The effects of extruded flaxseed supplementation to high-yielding dairy cows on milk production and milk fatty acid composition

The objectives of this study were to determine the effects of extruded flaxseed supplementation to high-yielding dairy cows on milk yield and fatty acid profile. One-hundred Israeli-Holstein dairy cows averaging 150 days in milk (DIM) were stratified into two treatment groups on the basis of milk production, DIM and parity. The treatments were: (1) control--cows were fed a lactating-cows diet; and (2) extruded flaxseed (EF)--cows were fed a lactating-cows diet which included an extruded supplement at 40g/kg dry matter (DM) that contained flaxseed and wheat bran at 700 and 300g/kg, respectively. The average daily milk yield was 2.7% higher in the EF group than in the control group (45.4 and 44.2kg/d, respectively; P<0.0001), the fat content was lower in the EF group (34.1 and 36.3g/kg, respectively; P<0.03), and fat yield was unaffected. The α-linolenic acid (ALA; C18:3 n-3) in milk fat was 3.1 times, eicosapentaenoic acid (EPA; C20:5 n-3) 2.4 times, and docosapentaenoic acid (DPA; C22:5 n-3) twice as high in the EF group as in the control group (P<0.0001). The overall n-3 fatty acids (FA) concentration and yields were 2.8 times as great in the EF group as in the control group (10.9 and 3.9g/kg and 16.7 and 6.0g/d, respectively; P<0.0001). The saturated FA (SFA) content in milk fat was 36g/kg lower in the EF group than in the control (622 and 658g/kg of FA; P<0.0001). On the average, the EF increased the proportion of mono-unsaturated FA (MUFA) by 10% and polyunsaturated FA (PUFA) by 11.8% compared with the control. The n-6:n-3 FA ratio was decreased by the EF supplementation from 11.9 in the control group to 4.2 in the EF group (P<0.0001). In conclusion, feeding an extruded supplement containing 700g/kg of EF, at a DM rate of 40g/kg, increased the milk yield and decreased the fat percentage. The n-3 FA concentration and yield in milk fat were 2.8 times as high and the n-6:n-3 ratio was 2.8 times lower in the EF group than in the controls. The SFA proportion decreased and the MUFA and PUFA proportions increased in response to EF supplementation.