Digital Repository at the University of Maryland (DRUM)  >
Theses and Dissertations from UMD  >
UMD Theses and Dissertations 

Please use this identifier to cite or link to this item: http://hdl.handle.net/1903/12306

Title: Denovo synthesized fatty acids as regulators of milk fat synthesis
Authors: Vyas, Diwakar
Advisors: Erdman, Richard A
Department/Program: Animal Sciences
Type: Dissertation
Sponsors: Digital Repository at the University of Maryland
University of Maryland (College Park, Md.)
Subjects: Animal sciences
Biochemistry
Nutrition
Keywords: Conjugated linoleic acid
Dairy
Fatty acids
Lipid
Mammary
Milk fat
Issue Date: 2011
Abstract: The objectives of the dissertation research were to determine the role of <italic>denovo</italic> synthesized fatty acids (DNFA) in the regulation of milk fat synthesis. Milk fat responses to increasing amounts of short- and medium-chain fatty acids (SMCFA), added in the proportion as synthesized <italic>denovo</italic>, were studied in lactating dairy cows. The results showed a significant linear increase in milk fat concentration with SMCFA supplementation. However, milk fat yield was similar for all treatments. A subsequent study was aimed at increasing the availability of SMCFA during <italic>trans</italic>-10, <italic>cis</italic>-12 CLA-induced milk fat depression (MFD) in lactating dairy cows to determine whether SMCFA can rescue part of CLA-induced MFD. Post-ruminal infusion of butterfat (BF) was used as a source of SMCFA. The BF treatment was compared to a mixture of fats containing only the long-chain FA (LCFA) with or without <italic>trans</italic>-10, <italic>cis</italic>-12 CLA infusion. Milk fat content and yield were significantly reduced with <italic>trans</italic>-10, <italic>cis</italic>-12 CLA. However, increased availability of SMCFA with BF infusion had no effects on milk fat yield and concentration. <italic>Trans</italic>-10, <italic>cis</italic>-12 CLA significantly reduced the mRNA expression of transcription factor <italic>SREBP-1c</italic> along with its downstream targets including <italic>ACC</italic>,<italic>FASN</italic>, <italic>LPL</italic>, <italic>SCD</italic> and <italic>AGPAT</italic>. The increased availability of SMCFA had no effect on either lipogenic gene or protein expression suggesting that nutritional manipulation was not sufficient to rescue <italic>trans</italic>-10, <italic>cis</italic>-12 CLA-induced MFD. Finally, the effects of combination of a Rosiglitazone (ROSI), a <italic>PPAR-&#947;</italic> agonist, and <italic>trans</italic>-10, <italic>cis</italic>-12 CLA were examined on mammary and hepatic lipogenesis in lactating mice. Mammary lipogenesis was significantly reduced with <italic>trans</italic>-10, <italic>cis</italic>-12 CLA, reducing the milk fat content and mRNA expression of lipogenic transcription factors <italic>SREBP1-c</italic> and <italic>PPAR- &#947;</italic>. <italic>Trans</italic>-10, <italic>cis</italic>-12 CLA significantly increased hepatic lipid accumulation, while the mRNA expression of <italic>SREBP1-c</italic> and <italic>PPAR- &#947;</italic> were not altered. On the contrary, ROSI had no effects on mammary lipogenesis. However, ROSI significantly rescued <italic>trans</italic>-10, <italic>cis</italic>-12 CLA-induced hepatic steatosis.
URI: http://hdl.handle.net/1903/12306
Appears in Collections:UMD Theses and Dissertations
Animal & Avian Sciences Theses and Dissertations

Files in This Item:

File Description SizeFormatNo. of Downloads
Vyas_umd_0117E_12753.pdf3.08 MBAdobe PDF417View/Open

All items in DRUM are protected by copyright, with all rights reserved.

 

DRUM is brought to you by the University of Maryland Libraries
University of Maryland, College Park, MD 20742-7011 (301)314-1328.
Please send us your comments