Stearic acid does not overcome conjugated linoleic acid trans-10, cis-12-induced milk fat depression in lactating ewes

Abstract

The objective of this study was to test the hypothesis that stearic acid supplementation increases milk fat content and overcomes the antilipogenic effects of trans-10, cis-12 conjugated linoleic acid (CLA) in lactating ewes. Twenty-eight Lacaune ewes (36 ± 2 DIM; 70.5 ± 9.6 kg BW), producing 1.8 ± 0.4 kg of milk/day were used in a completely randomized design (7 ewes/treatment) for 21 days. The treatments were: 1) Control; 2) CLA (6.4 g/day of trans-10, cis-12 CLA); 3) SA (28 g/day of stearic acid) and; 4) CLASA (6.4 g/day of trans-10, cis-12 CLA plus 28 g/day of stearic acid). All data were analyzed using a mixed model that included the fixed effect of treatment and the random effect of ewe. SA did not alter milk fat content and yield relative to Control (91.9 vs. 91.2 ± 4.1 g/d). SA in association with trans-10, cis-12 CLA (CLASA) was not able to overcome the reduction in fat content and fat yield induced by CLA (75 vs. 82 ± 0.14 g/d). SA increased the relative abundance of CD36, FABP4 and PPAR-γ mRNA by 140%, 112% and 68% compared to CLASA. SA also reduced the relative abundance of ACACAα PII and SCD when compared to Control (45% and 39%). Compared to CLA, CLASA treatment had no effect on the mRNA abundance of FASN, LPL, CD36, SCD, FABP4, AGPAT6, SREBP1 and PPAR-γ. In conclusion, stearic acid supplementation did not increase milk fat synthesis and did not overcome the CLA-induced milk fat depression when associated with trans-10, cis-12 CLA.