Dietary manipulations to increase the concentration of conjugated linoleic acid in milk

Ten Holstein cows between 8 and 12 weeks in lactation were used to investigate the effect of feeding full-fat soybean, full-fat sunflower, and a Ca-soap source (Profat) on the conjugated linoleic acid (CLA) content of milk. Cows were fed the experimental fat sources in the dosage of 500 g crude fat daily. The results indicated that milk CLA content increased in relation to the linoleic acid concentration of experimental fat supplements, namely full-fat sunflower increased the most and Profat increased the least the CLA concentration in milk. The strength of the correlation was r=0.62 between the linoleic acid concentration in feed and the CLA content in milk. The strength of correlation increased to r=0.69 when both linoleic acid and linolenic acid concentration of feed were used in the calculation. Considering milk production and the daily production of CLA in milk, the following equation described the relationship between the linoleic acid content of fat supplements and CLA concentration in milk: x=167.52+0.483×y; where x=CLA mg l−1 milk and y=linoleic+linolenic acid content of fat sources, g/day. Along with milk CLA, the trans-C18:1 concentration of milk also increased, but the magnitude of the increase was smaller compared to that of milk CLA