Effects of Conjugated Linoleic Acid on Lipid Metabolism and Energy Balance in Dairy Cows

Persistent Link:
http://hdl.handle.net/10150/193624
Title:
Effects of Conjugated Linoleic Acid on Lipid Metabolism and Energy Balance in Dairy Cows
Author:
Kay, Jane Kirrily
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Three experiments were conducted for this dissertation with the goals to; 1) determine conjugated linoleic acid (CLA) effects on net-energy balance (EBAL) and milk production parameters during periods of nutrient/energy stress, and 2) investigate temporal CLA effects on mammary lipogenic gene expression. Study one was designed to determine if abomasal CLA infusion could reduce milk fat synthesis and partition nutrients towards alternative milk components in feed restricted rotationally grazed dairy cows. Data indicate abomasally-infusing CLA reduced milk fat synthesis in nutrient restricted grazing dairy cows and improved calculated EBAL and milk protein production. Another period of transitory stress experienced by the lactating dairy cow is immediately postpartum and study two objectives were to feed rumen inert-CLA to evoke milk fat depression (MFD) and investigate production and bioenergetic parameters. Data indicated a high CLA dose (3 x greater than needed in established lactation) inhibited milk fat synthesis immediately postpartum and improved calculated EBAL in grazing dairy cows. A curvilinear relationship existed between the severity of CLA-induced MFD and milk yield response. Moderate CLA-induced MFD (<~35%) tended to increase milk yield whereas severe MFD (>~35%) diminished this response. Previous research speculated that extensive MFD might decrease Δ⁹-desaturase (stearoyl CoA desaturase; SCD) and subsequent membrane fluidity to such an extent as to adversely affect cellular functions and inhibit milk secretion, thus decreasing milk yield. However, SCD inhibition was temporally independent in the present study, offering little support for the aforementioned theory. Mammary sensitivity to CLA increased as lactation progressed and previous speculations attributed this to reduced contribution of de novo synthesised fatty acids or increased competition from circulating non-esterified fatty acids immediately postpartum. However, data indicate that de novo fatty acids and milk fat trans-10, cis-12 CLA content don’t appreciably change during early lactation, (even though MFD became more severe) offering little support for either hypothesis. Study three investigated the effects of intravenous CLA infusion on temporal expression of mammary lipogenic genes to determine if trans-10, cis-12 CLA down regulates expression of a key gene (i.e. acetyl CoA carboxylase, ACC, the rate limiting enzyme in de novo fatty acid synthesis) and reduction in other mammary lipid synthesis genes is due to lack of substrate (i.e. malonyl CoA), or an alternative indirect mechanism. Data indicated however, that mammary lipogenic genes (ACC, fatty acid synthetase and SCD) followed a similar temporal pattern, providing more support for a global regulator (i.e. sterol regulatory element binding protein-1, peroxisome proliferator-activated receptor-γ or nuclear factor- κB) rather than a specific key enzyme effect.
Type:
text; Electronic Dissertation
Keywords:
dairy cow; conjugated linoleic acid; lactation; energy balance
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Animal Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Baumgard, Lance H.
Committee Chair:
Baumgard, Lance H.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleEffects of Conjugated Linoleic Acid on Lipid Metabolism and Energy Balance in Dairy Cowsen_US
dc.creatorKay, Jane Kirrilyen_US
dc.contributor.authorKay, Jane Kirrilyen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThree experiments were conducted for this dissertation with the goals to; 1) determine conjugated linoleic acid (CLA) effects on net-energy balance (EBAL) and milk production parameters during periods of nutrient/energy stress, and 2) investigate temporal CLA effects on mammary lipogenic gene expression. Study one was designed to determine if abomasal CLA infusion could reduce milk fat synthesis and partition nutrients towards alternative milk components in feed restricted rotationally grazed dairy cows. Data indicate abomasally-infusing CLA reduced milk fat synthesis in nutrient restricted grazing dairy cows and improved calculated EBAL and milk protein production. Another period of transitory stress experienced by the lactating dairy cow is immediately postpartum and study two objectives were to feed rumen inert-CLA to evoke milk fat depression (MFD) and investigate production and bioenergetic parameters. Data indicated a high CLA dose (3 x greater than needed in established lactation) inhibited milk fat synthesis immediately postpartum and improved calculated EBAL in grazing dairy cows. A curvilinear relationship existed between the severity of CLA-induced MFD and milk yield response. Moderate CLA-induced MFD (<~35%) tended to increase milk yield whereas severe MFD (>~35%) diminished this response. Previous research speculated that extensive MFD might decrease Δ⁹-desaturase (stearoyl CoA desaturase; SCD) and subsequent membrane fluidity to such an extent as to adversely affect cellular functions and inhibit milk secretion, thus decreasing milk yield. However, SCD inhibition was temporally independent in the present study, offering little support for the aforementioned theory. Mammary sensitivity to CLA increased as lactation progressed and previous speculations attributed this to reduced contribution of de novo synthesised fatty acids or increased competition from circulating non-esterified fatty acids immediately postpartum. However, data indicate that de novo fatty acids and milk fat trans-10, cis-12 CLA content don’t appreciably change during early lactation, (even though MFD became more severe) offering little support for either hypothesis. Study three investigated the effects of intravenous CLA infusion on temporal expression of mammary lipogenic genes to determine if trans-10, cis-12 CLA down regulates expression of a key gene (i.e. acetyl CoA carboxylase, ACC, the rate limiting enzyme in de novo fatty acid synthesis) and reduction in other mammary lipid synthesis genes is due to lack of substrate (i.e. malonyl CoA), or an alternative indirect mechanism. Data indicated however, that mammary lipogenic genes (ACC, fatty acid synthetase and SCD) followed a similar temporal pattern, providing more support for a global regulator (i.e. sterol regulatory element binding protein-1, peroxisome proliferator-activated receptor-γ or nuclear factor- κB) rather than a specific key enzyme effect.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectdairy cowen_US
dc.subjectconjugated linoleic aciden_US
dc.subjectlactationen_US
dc.subjectenergy balanceen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAnimal Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBaumgard, Lance H.en_US
dc.contributor.chairBaumgard, Lance H.en_US
dc.contributor.committeememberCollier, Roberten_US
dc.contributor.committeememberBauman, Daleen_US
dc.contributor.committeememberAllen, Ronald E.en_US
dc.contributor.committeememberDuff, Glennen_US
dc.identifier.proquest1781en_US
dc.identifier.oclc659747542en_US
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