Why are there taste differences between different brands of butter?

Several factors are responsible for taste/flavor differences between brands of butter. All butters are pasteurized and churned, but these processes are different among manufactures, resulting in different flavor and texture. In addition, different ingredients in the feed that the cows consume can have an effect on the flavor of the milk. The cream that is used can have slightly different acid levels. The butter could be cultured or sour cream butter instead of sweet cream butter. Butterfat level can differ slightly by different manufacturers. There can be a difference in the natural flavor that is usually added to unsalted butter.