Praise be to Allaah.
With regard to the ruling on his urine in the first two
years changing in the case of his being fed with milk other than that of
his mother, that is a matter concerning which there are differences of
opinion. The most likely to be correct - and Allah knows best - is that he
is like the one who is breastfed by his mother, and it cannot be said that
he is being given solid food. If he is being given artificial milk in
place of his mother’s milk, the most correct view - and Allah knows best -
is that it is sufficient to sprinkle water over his urine, like the one
who is being nourished by his mother’s milk. This is what is most likely
to be the correct view. And Allah knows best. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)
Fataawa Noor ‘ala al-Darb (2/660).