Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Caleb O. Lemley

Committee Member

Derris D. Burnett

Committee Member

Thomas W. Geary

Committee Member

Jean Feugang

Committee Member

Trent Smith

Date of Degree

8-6-2021

Original embargo terms

Worldwide

Document Type

Dissertation - Open Access

Major

Agriculture

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

Early life is critical for the development of an organism. External factors alter placental efficiency which can lead to consequential effects. The objective of the current study was to (1) examine placental characteristics and molecular factors affected by nutrient restriction (2) evaluate the mitigating properties of melatonin in a nutrient restricted pregnancy in regard to circadian, myogenic and adipogenic factors in fetal muscle and (3) evaluate the effects of prenatal and postnatal melatonin supplementation on offspring performance. In study 1, cows were fed a control (CON) or a 60% restricted (RES) diet from day 140 to 240 of gestation. Animals were slaughtered for placentome collection. Nutrient restriction increased vessel perimeter, downregulated genes related to blood vessel development, and upregulated ribosomal and translation factor expression. In lieu of downregulated vessel development, a compensatory effect geared towards nutrient-transport apparent. The 2nd study utilized spring-calving and fall-calving heifers in two trials with a 2 x 2 x 2 factorial design. Treatments were adequately-fed (ADQ) or 60% restricted (RES) dams along with melatonin (MEL) or no melatonin (CON) from day 160 to 240 of gestation. Cesarean sections were performed either in the morning (AM) or afternoon (PM). Circadian, myogenic and adipose-related factors in fetal loin muscle (LM) were analyzed. Fetal LM from the spring-calving (fall) group experienced a downregulation of circadian genes, myogenic genes and tendency for downregulation in lipolysis genes. Fetal LM collected from the fall-calving (summer) group had interactions in myogenic expression. Results demonstrate photoperiod and seasonal effects on nutrient restriction and melatonin supplementation in regard to tissue prioritization. In study 3, melatonin was supplemented to calves during the prenatal and postnatal period in a 2 x 2 factorial design. Supplementation did not alter offspring performance. A lack of differences may be attributed to similar endogenous melatonin levels in dams. Despite no differences in calf performance, tendencies for decreased milk yield and fat were observed in MEL versus CON dams. This demonstrates that melatonin may influence feed efficiency in calves that receive less nutrients during early life. The programming effects of melatonin after birth appear to be low.

Sponsorship

Biophotonics (321653)

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