My girl also drink less milk when she turned 1. At first I also feel frustrated coz I feel like it's a routine for her 3-4 hourly milk time. So I switched to different brand. Now she's 16 mths. Drinks milk 4 times a day. Beside that, she eats solid food. Used to drink One Nature Dairy but now she drinks Dumex Mamil Gold 3.
For 1 yr old, he should be eating more than drinking milk. He can start drinking fresh milk already. Try to change & see if he likes it or not.
Just a Mummy