Milk production, milk composition, liver lipid contents and C18 fatty acid composition of milk and liver lipids in Awassi ewes fed a diet supplemented with protected cis-9, trans-11 and trans-10, cis-12 conjugated linoleic acid (CLA) isomers

The effect of a rumen protected form of a conjugated linoleic acid (pCLA) supplement containing approximately equal proportions of cis-9, trans-11 and trans-10, cis-12 isomers (11.8% and 12.1%, wt/wt as free fatty acid equivalents) on milk production, milk composition and liver lipid content; as well as the fatty acid profile of milk and liver in lactating sheep was studied. Fifty multiparous Awassi ewes were randomly divided into two equal groups after parturition and were fed a total mixed diet of corn silage, grass hay and concentrate from d 2 to 42 postpartum. Diet of ewes in the pCLA group was supplemented with 25 g/(d×ewe) of pCLA providing 2.2 g/(d×ewe) of both CLA isomers while sheep in the control group were fed an isocaloric diet supplemented with 21 g of a hydrogenated triglyceride of palm oil (HTG group). Milk yield was measured daily and milk composition was analysed on a weekly basis. Liver total lipid, triglyceride and fatty acid composition was determined from liver samples collected by percutaneous needle biopsy on d 2, d 21 and d 42 postpartum. Higher milk production (1.89±0.13 vs. 1.73±0.25 kg/d) and milk protein yield (96.2±8.7 vs. 84.9±10.2 g/d) and lower milk fat content (56.8±6.2 vs. 62.7±7.1 g/kg milk) was detected in the pCLA sheep than in the HTG group. No differences were observed in the dry matter intake, milk fat yield or milk protein concentration between the two groups. Supplementation with pCLA resulted in lower total lipid (72.6±5.6 vs. 82.0±6.0) and triglyceride (49.1±5.9 vs.60.9±5.7) concentrations in the liver samples collected d 21 postpartum than in the HTG group. The pCLA supplementation increased c9, t11 C18:2 and t10, c12 C18:2, and decreased c9 C18:1 fatty acid contents in the milk lipids. In the liver lipids pCLA supplementation resulted in higher proportions of C18:0, c9, t11 C18:2 and t10, c12 C18:2 fatty acids and lower c9 C18:1 comparing to HTG. We concluded that pCLA supplementation, containing t10, c12 isomer could decrease the risk of lipid accumulation in the liver of high-lactating dairy ewes in the postpartum period. The other isomer of pCLA increased the c9, t11 CLA content of milk lipids, which may have favourable health effects for humans consuming sheep milk or milk products.