Effects of dietary sunflower seeds on lactation performance and conjugated linoleic acid content of milk

The conjugated linoleic acid (CLA) concentration in milk and the lactation performance of cows fed either a control (CON) or a sunflower seed [SS; 7% of dietary dry matter (DM)] containing diet were compared in a 12-wk lactation trial, starting from week 3 after calving, with 17 multiparous and 8 primiparous cows. The CON and SS diets were isonitrogenous and provided 4 and 6% crude fat in the total mixed rations and were fed to 13 and 12 cows, respectively. Daily DM intake (DMI), milk production and weekly body weights were recorded. Milk samples collected weekly at four consecutive milkings were individually analyzed for fat, protein and lactose content, and fatty acid composition. The DMI and milk production of the cows fed the CON and SS diets were 20.5 +/- 0.80 and 20.2 +/- 0.80 kg d(-1) (P > 0.05) and 38.2 +/- 1.71 and 38.2 +/- 1.71 kg d(-1) (P > 0.05), respectively. No differences due to diet were observed for cow body weight, body condition score, or for content and yield of milk fat, protein and lactose. The CLA cis-9, trans-11 concentration in milk from cows fed the CON and SS diets was 3.9 and 7.9 mg g(-1) fatty acids (P < 0.01), respectively. The average CLA cis-9, trans-11 yield in milk from cows fed CON and SS diets was 5.1 +/- 0.07 and 10.9 +/- 0.07 g d-1, respectively, or 114% greater (P < 0.05) for cows fed the SS diet. The study indicates that sunflower seed inclusion at 7% of dietary DM to dairy cows increases the CLA concentration and yield in milk, without affecting DMI, milk production or composition.