Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
Browse
5 results
Search Results
Item Genetic Variation in Nitrogen and Phosphorus Levels in Broiler Excreta: Opportunity for Improving both Birds and the Environment(2010) sasikala appukuttan, arun kirshna; Siewerdt, Frank; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The increase in poultry meat consumption has resulted in intensified poultry farming operations with consequent concentration of excreta in major production areas. The nutrient content in the soil surrounding the poultry farms has increased as a result of the high content of nitrogen (N) and phosphorus (P) in the poultry excreta. The current study aimed to propose a strategy to reduce the N and P content in excreta through genetic selection of broilers for efficient nutrient utilization. The traits measured (on a dry matter basis) were the percentage of N in the excreta (PNE) and the percentage of P in the excreta (PPE). Individual 24-hr excreta samples were collected from 6 wk old birds. Excreta samples were collected from a commercial breeding farm at two different time periods from line A and line B birds respectively, and analyzed for PNE and PPE. Analysis of excreta samples collected during the first period (197 bird samples belonging to 15 sire families) and second period (278 birds belonging to 25 sire families) suggested a heritability of 0.08, 0.16 for PNE and 0, 0.20 for PPE, respectively. Phenotypic and genetic correlations between the measured traits from the two lines were very low; however, phenotypic correlation analysis of PNE and PPE with other traits of commercial interest showed some favorable as well as neutral associations. Blood samples collected from the birds were used for an association study of the excreta traits with four candidate genes. The candidate genes were selected based on the results of previous research. Some of the SNPs from the candidate genes were found to have additive and dominance effect on the excreta and production traits and were usually favorably associated with mutations in higher frequency in the populations. The results suggest that genetic selection of birds for PNE and PPE could improve the environment and the market value of the birds.Item DELINEATING THE ROLES OF C. ELEGANS HEME RESPONSIVE GENES HRG-2 AND HRG-3 IN HEME HOMEOSTASIS(2009) Chen, Caiyong; Hamza, Iqbal; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heme is an essential cofactor for diverse biological processes such as oxygen transport, xenobiotic detoxification, and circadian clock control. Since free heme is hydrophobic and cytotoxic, we hypothesize that within eukaryotic cells, specific trafficking pathways exist for the delivery of heme to different subcellular destinations where hemoproteins reside. To identify molecules that may be involved in heme homeostasis, we conducted a C. elegans microarray experiment on RNA extracted from worms grown at different concentrations of heme in axenic liquid medium. Analysis of the microarrays revealed that the mRNA levels of heme-responsive gene-2 (hrg-2) and hrg-3 increased more than 70 fold when worms were grown at 4 µM compared to 20 µM heme. hrg-2 is expressed in hypodermal tissues in the worm, and the protein localizes to the endoplasmic reticulum and the apical plasma membrane. In vitro hemin agarose pull-down experiments indicate that HRG-2 binds heme. Deletion of hrg-2 in C. elegans leads to reduced growth rate at low heme. Moreover, expression of HRG-2 in hem1δ, a heme-deficient yeast strain, results in growth rescue at submicromolar concentrations of exogenous heme. These results indicate that HRG-2 may either directly participate in heme uptake or facilitate heme delivery to another protein. Unlike hrg-2, hrg-3 is exclusively expressed in the worm intestine under heme deficiency. Following its synthesis, HRG-3 is secreted into the body cavity pseudocoelom. Deletion of hrg-3 results in increased heme levels in the worm intestine, suggesting that HRG-3 may function in intercellular heme transport in C. elegans. To identify the functional network or pathways for HRG-2 and HRG-3, we performed a genome-wide microarray analysis using RNA samples prepared from the worms grown at different concentrations of heme and oxygen. The results showed that a total of 446 genes were transcriptionally altered by heme and/or oxygen. Among them, 41 and 29 genes exhibited similar expression profiles to hrg-2 and hrg-3, respectively. We postulate that these genes may function in conjunction with hrg-2 and hrg-3. Taken together, we have identified two novel heme-responsive