Milk of kosher animals is kosher. And goats are kosher. To ensure that the milk in your cup comes from only kosher animals (in this case goats), Jewish law requires that a mashgiach (Jewish supervisor) be present for the duration of the milking process. Where supervised milk is unavailable, some rabbinic authorities permit government inspection as sufficient assurance (although not in all countries). In common parlance, this is known as chalav stam. All agree, however, that actual supervision is preferable. Milk with such supervision is known as chalav Yisrael.

Even when chalav Yisrael is very difficult to obtain, many people go out of their way to acquire these products. Certainly, where they are readily available, one is required to use this milk.

In most of the United States, there does not appear to be commercially available chalav Yisrael goat milk. However, other goat products such as feta cheese are available in grocery stores with a sizeable kosher section.

Note: according to Jewish law, milk and meat must be kept separate and are prepared and served on separate sets of pots and dishes.