Another strategy that can reduce CH4 emission is fat supplementation, and feeding fat can also modify the milk FA profile. In practice, polyunsaturated fats are fed to dairy cows to manipulate milk FA profiles, increasing the concentrations of PUFA and CLA, which have potential beneficial effects on human health (Mele, 2009). Generally, vegetable oils (e.g., soybean, canola, linseed) are used as fat supplementation, whereas the use of alternative oils rich in n-3 PUFA, such as fish oil (FO), is not very common. Fish oil is characterized by a high concentration of long-chain unsaturated fatty acids, which have been shown to decrease methanogenesis (Fievez et al., 2003).