef quality and bovine biology under different diets.Item MODULATING KEY GENES INVOLVED IN PANCREAS FORMATION AND INSULIN SIGNALING USING CRISPR/CAS9 IN THE PIG(2019) Sheets, Timothy P; Telugu, Bhanu P; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Among the metabolic diseases, diabetes remains a “pressing problem” as recognized by World Health Organization, not only due to the impact on individuals’ lives, but also because of the rapid increase in newly diagnosed patients. To better understand the mechanisms of diabetes, this dissertation investigates the role of NGN3 in pancreas development using CRISPR/Cas9 gene targeting in the pig model. NGN3 was selected for study because of its critical role in endocrine pancreas formation. Our research demonstrates that the targeted ablation of NGN3 blocks development of the endocrine pancreas, a finding supported through gene expression analysis. Furthermore, follow-up studies show that clonal piglets derived from NGN3-ablated animals lack the major endocrine islet cell types and subsequent expression of key endocrine hormones. This porcine model provides valuable insights into the study of type 1 diabetes in early post-natal life and future applications of human-to-pig chimeric organ development for transplant surgery. Expanding upon this porcine model for diabetes, we sought to apply this approach to the study of type 2 diabetes using a novel pig model, thus bridging the gap between mouse and human. For this endeavor, we identified GRB10 as a potential critical mediator in insulin signaling, development, and growth potential following an extensive literature review. The potential for dual applications in both agriculture and medicine was also identified as an objective. Analysis of qPCR data from in vitro overexpression studies supports that GRB10 modulates insulin signaling through the canonical insulin pathway. Additional data from two in vivo gene editing trials targeting the GRB10 locus in both Ossabaw and domestic pig breeds show a supportive qualitative trend towards growth regulation in the Ossabaw pig breed. Further evidence is required to determine whether GRB10 plays the same role in the domestic pig, as a limited cohort size of mutants precluded an extensive analysis of phenotypes. Together, our assessment of NGN3 and GRB10 offer significant potential for modeling of both type 1 and type 2 diabetes as well as modeling of growth traits in the pig through application of advanced genome engineering technology.Item SUPPLEMENTAL CHOLINE AND METHIONINE FOR DAIRY CATTLE: EFFECTS ON PERFORMANCE, LIVER FAT CONTENT AND GENE EXPRESSION, AND PLASMA AMINO ACID AND CHOLINE METABOLITE CONCENTRATIONS(2019) Potts, Sarah B; Erdman, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The objectives of this dissertation were to 1) determine markers of post-ruminal choline supply so that bioavailability of rumen-protected choline (RPC) sources can be calculated in lactating cows and 2) investigate the production performance and metabolic effects of supplemental choline, methionine, or both on periparturient dairy cows. Observations from Experiment 1 indicated that of the 26 choline metabolites investigated, including 16 species of phosphatidylcholine (PC) and 4 species of lysophosphatidylcholine, free choline and betaine in blood and milk were most responsive to post-ruminal choline supplied via abomasal infusion. However, RPC did not elicit changes in blood or milk choline metabolites, even at the very high doses tested in Experiment 2. These results suggest that choline supplied as RPC is absorbed differently than choline supplied via abomasal infusion, that RPC is over-protected such that choline supplied in this form is not available to the cow, or that responses to RPC vary depending physiological state of the cow. Results from Experiment 2 indicated that primi- and multiparous cows respond differently to supplemental choline and methionine fed during the periparturient period. Feeding RPC to primiparous cows increased milk yield, while feeding rumen-protected methionine (RPM) had minimal effects on production. In contrast, RPM improved milk components and fat-corrected milk yield for multiparous cows. These observations suggest that primi- and multiparous cows have different methionine and choline requirements in the periparturient period. Investigation into the specific metabolic effects of choline and methionine fed to periparturient cows in Experiment 3 suggested that both RPC and RPM modify choline metabolism. The milk and blood PC profile was altered by both RPC and RPM. In line with this observation, RPC increased hepatic expression of the gene that encodes the enzyme responsible for catalyzing the rate-limiting step of PC synthesis via the CDP-choline pathway. The RPC-induced increase in hepatic betaine-homocysteine methyltransferase expression provided additional support for the connection between choline and methionine metabolism via one-carbon metabolism. Modification of postpartum plasma lactate concentrations by RPC for both primi- and multiparous cows, in conjunction with alterations in pre- or