Milk kefir grains mainly feed on ingredients found in animal milk (cow's milk, goat's milk, etc.).
For people who do not wish to consume animal milk, the use of vegetable "milk" (soy milk, almond milk, etc.) is an alternative, provided that kefir grains are regularly returned to animal milk.
Please pay attention to the fact that using only vegetable "milk" will result in the loss of grains over time because they do not find the nutrients they need.
In this picture, the milk kefir seeds are about to thicken vanilla flavored organic soy milk.
... and here, the milk kefir seeds thicken organic goat's milk.