Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item Characterizing the hypothalamic-pituitary-gonadal axis in turkeys genetically selected for increased egg production(2020) Galleher, Catherine Elizabeth; Porter, Tom E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Within the United States, the turkey industry has historically focused on increased meat production. Studies have shown that there is a negative correlation between meat and egg production. Previous research in our laboratory compared high egg producing hens (HEPH) to low egg producing hens (LEPH). It was found that HEPH express increased levels of mRNA for genes associated with stimulating the hypothalamic-pituitary-gonadal (HPG) axis. We also demonstrated that the hypothalamic-pituitary-thyroid (HPT) axis exerts some effect on egg production. In order to increase our understanding of differences in egg production, we focused on a genetically selected line with increased egg production (E line) and a random bred control line (RBC1). Related to the HPG axis, differences were found related to steroidogenesis and feedback mechanisms. Within the HPT axis, the RBC1 line tended to have increased mRNA levels of genes associated with stimulation of the axis compared to E line.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 BIOLOGY AND MANAGEMENT OF REPRODUCTION IN CAPTIVE CRANES(2017) Brown, Megan Elizabeth; Keefer, Carol L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There are 15 species of cranes found throughout the world, 11 of which are listed as vulnerable or endangered. All 15 species are currently managed in captivity; however, with increased threats to wild crane habitats and populations, ex situ management becomes increasingly critical as a hedge against extinction. Reproduction and the production of offspring is required to ensure self-sustaining populations managed in ex situ conservation breeding programs. However, current reproductive success of the endangered whooping crane (Grus americana), as well as other species, maintained ex situ is suboptimal and hinders population sustainability and reintroduction goals. The objectives of this dissertation were to 1) develop a cryopreservation protocol for crane semen to improve genetic management in endangered cranes, 2) investigated seasonal hormone patterns and measured the impact of captive environment on hormone production and reproductive behaviors, and 3) retrospectively examine the effect of bird as well as management variables on egg fertility in whooping cranes. The findings demonstrated that 1) sperm of both whooping and white-naped crane performed better following cryopreservation when dimethyl-sulfoxide is utilized as a cryoprotectant, 2) seasonal fluctuations occur in hormone production in both sexes, while addition of a water feature to captive enclosures stimulated reproduction in females, and 3) female specific variables had the greatest influence on probability of egg fertility. Overall findings will help whooping crane management Continued research into the mechanisms controlling sperm sensitivity to cryo-damage, egg production, and fertilization are necessary to mitigate reproductive problems in captive crane species.Item Investigating genetic and health factors related to AA amyloidosis prevalence in captive cheetahs (Acinonyx jubatus): implications for population management(2014) Franklin, Ashley Danielle; Porter, Tom E; Crosier, Adrienne E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Systemic amyloid A (AA) amyloidosis is an increasingly important cause of morbidity and mortality among captive cheetahs, yet wild cheetahs are virtually unaffected, suggesting the phenomenon is a result of the captive condition. The self-aggregating AA protein responsible for this disease, is a byproduct of serum amyloid A (SAA) protein degradation, an acute phase protein highly upregulated during inflammation. The objective of this study was to identify the relationship between genetics, stress, and inflammation with serum concentrations of the SAA protein and the incidence of AA amyloidosis in captive cheetahs. Fecal and serum samples collected from cheetahs held at the Smithsonian (NZP-SCBI) and Cheetah Conservation Fund (CCF) facilities, as well as wild, free-ranging cheetahs, were examined. Enzyme-linked immunosorbent assays were used to measure SAA protein and proinflammatory cytokine concentrations in serum samples and cortisol concentrations in feces. Additionally, cheetahs were genotyped for the SAA1A-97delG single nucleotide polymorphism (SNP) in the promoter region of the SAA1 gene. This study was the first to demonstrate that serum concentrations of the SAA protein in cheetahs are affected by the SAA1A-97delG SNP (P=0.0453). However, the high prevalence of AA amyloidosis observed among captive cheetahs is not attributable to genetic differences at this locus, but rather appears to be related to stress and/or inflammation, as captive cheetahs at NZP-SCBI have