Effect of feeding extruded flaxseed on milk quality of dairy cows

Aim of the present study was to evaluate the effect of feeding dairy cows with extruded flaxseed (EF) on milk quality. After a 7-d adaptation period, 40 Holstein dairy cows in midlactation were divided in two experimental groups, based on parity, milk yield and composition, and days in milk. Animals were fed for 28 d a standard total mixed ration containing or not (control) 1.8 kg/cow/d of a supplement based on extruded flaxseed (EF). Milk yield was recorded daily and individual milk samples were collected weekly for analysis. Milk yield was not affected by treatment and averaged 26.2 kg/d throughout the study. Feeding EF reduced milk fat (3.95 vs. 4.24%; P=0.053) and tended to reduce milk protein (3.32 vs. 3.50%; P=0.104). The milk from cows fed EF contained more (P<0.01) stearic (12.0 vs. 7.8 mg/100 mg of fat), oleic (21.2 vs. 18.0 mg/100 mg of fat), α-linolenic (0.85 vs. 0.41 mg/100 mg of fat) and vaccenic (1.43 vs. 0.62 mg/100 mg of fat) acids than control and also more c9,t11 CLA (0.91 vs. 0.59 mg/100 mg of fat). Conversely, compared with control, feeding EF reduced milk concentrations of palmitic acid (26.5 vs. 33.4 mg/100 mg of fat; P<0.01). The present results show that feeding EF to dairy cows is an efficient strategy to enrich milk in beneficial fatty acids such as vaccenic acid, CLA and omega-3 fatty acids. Nevertheless, the milk fat reducing effect of flaxseed as well as other sources of polyunsaturated fatty acids should be taken into account.