Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Caleb O. Lemley

Committee Member

Brian J. Rude

Committee Member

Derris Devost-Burnett

Committee Member

Hector L. Sanchez-Rodriguez

Date of Degree

8-6-2021

Original embargo terms

Worldwide

Document Type

Dissertation - Open Access

Major

Agricultural Sciences

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

The circadian rhythms are not solely regulated by photoperiod but are also influenced by feed regimen. Therefore, maternal nutrient restriction during gestation could potentially impact the fetal circadian rhythm. Melatonin, a circadian rhythm modulator hormone, has shown to act as an antioxidant reducing reactive oxygen species during stress exposure; and two potential mechanisms have been proposed for melatonin causing vasoconstriction and vasodilation regulating blood flow. In livestock species, nutrient restriction during gestation reduces uterine blood flow, limiting nutrients availability to the fetus for growth and development. Therefore, this project aimed to use beef heifers to evaluate the maternal nutrient restriction and/ or melatonin supplementation in (1) temporal transcript abundance of clock genes, angiogenic factors and nutrient sensing genes in bovine placenta, (2) temporal alterations of uteroplacental blood flow, vaginal temperatures, and placentome vascularization, and (3) fetal morphometrics. Early maternal nutrient restriction did not alter placental explants gene expression. Furthermore, the maternal portion of the placentome exhibited limit temporal variation, while the fetal tissue exhibited a clear temporal rhythm in the mRNA relative abundance of the genes measured. Additionally, melatonin supplementation during late gestation, showed to increased uterine blood flow, reduced vaginal temperatures, and rescued fetal weights during compromised pregnancies in a season dependent manner. In conclusion, the bovine placenta exhibited an autonomous circadian rhythm, while the fetal and maternal circadian rhythms appeared to be independent systems. Future research should examine the effects of melatonin supplementation in fetal organ development.

Sponsorship

Agriculture and Food Research Initiative Competitive Grant no. 2018-67016-27580 from the USDA National Institute of Food and Agriculture.

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