significantly higher SAA protein concentrations in serum compared to captive cheetahs at CCF, regardless of genotype (P=0.0003). Captive cheetahs at NZP-SCBI show levels of stress (fecal cortisol concentrations) greater than their captive counterparts at CCF in Namibia. Interestingly, wild cheetahs and captive cheetahs at CCF in Namibia had significantly higher proinflammatory cytokine concentrations (TNF-α and IL-1β) in serum compared to cheetahs at NZP-SCBI (P<0.0001). It is possible that chronic stress may be suppressing the production of proinflammatory cytokines in the NZP-SCBI cheetah population. Controlling the currently high SAA protein concentrations associated with AA amyloidosis is the best strategy to decreasing the diseases prevalence among captive cheetahs. Promoting management practices that reduce stress could help re-establish proper immune system homeostasis and mitigate the overproduction of SAA protein, decreasing the probability of developing AA amyloidosis.Item MULTIDISCIPLINARY APPROACH TO UNDERSTANDING THE POOR REPRODUCTION IN THE WHOOPING CRANE (GRUS AMERICANA)(2013) Brown, Megan Elizabeth; Songsasen, Nucharin; Keefer, Carol L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Reproductive success of the endangered whooping crane (Grus americana) maintained ex situ is suboptimal. The main goals of this multidisciplinary investigation are to advance the understanding of whooping crane reproduction and identify potential causes of poor reproductive success in a captive colony. The specific objectives include (Study 1) determining overall seminal characteristics and examine the influences of inbreeding, age, and stages of breeding season on seminal quality in captive birds and (Study 2) utilizing non-invasive endocrine monitoring to longitudinally assess gonadal and adrenal steroids of bird pairs with various reproductive outcomes and evaluating the relationship between hormones and crane behaviors. Our findings demonstrate that (1) there is no relationship between inbreeding coefficient or age and seminal quality of the whooping crane and (2) stage of breeding season impacted seminal output and characteristics. Overall estradiol concentrations and reproductive behaviors, but not glucocorticoid levels, were also key determinants to successful reproductive output.Item Characterization and Control of Aggression and Reproduction in the Male Clouded Leopard (Neofelis nebulosa)(2012) DeCaluwe, Heather Burton; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Clouded leopards are a striking and elusive cat species whose secretive nature has made it difficult to gather information on population statistics and behavior in the wild, where the population is in decline. While captive populations are intended as a hedge against extinction, breeding clouded leopards ex situ has been a challenge, primarily due to extreme male aggression toward females. Despite the importance of aggression in this species, there has as yet been no systematic study characterizing the basis of aggressive episodes. Two mechanisms seem to underlie the aggressive behavior in clouded leopards: degree of anxiety and circulating testosterone levels. Three studies were conducted to characterize mechanisms modulating aggression in male clouded leopards. In Study 1, sixteen adult male clouded leopards were categorized as `anxious' or `calm' using a keeper questionnaire and fecal endocrine (androgen and glucocorticoid) profiles; these measures were correlated with behavior rates and frequencies before, during, and after a series of behavioral reaction tests aimed at assessing an individual's response to stress-inducing situations. In Study 2, the behavioral and endocrine responses to the same tests were compared in the same clouded leopards following three treatments: 1) an anxiety-reducing psychotropic drug (clomipramine, n = 4); 2) a gonadotropin releasing hormone agonist (deslorelin, n = 5), or 3) no treatment (n = 4). In Study 3, the long-term effects of the drug treatments on spermatogenesis and hormone concentrations were compared in clouded leopards (n = 2/treatment) and domestic cats (n = 5/treatment), a model for non-domestic felid reproduction. Studies revealed important findings about the basis of aggressive behavior in male clouded leopards. First, two of the behavioral reaction tests - `mirror image stimulation' and `unfamiliar people' - were effective tools for evaluating temperament and eliciting a behavioral response. Second, treatment with both clomipramine and deslorelin reduced anxious and aggressive behaviors (e.g. `tail flicking' and `growling') indicating multiple physiological mechanisms likely modulate aggression in this species. Finally, deslorelin temporarily suppressed hormone concentrations and reproductive function, while clomipramine had no clear effect on either. Ultimately, this information provides important tools for improving male-female pairing success and the overall management of captive clouded leopards.