Effect of including canola oil in dairy cows diets on the milk yield and milk fatty acids profile.

A total of 18 lactating dairy cows were assigned to three groups: control group C (no dietary oils), group CO (with dietary canola oil) and group FO (with dietary flax seeds oil). All three groups received corn silage (ad libitum), alfalfa hay (limited to 4 kg/day) and compound feeds (limited to 6.5 kg/day). The inclusion rate of the two dietary oils was 10.4% in the compound feed or 3.8% on a dry matter basis, so that the cows consumed 600 g daily. The monitored experimental parameters were: diet formulation and composition, dietary supply of energy and protein, feed intake, milk yield and composition, milk fat fatty acids profile. The total intake of dry matter, milk yield, the production of milk protein and milk protein didn’t differ significantly among the experimental groups, or among them and the control group. On the other hand, milk fat and the production of milk fat were very different (P<0.05). The following trends were noticed concerning the milk FA profile: decrease of C 16:0 (P<0.01) and C 16:1 (P<0.05), increase of C 18:0, C 18:1 n-9 trans (P<0.05), C18:1 n-9 cis (P< 0.01), C 18:3 n-3 (P<0.001), and the stable level of C 18:2 n-6 trans, C 18:2 n-6 cis and C 18:3 n-6. Compared to the canola oil, the flax seeds oil diet resulted in a lower level of C 18:1 n-9 cis (P<0.01) in the milk fat and in a higher level of C 18:3 n-3 (P<0,001). The highest level of milk fat PUFA resulted from the use of the dietary flax seeds oil, both compared to the diets with canola oil and compared to the control diet (P<0,01).