HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) All Versions of this Article: jas.2008-1420v1 87/3/1120    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Duckett, S. K. Articles by Pavan, E. Search for Related Content PubMed PubMed Citation Articles by Duckett, S. K. Articles by Pavan, E.

Corn Oil or Corn Grain Supplementation to Steers Grazing Endophyte-Free Tall Fescue. II. Effects on subcutaneous fatty acid content and lipogenic gene expression

S. K. Duckett, S. L. Pratt and E. Pavan^*

Clemson University, Clemson, SC 29634-0311 ^* Instituto Nacional de Tecnología Agropecuaria, Balcarce, Argentina

sducket{at}clemson.edu

Abstract

Twenty-eight Angus steers (289 kg) were finished on a high concentrate diet (85% concentrate/15% roughage; C), or endophyte-free tall fescue pastures with corn grain supplement (0.52% BW; PC), corn oil plus soybean hull supplement (0.10% BW corn oil plus 0.45% BW soybean hulls; PO), or no supplement (pasture only; PA). Subcutaneous adipose tissues were processed for total cellular RNA extraction and fatty acid composition by GLC. Relative expression of genes involved in lipogenesis [fatty acid synthase (FASN), acetyl Co-A carboxylase (ACC), lipoprotein lipase (LPL), stearoyl Co-A desaturase (SCD),] and activators of transcription [peroxisome proliferators-activated receptors (PPAR), CCAAT/enhancer-binding proteins (C/EBP), sterol regulatory binding proteins (SREBP-1), STAT-5, and Spot-14] was determined by qRT-PCR. Housekeeping gene (GAPDH and β-actin) expression was used in analysis to normalize expression data. Total fatty acid content was highest (P < 0.001) for C and lowest (P < 0.001) for PA. Supplementation of grazing cattle increased (P < 0.001) total fatty acid content compared to PA but levels were lower (P < 0.001) than C. Myristic and palmitic acid contents were higher (P < 0.001) for C than PO and PC, which were higher (P < 0.001) than PA. Stearic acid content was greater (P < 0.01) for PO than C, PC and PA. Finishing on a high concentrate diet increased (P < 0.001) total MUFA content by 68% compared to PA. Corn grain supplementation increased (P < 0.001) MUFA content compared to PA; in contrast, MUFA content did not differ (P > 0.05) among PO and PA. Corn oil supplementation increased (P < 0.001) trans-11 vaccenic acid (TVA) content in s.c. fat by 1.2-, 1.7- and 5.6-fold relative to PA, PC, and C, respectively. Concentrations of CLA, cis-9 trans-11 isomer, were 54%, 58%, and 208% greater (P < 0.01) for PO than PA, PC, and C, respectively. Corn grain supplementation to grazing steers did not alter (P > 0.05) cis-9 trans-11 isomer of CLA compared to PA. Oil supplementation increased (P < 0.001) linoleic (C18:2) acid content by 56, 98 and 262% compared to C, PC and PA, respectively. Relative mRNA expression of SCD was up-regulated (P < 0.001) by 46-, 18- and 7-fold, respectively, for C, PC and PO compared to PA. Relative FASN mRNA expression was also up-regulated (P = 0.004) by 9- and 5-fold, respectively, for C, and PC compared to PA. Grain-feeding, both on a high-concentrate diet or supplemented on pasture, up-regulated FASN and SCD mRNA to increase MUFA and de novo fatty acids in s.c. adipose. Up-regulation of SCD with grain feeding but low tissue CLA levels suggest that the lower CLA levels are the result of limited substrate (TVA) availability.

Key Words: beef • supplementation • fatty acid

This article has been cited by other articles:

				E. L. Steinberg, J. W. Comerford, V. H. Baumer, and E. W. Mills Production Characteristics of Pasture-Fed Beef Professional Animal Scientist, August 1, 2009; 25(4): 443 - 448. [Abstract] [PDF]