genes in metazoa that may play critical roles in modulating organismal heme homeostasis in C. elegans.Item ASSOCIATION OF SINGLE NUCLEOTIDE POLYMORPHISMS WITH PHENOTYPIC PRODUCTION TRAITS IN BROILER CHICKENS(2009) Liu, Xuan; Porter, Tom E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research investigated the association between SNPs and phenotypic production traits in fat and lean chicken broiler lines. In previous research, eleven SNPs in the promoter regions of four candidate genes were selected. In this study, significant associations were detected between AKR1B10 SNP1 and SDC1 SNP1 and fat yield. SDC1 SNP1 was significantly associated with fat weight. SOD3 SNP2 was associated with breast yield. Five sire-SNP interactions and one sex-SNP interaction were significant. There was a significant interaction between sex and SDC1 SNP3 on muscle-related factor. GPC3 SNP1 interacted with time period on body weight from week 1 to week 9. QTLs on chromosomes 1, 3 and 4 for body fat were refined by incorporating these SNPs into QTL analysis. These genetic markers may be of great value for marker-assisted selection (MAS) for chickens with less abdominal fat as well as genetic markers for body fat accumulation in humans.Item Post-bottleneck inbreeding accumulation reduces fitness in laboratory populations of Tribolium castaneum under environmental stress(2008) Choiniere, Ashley Danielle; Siewerdt, Frank; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Populations are often driven to extinction due to low genetic diversity. One major cause for loss of genetic diversity in a population is a demographic bottleneck. A demographic bottleneck was imposed on twenty-one populations of Tribolium castaneum using multiple strategies. After recovering to original census numbers, the populations were subjected to stressful environments, and fitness was quantified. There was a significant decrease in additive genetic variance in all populations as a result of the bottleneck event (P<0.05). As estimated inbreeding accumulation increased, there was a decrease in the mean of fitness related traits, such as adult weight, total progeny, fecundity and survivorship. This relationship was best explained using quadratic models and became even more significant when the populations were under stress. This suggests that both dominance and epistatic gene effects are playing a role in phenotypic expression of traits and that expression may be flexible, supporting survival and fitness.Item Quantitative Trait Loci and Promoter Analysis of the Bovine Butyrophilin Gene(2004-01-27) Zegeye, Abiy; Mather, Ian H; Animal SciencesThe butyrophilin gene (BTN1A1) has been described in all mammalian species so far investigated. BTN1A1 is a likely QTL candidate that affects an economically important trait in dairy animals because it is specifically expressed in lactating mammary tissue and the gene product BTN1A1 may function in the secretion of milk lipid. Five PCR-RFLP intragenic markers were identified. Three of the five markers are bi-allelic, however, the two 5'-most markers may be multiallelic loci. The markers were further used to conduct a QTL analysis to examine any allelic substitution effects on economically important milk production traits, namely, total protein, percent protein, total fat, percent fat, somatic cell score, herd life, and milk yield. One significant effect was detected for percent protein. Other effects were not significant, but this could possibly be due to the skewed allelic frequency distribution, or because the variable nucleotides were either intronic or coded for a conservative amino acid substitution. The 5' flanking region of bBTN was cloned and sequenced. Computational and transient transfection assays were conducted to identify regions of bBTN that are important for its expression. A computational analysis was conducted to compare and analyze the 5' flanking region of cow, goat, human and mouse sequences. Several regions of homology were identified that code for shared binding motifs. However, neither the transcription start site (TSS) nor the other segments of similarity in the proximal promoter region were analogous to other 'milk protein genes' such as the caseins and α-lactalbumin, and other widely studied non-mammary-specific genes. Transient transfection assays in HC11 cells indicate the region from -1kb to -0.45 kb is sufficient to drive the expression of a reporter gene. bBTN appears to contain a novel set of elements that define the (TSS) and proximal promoter modules. A more incisive examination will circumscribe the major cis-acting elements.