Ruling on urine of a nursing infant who is fed artificial milk
Question

If an infant is fed with artificial milk in the first two years, is he regarded as having been weaned, and does that change the ruling on his najaasah?.
Praise be to Allah.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)