عنوان
پدید آورنده
موضوع
رده
کتابخانه
محل استقرار
NATIONAL BIBLIOGRAPHY NUMBER
Number
TL51269
LANGUAGE OF THE ITEM
.Language of Text, Soundtrack etc
انگلیسی
TITLE AND STATEMENT OF RESPONSIBILITY
Title Proper
Identification of the Molecular Networks Governing Ovulation Frequency in Low and High Egg Producing Turkey Hens
General Material Designation
[Thesis]
First Statement of Responsibility
Brady, Kristen M.
Subsequent Statement of Responsibility
Porter, Tom E.
.PUBLICATION, DISTRIBUTION, ETC
Name of Publisher, Distributor, etc.
University of Maryland, College Park
Date of Publication, Distribution, etc.
2019
GENERAL NOTES
Text of Note
271 p.
DISSERTATION (THESIS) NOTE
Dissertation or thesis details and type of degree
Ph.D.
Body granting the degree
University of Maryland, College Park
Text preceding or following the note
2019
SUMMARY OR ABSTRACT
Text of Note
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.
UNCONTROLLED SUBJECT TERMS
Subject Term
Animal sciences
Subject Term
Endocrinology
Subject Term
Molecular biology
PERSONAL NAME - PRIMARY RESPONSIBILITY
Brady, Kristen M.
PERSONAL NAME - SECONDARY RESPONSIBILITY
Porter, Tom E.
CORPORATE BODY NAME - SECONDARY RESPONSIBILITY
University of Maryland, College Park
ELECTRONIC LOCATION AND ACCESS
Electronic name
مطالعه متن کتاب p
[Thesis]
276903
a
Y
