Date of Completion

Spring 5-1-2022

Thesis Advisor(s)

Steven A. Zinn

Honors Major

Animal Science

Disciplines

Sheep and Goat Science

Abstract

Poor maternal nutrition during gestation negatively impacts fetal programming and the development of the hypothalamic-pituitary-ovarian axis in the offspring. Reproductive health of ewes can be characterized by concentrations of reproductive hormones including follicle stimulating hormone (FSH), luteinizing hormone (LH), and progesterone, particularly during the estrous cycle. We hypothesized that ewes born to dams that experienced poor maternal nutrition during gestation would have reduced reproductive capability and efficiency. This means that they would take longer to become pregnant and have reduced concentrations of reproductive hormones compared with those born to mothers fed the control diet. Pregnant dams (F0) were fed one of three different diets beginning on day 30 of pregnancy, restricted-fed (RES: 60%), control-fed (CON: 100%), or over-fed (OVER: 140%) based on National Research Council (NRC) requirement for total digestible nutrients. The female offspring (F1) of these dams were fed the same postnatal diet that met the requirements for growing ewe lambs. Thirty-eight multiparous yearling Dorset ewes (F1 generation) were estrous synchronized using the protocol previously described (Jones et al., 2016). Briefly, a controlled intravaginal drug releasing device (CIDR) was placed through vaginal insertion and released progesterone over a 12-day period. After this period, CIDRs were removed and ewes were given an intramuscular injection of prostaglandin (PG) F2α to stimulate luteolysis. After synchronization, ewes were divided evenly and placed with one of two related rams. Blood samples (10 mL) were collected by jugular venipuncture every 7 days from synchronization until one week after confirmation of pregnancy by transabdominal ultrasound. Blood was centrifuged (at 1,200 x g) and sera were collected. Blood samples were analyzed for the concentration of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone using enzyme-linked immunoassay. Time to pregnancy was calculated as the number of days between when ewes were first housed with the ram until the first day of gestation. Number of fetuses was determined on between day 30 and day 40 by transabdominal ultrasound, and the number of lambs was counted after parturition. Data were analyzed using RStudio (RStudio, Boston, MA). There was no significant effect of treatment or time on concentration of FSH or LH. Additionally, there was no significant effect of time on concentration of progesterone. However, there was a tendency for the concentration of progesterone in RES to be greater than that of CON (P = 0.09). There were no significant effects from treatment on time to pregnancy, number of fetuses, or number of lambs.

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