Two experiments were conducted to investigate the effects of grain source and dietary oil supplement (in experiment 1), and also effects of changing barley to corn grain ratio in an oil mixture supplemented diets (in experiment 2) on intake, feeding and chewing behavior, and milk fatty acid profile of Holstein cows using replicated Latin square design. In experiment 1, diets contained either barley or corn supplemented with either fish- or soybean-oil at 2% of dietary dry matter (DM). In experiment 2, diets contained barley, corn, and or their equal blend supplemented with fish and soybean oils mixture (1:5 ratio) at 2% of dietary DM. Changing diet fermentability did not affect both meal pattern and DM intake and thereby milk yield and milk composition were not affected by the source of grain. Barley-based diets required longer rumination times than did corn, which was a result of more rumination periods of longer duration. Regardless of grain source, the decrease in feed intake from fish oil vs. soybean oil was through reduced meal size and increased plasma malondialdehyde. Proportions of milk rumenic acid and odd- and branched-chain fatty acids in both experiments were greater in corn- and barley-based diets, respectively.