postpartum body condition, also suggest a choline-induced modification of tissue mobilization.Item EVALUATION OF A METHOD TO MEASURE VOLATILE FATTY ACIDS AND GASES IN VITRO WITH MATHEMATICAL MODELING(2018) Judd, Latisha Marquita; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Methane emissions from ruminants have become an issue over the last 50 years. Previous research has shown that methane emissions are stoichiometrically linked with volatile fatty acid (VFA) profiles in ruminant animals. For example, a shift from acetate to propionate may decrease carbon dioxide (CO2) and hydrogen (H2) production, and in turn, decrease conversion of CO2 and H2 to methane. In vitro methods have been developed to measure the digestibility of feeds, but such methods may not accurately estimate methane or volatile fatty acid (VFA) profile. The development of in vitro methods to accurately estimate gas production and VFA profile in rumen fermentation would enable isolation of fermentation effects from various animal interactions. Therefore, the focus of this dissertation was to develop an in vitro method that will have the same VFA and gas profiles as in the rumen. The objectives of this project are: to develop an in vitro technique that mimics an in vivo rumen environment in order to study VFA profiles and gas production during fermentation, to examine and evaluate the efficacy of selected feed additives (e.g. probiotics) on VFA profiles and gas production, and to develop a mechanistic model of the in vitro fermentation system and the effects of feed supplements on the system. The results indicate that gas profile, VFA profile, and gas production were affected by differing in vitro fermentation conditions (buffering capacity, headspace gas composition, acetate concentration). A review of the literature was conducted to establish the effect of probiotics such as lactic acid bacteria on in vitro and in vivo systems. These findings indicated Enterococcus and Lactobacillus species tended to affect ruminal fermentation parameters. Further in vitro analysis of these probiotics indicated these bacteria tended to affect ruminal fermentation, such as gas and VFA production. A developmental mechanistic model was built to predict whether the effect of probiotics was thermodynamically or kinetically limiting. Future studies will further development of this simple model by using published literature for a meta-analysis that may aid in further interpretation of rumen fermentation regarding thermodynamic limits and maximal efficiency of key rumen fermentation reactions.Item Genetic Architecture of Complex Traits and Accuracy of Genomic Selection in Dairy Cattle(2018) Jiang, Jicai; Ma, Li; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Genomic selection has emerged as an effective approach in dairy cattle breeding, in which the key is prediction of genetic merit using dense SNP genotypes, i.e., genomic prediction. To improve the accuracy of genomic prediction, we need better understanding of the genetic architecture of complex traits and more sophisticated statistical modeling. In this dissertation, I developed several computing tools and performed a series of studies to investigate the genetic architecture of complex traits in dairy cattle and to improve genomic prediction models. First, we dissected additive, dominance, and imprinting effects for production, reproduction and health traits in dairy cattle. We found that non-additive effects contributed a non-negligible amount (more for reproduction traits) to the total genetic variance of complex traits in cattle. We also identified a dominant quantitative trait locus (QTL) for milk yield, revealing that detection of QTLs with non-additive effect is possible in genome-wide association studies (GWAS) using a large dataset. Second, we developed a powerful Bayesian method and a fast software tool (BFMAP) for SNP-set association and fine-mapping. We demonstrated that BFMAP achieves a power similar to or higher than existing software tools but is at least a few times faster for association tests. We also showed that BFMAP performs well for fine-mapping and can efficiently integrate fine-mapping with functional enrichment analysis. Third, we performed large-scale GWAS and fine-mapped 35 production, reproduction, and body conformation traits to single-gene resolution. We identified many novel association signals and many promising candidate genes. We also characterized causal effect enrichment patterns for a few functional annotations in dairy cattle genome and showed that our fine-mapping result can be readily used for future functional studies. Fourth, we developed an efficient Bayesian method and a fast computing tool (SSGP) for using functional annotations in genomic prediction. We demonstrated that the method and software have great potential to increase accuracy in genomic prediction and the capability to handle very large data. Collectively, these studies advance our understanding of the genetic architecture of complex traits in dairy cattle and provide fast computing tools for analyzing complex traits and improving genomic prediction.