Effect of fish oil and sunflower oil supplementation on milk conjugated linoleic acid content for grazing dairy cows

The objective of this study was to determine the effect of adding fish oil (FO) and sunflower oil (SFO) to grazing dairy cows' diets on the temporal changes in milk conjugated linoleic acid (cis-9, trans-11 CLA). Sixteen Holstein cows were divided into two diet regimen groups. One group (CONT) was fed a basal diet (7.6 kg DM basis) plus 400 g animal fat. The other group (FOSFO) were fed a basal diet plus 100 g of FO and 300 g of SFO (FOSFO). The cows were milked twice a day and milk samples were collected every 3-day for a period of 21 days. Both groups grazed together on pasture ad libitum and fed treatment diets after the morning and afternoon milking. Milk production, milk fat percentages, milk fat yield, milk protein percentages, and milk protein yield were not affected (P>0.05) by treatment diets. The concentrations of cis-9 trans- I I CLA and vaccenic acid (VA) in milk fat were higher (P<0.05) for cows fed the FOSFO over 3 week of lipid supplementation. The concentration of cis-9 trans- 11 CLA in milk fat reached maximum on day 3 with both diets and remained relatively constant thereafter. The concentration of VA in milk fat followed the same pattern of temporal changes as cis-9 trans- 11 CLA. In conclusion, milk cis-9, trans- 11 CLA and VA concentrations increased with FO and SFO supplementation compared with the CONT diet and the increase reached a plateau on day 3 of supplementation and remained relatively constant throughout the remainder of the study. (C) 2007 Elsevier B.V. All rights reserved.