title: A supplement containing trans-10, cis-12 conjugated linoleic acid reduces milk fat yield but does not alter organ weight or body fat deposition in lactating ewes.
abstract: Conjugated linoleic acids (CLA) have been demonstrated to be a potent inhibitor of milk fat synthesis in ruminants, but effects on carcass composition and organ weight are unknown. Our objectives in this experiment were to determine the dose response of ruminally protected CLA on the performance, organ weight, and fatty acid (FA) composition of early lactation dairy ewes. Twenty-four multiparous dairy ewes were fed a basal diet for 10 wk that was supplemented with a lipid-encapsulated CLA at 1 of 3 levels: no CLA (control, CON), low CLA (L-CLA), or high CLA (H-CLA) to supply 0, 1.5, or 3.8 g/d, respectively, of both trans-10, cis-12 and cis-9, trans-11 CLA. Dry matter intake was not affected (P > 0.05) by dietary treatment. Ewes fed H-CLA had a 13% higher milk yield compared with those receiving either CON or L-CLA. Compared with CON, milk fat yield (g/d) was 14 and 24% lower in ewes fed L-CLA or H-CLA, respectively. Supplementing ewes with CLA did not affect carcass or organ weights, carcass composition, or organ FA content. Compared with ewes receiving the CON diet, CLA supplementation had little effect on the FA composition of the Longissimus dorsi, although cis-9, trans-11 and trans-10, cis-12 CLA were increased in ewes receiving H-CLA. The current findings are consistent with the view that the energy spared by the CLA reduction in milk fat content was mainly partitioned to milk yield and there was no evidence of organ hypertrophy or liver steatosis.
authors.affiliation: Animal Science Research Centre, Harper Adams University College, Edgmond, Newport, Shropshire TF10 8NB, UK. lsinclair@harper-adams.ac.uk
authors.forename: Liam A
authors.initials: LA
authors.lastname: Sinclair
authors.forename: Weerasinghe M P B
authors.initials: WM
authors.lastname: Weerasinghe
authors.forename: Robert G
authors.initials: RG
authors.lastname: Wilkinson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: de Veth
authors.forename: Dale E
authors.initials: DE
authors.lastname: Bauman
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry / Q000254:growth & development; D000818:Animals; D050218:Body Fat Distribution / Q000662:veterinary*; D001835:Body Weight; D003612:Dairying / Q000379:methods; D004032:Diet / Q000662:veterinary*; D004041:Dietary Fats / Q000008:administration & dosage / Q000032:analysis*; D005227:Fatty Acids / Q000032:analysis; D005260:Female; D006321:Heart / Q000254:growth & development; D007536:Isomerism; D007774:Lactation; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D008168:Lung / Q000737:chemistry / Q000254:growth & development; D008321:Mammary Glands, Animal / Q000254:growth & development; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000737:chemistry / Q000254:growth & development; D009206:Myocardium / Q000737:chemistry; D009929:Organ Size; D034561:Sheep, Domestic / Q000254:growth & development*; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D044243:Linoleic Acids, Conjugated; C503589:cis-9, trans-11-conjugated linoleic acid; C496197:trans-10,cis-12-conjugated linoleic acid