Abstract
The purpose of this study was to determine the effects of using different levels of flaxseed in dairy cattle diet on performance and milk fatty acid profile. For this purpose, 9 lactating Holstein cows of the same parity and lactation stage were used. The study followed a crossover design with three periods, three treatment groups, and three cows per group. Each period lasted 21 days, of which 14 days was the adaptation period and 7 days was the data collection period. During the experiment, 2 different concentrate feeds were used, along with corn silage, vetch hay, wet sugar beet pulp, and straw as roughages. Feeds were prepared as a total mixed ration. Cows in control, 1st and 2nd treatment groups received a diet containing 0, 250 and 500 g/d flaxseed, respectively. Adding flaxseed to the diet did not affect dry matter intake, milk yield, feed efficiency, or milk fat, lactose, and urea nitrogen (P > 0.05). However, it increased omega-3 fatty acids in milk and decreased the ratio of omega-6 to omega-3 fatty acids (P < 0.05). Results showed that adding different levels of flaxseed to the diets increased omega-3 fatty acids in milk without negatively affecting performance or fat percentages, making it suitable for producing functional milk.