Enhancing unsaturated fatty acids in ewe's milk by feeding rapeseed or linseed oil

The aim of our research was to evaluate whether rapeseed and linseed oils used as feed additives to ewe's diets allow to achieve the higher secretion of unsaturated fatty acids into milk with extended emphasis on the conjugated linoleic acid concentration. Two experiments were carried out on 6 lactating ewes in two independent 3 × 3 Latin square designs. In each feeding cycle the animals were subjected to one of the treatments: (1) without oil supplementation, (2) with 3.5% of rapeseed oil (RS) or linseed oil (LS), (3) with 7.0% of rapeseed oil or linseed oil. Feeding diets rich in mono- and polyunsaturated fatty acids to lactating ewes under our experimental conditions resulted in demanded changes in milk fatty acid content without causing milk fat depression or modification of other milk constituents. Milk fat was improved in unsaturated fatty acids including C18:2 c9 t11 CLA isomer without changing the milk fat concentration. The C18:2 c9 t11 concentration increased from 0.03 (FAME, %) in the control group to 0.21 and 0.12 (FAME, %) in groups receiving 3.5 and 7% RS, respectively. The diet with 7% LS also elevated the C18:2 c9 t11 level in milk from 0.04 (FAME, %) in the control group to 0.11 (FAME, %). Hence a conclusion is drawn that plant oils may be an important source of monoenic and also polyenic fatty acids in milk, however, our research and analysis of literature data indicate that results are strictly dietary and supplement-dependent.