Document Type

Thesis - Open Access

Award Date

2017

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

George A. Perry

Second Advisor

Julie A. Walker

Abstract

Nutritional changes immediately after insemination can result in increased embryonic mortality, but the mechanisms that cause this increased mortality and the impact on the embryos that survive are not known. Therefore, two experiments were conducted to evaluate the impact of a nutritional change immediately following AI on calf performance, global DNA methylation, estrus expression and interval to estrus in heifers, peripheral metabolites, uterine luminal fluid metabolites, and day 6 embryo quality. In the first study (chapter 2) Angus-cross heifers (n = 142) were allotted into two developmental treatments: drylot or range. All heifers were fixed-time inseminated to a single sire each year and were turned out to pasture together and managed as a single group. Pregnancy success to AI was determined via ultrasonography, and calving data (calving date, birth weight, sex, and weaning weight) were collected. Samples of DNA were obtained from calves at weaning and analyzed for global methylation (total methylation and 5-hmC methylation). Results from this study indicate that heifer development and sire can impact future performance of the calf that is in utero as determined by BW and WW, and this change in performance may be regulated through DNA methylation. In the second study (chapter 3) Angus-cross heifers (n = 60) were allotted into two pre-AI treatments: low or high. Low treatment heifers were limit-fed ground cornstalks and mineralized soybean meal and urea to achieve 64.1% maintenance. High treatment heifers had ad libitum access to ground cornstalks and supplemented mineralized soybean meal, urea, and corn to achieve 139% maintenance. Heifers remained in their respective treatments for 33 to 36 days and were then inseminated upon estrus expression from a single collection of a single beef sire. Following AI, 30 heifers were randomly reassigned within treatment, creating four nutritional treatments: low treatment remaining on low (LL), low treatment moving to high (LH), high treatment remaining on high (HH), and high treatment moving to low (HL). Heifers remained on treatments post-AI for six days and were then flushed for embryo and uterine luminal fluid (ULF) collection. Blood samples were collected daily from AI to embryo collection. Results from this study indicate that the early stages of embryo development are sensitive to maternal plane of nutrition even though ULF metabolite concentrations are not representative of peripheral metabolite concentrations during the first six days of gestation. Therefore, proper nutritional management is critical around the time of AI to ensure heifers are not placed in a negative energy balance nor adversely impacting embryo survival and early conceptus development. Breeding season pregnancy success of heifers after this study was impacted by nutritional treatments from the study’s feeding trial. Although heifers were fed at a positive plane of nutrition for 30 days after the study prior to AI and throughout the breeding season, nutrient restriction of heifers six days after AI may be equally as detrimental in pregnancy success compared to 33-36 days of nutrient restriction prior to AI. In summary, nutritional management of heifers prior to and immediately following AI has the potential to impact embryo development and the critical window of DNA methylation, which may mediate future impacts on post-natal development of the offspring.

Library of Congress Subject Headings

Heifers -- Nutrition.
Cattle -- Embryos.
Calves -- Development.

Description

Includes bibliographical references (pages 136-153)

Format

application/pdf

Number of Pages

169

Publisher

South Dakota State University

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Rights Statement

In Copyright