I would be very very careful with introducing dairy that early... My children's father has asthma and his family have a long history of asthma, eczema & other allergies. There is a very strong connection between the early introduction of dairy and allergies...

Yoghurt is a little different in structure to cheese, milk etc so therefore is safer to introduce earlier.

Remember that baby humans are best with human milk and baby cows with cows milk. So it's harder work on their little bodies to digest something that comes from a different source...