Two experiments were carried out to evaluate the bio-hydrogenation of fish oil (FO) and combination with soybean oil (SBO) on fistulated dry cows. The experiment 1, was assigned treatments as follows; control, SBO, FO and SBO+FO (1:1); using 4×4 Latin square design. Results showed that FO and SBO+FO decreased C18:0 when compared to control and SBO. However, the SBO+FO group had the greater t11-C18:1 after feeding. Supplemented FO were reduced ruminal pH and acetic acid at 2 hrs, while the ammonia-N (NH3-N) was increased all times after feeding. The experiment 2, was supplementation of FO + SBO at ratios 2:1, 1:1 and 1:2; using 3×3 Latin square design. Results showed that SBO+FO (2:1) had high proportion of t11- C18:1 than 1:1 and 1:2 ratios. Moreover, increasing the proportion of FO in the combination oils can increased NH3-N at 2 hrs and propionic acid at 4 and 6 hrs.
