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.2008-0946v1 86/12/3522    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 Google Scholar Google Scholar Articles by Aldai, N. Articles by McAllister, T. A. Search for Related Content PubMed PubMed Citation Articles by Aldai, N. Articles by McAllister, T. A.

Non-ionophore antibiotics do not affect the trans-18:1 and CLA composition in beef adipose tissue

N. Aldai^*, M. E. R. Dugan^*, J. K. G. Kramer, P. S. Mir and T. A. McAllister

^* Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C&E Trail, Lacombe, Alberta T4L 1W1 , Guelph Food Research Centre, 93 Stone Road West, Guelph, Ontario N1G 5C9 Lethbridge Research Centre, 1^st Avenue South 5403, P.O. Box 3000, Lethbridge, Alberta T1J 4B1

duganm{at}agr.gc.ca

Abstract

Common practice in North American feedlot industries is to add antibiotics to the diet to prevent disease and improve both weight gain and feed efficiency. In this study, 240 crossbred steer calves were backgrounded on a 54% silage diet for 80 d and fed a finishing diet consisting of 81% barley grain, 10% barley silage and 7.5% supplement (DM basis) with and without in-feed antibiotics for ~120 d. Calves were assigned to 1 of 5 treatments: control with no antibiotics, 11 ppm chlortetracycline, 44 ppm chlortetracycline, 44 ppm chlortetracycline plus 44 ppm sulfamethazine, and 11 ppm tylosin phosphate. A combination of GLC and Ag⁺-HPLC methods were used to analyze the fatty acid composition of brisket adipose tissue with emphasis on trans-18:1 and CLA isomers. The inclusion of non-ionophore antibiotics in the diet had little effect on the fatty acid composition except feeding either 44 ppm chlortetracycline or 11 ppm tylosin caused small increases in 9c-14:1 and 16:0 relative to control (0.26 and 0.9 g/100 g total fatty acids, respectively). In accord, profiles of trans-18:1 and CLA isomers were unchanged by antibiotics, but across treatments the predominant trans-18:1 isomer was 10t-18:1 (3.22%) at 3-times the concentration of the second most abundant isomer (11t-18:1; vaccenic acid, 1.05%). Rumenic acid (9c,11t-18:2) was the major CLA isomer at 61% of total CLA, followed by 7t,9c-18:2 at 9%. Because no other effects on fatty acid composition were evident, data for trans-18:1 and CLA were pooled across treatments to investigate possible relationships among rumen PUFA metabolites. The total trans-18:1 content in brisket adipose tissue was positively correlated to 10t-18:1 but not with 11t-18:1; whereas the total CLA was positively correlated with 9c,11t-18:2 but not 7t,9c-18:2. The 7t,9c-18:2 was, however, positively correlated to 10t-18:1 and 6t/7t/8t-18:1 but negatively correlated with rumenic acid. These metabolic interrelationships suggest the presence of bacterial populations with distinct pathways for PUFA biohydrogenation in which either 10t-18:1 or 11t-18:1 predominate. Overall, the non-ionophore antibiotics tested did not appreciably change adipose tissue composition and consequently could not be used to improve the trans-18:1 or CLA profile (i.e., increase vaccenic and rumenic acids at the expense of 10t-18:1).

Key Words: adipose tissue • antibiotics • beef • CLA • trans-18:1