Transfer of conjugated linoleic acids into different tissues of dairy cows

The objective of this study was to investigate the transfer of supplemented trans-10,cis-12 (t10,c12) and cis-9, trans-11 (c9,t11) conjugated linoleic acids (CLA) into the body of dairy cows during the first 105 days in milk (DIM). Therefore, five out of 25 first lactation German Holstein cows were slaughtered at 1 DIM without previous CLA or fat supplementation. The remaining animals received daily 6.0 g t10,c12 CLA and 5.7 g c9,t11 CLA as feed supplement (Group CLA, 10 cows) or a stearic acid-based control fat supplement (Group CON, 10 cows). From both groups, five cows were slaughtered at 42 and 105 DIM, respectively. During the slaughter process, the empty body mass of the cow was partitioned into nine fractions (retroperitoneal fat, omental fat, mesenteric fat, subcutaneous fat, meat, bone, offal, hide and mammary gland). The fat content and the fatty acid composition of these fractions were determined. The c9,t11 CLA isomer was detected in all fractions across all groups, but the amount of c9,t11 CLA was not changed because of CLA supplementation. Except for the retroperitonealfat depot, no t10,c12 CLA was detected in the fractions of Group CON. After CLA supplementation, the amount of t10,c12 CLA in the retroperitoneal, mesenteric, subcutaneous, offal and mammary gland fractions was increased. The transfer of t10,c12 CLA into the fractions was more pronounced from 42 until 105 DIM. However, the transfer efficiency of consumed t10,c12 CLA into the fat depot fractions and all fractions was <0.1% and <0.2%, respectively. Overall, the transfer of supplemented CLA isomers into the dairy cow's body was only marginal during the first 105 DIM.