Can the object parenting be animated? How to link an object to hand in DAZ3D?

I need to create a simple scene. A cow is at a table. The waitress come in. She leave a big glass on the table. Meanwhile the waitress leave the scene the cow take the glass and wait for more. 
So the problem is that when I go to the keyframe 20 and parent the glass to the cow's hand... the glass is parenting from the keyframe 0.

Or for example... How can animate a male character giving a flower to a female character? I mean start whith the flower parented to the man hand... and in x frame the flower be linked to the female hand? Is these posible?

THANKS IN ADVANCE!