Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Jeffrey A. Clapper

Keywords

gilt, hypothalamus, Kisspeptin, Kisspeptin receptor, pig, pituitary

Abstract

Kisspeptin has been demonstrated to affect reproductive cyclicity and the attainment of puberty in multiple species, presumably through its actions on GnRH and LH, as demonstrated in other species. Kisspeptin administration causes increased plasma concentrations of LH in pigs, sheep, and rats. Two experiments were conducted to evaluate 1) the hypothalamic kisspeptin system throughout various days of the estrous cycle and 2) the hypothalamic kisspeptin system during the peripubertal period in gilts. In experiment 1, 40 crossbred gilts (191 d, 121 kg) were administered an intramuscular injection of PG600. Twelve days after the administration of PG600, gilts were fed 15 mg of altrenogest daily for 15 d to synchronize estrus. Following estrus synchronization, estrus detection was performed by exposing gilts to a mature boar and the first day gilts stood immobile was denoted d 1 of the estrous cycle. Blood samples were collected via jugular venipuncture on d 1, 4, 7, 9, 14, 16, and 19 of the estrous cycle. Ten animals were slaughtered on d 1, 9, 14, and 21 of the estrous cycle when MBH, AP, and blood were collected. Relative expression of hypothalamic Kiss1, Kiss1R, ER-alpha, ER-beta and beta-actin was determined using real-time reverse transcriptase PCR. Fold changes in relative expression were determined using the Relative Expression Software Tool. Relative expression of Kiss1 was increased (P=0.006) 3.2 fold on d 1 versus d 21 and (P=0.003) 2.3 fold on d 9 versus d 21 of the estrous cycle. Relative expression of Kiss1 was not different (P>0.05) among the remaining days. Relative expression of ER-beta was decreased (P=0.05) 0.8 fold on d 9 versus d 21 and (P=0.005) 0.7 fold on d 14 versus d 21. Relative expression of ER-beta was not different (P>0.05) among the remaining days. Relative expression of Kiss1R and ER-alpha were each not different (P>0.05) among days. In experiment 2, two studies were performed, each with 25 crossbred gilts (151 d, 105 kg). In study 1 gilts were slaughtered on d 7 and in study 2 gilts were slaughtered on d 8. Gilts were relocated and exposed to a mature boar throughout study to naturally induce puberty. Gilts that stood immobile within 24 hours of slaughter were considered to have attained puberty (n=8/study). Plasma samples were collected on d 1, 3, and 7 of the first study and d 2, 4, 6, and 8 of the second study. When gilts were slaughtered in both studies, MBH, AP, and blood were collected. Relative expression of MBH Kiss1 and beta-actin and AP GnRHR, LH-beta, and beta-actin was determined using real-time reverse transcriptase PCR. Fold changes in relative expression were determined using the Relative Expression Software Tool. Hypothalamic and AP content of kisspeptin were determined by RIA and differences were determined using the GLIMMIX procedure of SAS. Relative expression of Kiss1 was increased (P=0.005) 2.2 fold in the gilts that had attained puberty in the first study, however, was not different (P=0.16) when comparing treatments in the second study. Relative expression of GnRHR was not different (P>0.05) between treatments in both studies. Relative expression of LH-beta tended to be decreased (P=0.09) 0.80 fold in the first study but was not different (P=0.19) in gilts that attained puberty in the second study. AP concentrations of LH were not different (P=0.35) between treatments in the first study and were decreased (P=0.01) in gilts that attained puberty in the second study. AP concentrations of kisspeptin were not different (P=0.43) in the first study but were increased (P=0.04) in gilts that had attained puberty in the second study. MBH concentrations of kisspeptin were increased (P=0.03) in gilts that had attained puberty in the first study but were not different (P=0.68) between treatments in the second study. These data further support the notion that MBH expression of Kiss1 and concentrations of kisspeptin and AP concentrations of kisspeptin influence reproductive cyclycity and the attainment of puberty in the gilt.

Library of Congress Subject Headings

Sows -- Physiology

Sows -- Development

Estrus

Kisspeptin

Description

Includes bibliographical references (page 84-98)

Format

application/pdf

Number of Pages

114

Publisher

South Dakota State University

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Rights Statement

In Copyright