Effects of feeding oilseeds rich in linoleic and linolenic fatty acids to lactating ewes on cheese yield and on fatty acid composition of milk and cheese

Forty-two crossbred ewes were used to determine effects of feeding oilseeds rich in linoleic (C18:2) and linolenic (C18:3) fatty acids on milk and cheese yield, overall composition, and fatty acid composition. Ewes were divided into three groups and assigned to one of three diets for 21 days: a control diet with no oilseed, a sunflower supplemented diet, and a flaxseed supplemented diet. During the experimental period, ewes were kept in group-pens and fed 0.7 kg of concentrate and 2.4 kg of alfalfa hay per ewe per day. Sunflower seed and flaxseed replaced 260 and 300 g/kg, respectively, of the concentrate in the control diet. The fatty acids of the control, the sunflower and the flaxseed diet were 29, 54, and 51 g/kg, respectively. Results showed that compared with the control diet, diet with flaxseed increased (P<0.05) milk yield by 8% without affecting milk total solid, fat, and protein proportions. However, the diet with sunflower seed had no effect on milk yield but reduced (P<0.05) milk total solid, fat, and protein proportions. Cheese yield was similar for ewes fed the control and flaxseed diets and higher (P<0.05) than for ewes fed the sunflower seed diet. Oilseed supplementation increased (P<0.05) concentrations of mono-unsaturated, poly-unsaturated, and long-chain fatty acids, and decreased (P<0.05) concentrations of saturated, short-chain, and medium-chain fatty acids in both milk and cheese. Concentrations of C18:3 and conjugated linoleic (CLA) acid in milk and cheese increased (P<0.05) with oilseed supplementation. Milk and cheese from ewes fed the sunflower seed diet contained more (P<0.05) CLA and less (P<0.05) C18:3 than milk and cheese from ewes fed the flaxseed diet. The increase in CLA and C18:3 in cheese from ewes fed the sunflower seed diet was 140 and 63%, respectively. The corresponding increase in cheese from ewes fed the flaxseed diet was 60 and 113%, respectively. Feeding oilseeds rich in poly-unsaturated fatty acids to lactating ewes under our experimental conditions resulted in substantial changes in milk and cheese fatty acid profiles with minimal effects on milk and cheese yields. Cheeses with specific human health-promoting fatty acids can be produced from milk of ewes by selective feeding of oilseeds.