title: Effect of feeding rumen-protected conjugated linoleic acid on carcass characteristics and fatty acid composition of sheep tissues.
abstract: Two experiments were conducted to determine the effectiveness of a rumen-protected CLA (pCLA) supplement and the impact of feeding this pCLA on carcass characteristics and tissue fatty acid composition of lambs. In Exp. 1, a CLA-80 preparation (80% pure CLA; contained similar proportions of cis-9, trans-11, and trans-10, cis-12 CLA), protected against rumen degradation, was fed to sheep, and the proportion of CLA reaching the duodenum was determined. A 3 x 3 Latin square design was used with 3 diets (1.4 kg of concentrate-based control diet, the same control diet plus 22 g of CLA-80, or the same control diet plus 110 g of pCLA/d), 3 feeding periods, and 3 rumen and duodenally cannulated sheep (Mule x Charolais males, 10 mo of age, BW 55.3 +/- 1.8 kg). After 7 d of feeding, sheep were ruminally infused with chromium EDTA and Yb acetate for 7 d, after which samples of duodenal digesta were collected every 6 h for 48 h to determine the quantity of CLA reaching the small intestine each day. The amounts of CLA cis-9, trans-11 and trans-10, cis-12, and combined isomers, flowing through the duodenum each day were greater (P = 0.01) in sheep fed pCLA. Approximately 65% of the pCLA avoided rumen biohydrogenation, with the ratio of the 2 main isomers remaining similar. In Exp. 2, 36 Mule x Charolais ewe lambs (approximately 13-wk old, average initial BW 29.3 kg) were fed 3 levels of the pCLA or Megalac, which were fed to provide an equivalent energy content at each pCLA level. Lambs were randomly assigned to 1 of 7 treatment groups, which were fed for 10 wk to achieve a growth rate of 180 g/d. Treatments included the basal diet and the basal diet plus 25, 50, or 100 g of pCLA/kg of diet or the equivalent amount of Megalac. In liver (P < 0.001) and all adipose tissue depots studied, the proportions of both CLA isomers increased (P = 0.02) with the amount of pCLA fed but were not altered with increasing of Megalac. Although there was no effect of treatment on cis-9, trans-11 CLA content, accumulation (P < 0.001) in the LM with increasing of pCLA supplementation was observed for the trans-10, cis-12 isomer. Although tissues had been enriched with CLA, there was no evidence of a reduction in adipose tissue or an increase in muscle mass in these sheep. However, an effect of pCLA on tissue fatty acid composition was consistent with an inhibition of stearoyl-CoA desaturase.
authors.affiliation: Division of Nutritional Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Wynn
authors.forename: Z C T R
authors.initials: ZC
authors.lastname: Daniel
authors.forename: C L
authors.initials: CL
authors.lastname: Flux
authors.forename: J
authors.initials: J
authors.lastname: Craigon
authors.forename: A M
authors.initials: AM
authors.lastname: Salter
authors.forename: P J
authors.initials: PJ
authors.lastname: Buttery
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats; D004304:Dosage Forms; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D012756:Sheep / Q000502:physiology*; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D004304:Dosage Forms; D005227:Fatty Acids; D044243:Linoleic Acids, Conjugated; D012333:RNA, Messenger; D013230:Stearoyl-CoA Desaturase; D000103:Acetyl-CoA Carboxylase