nurture behavior

Question
We have 2 rescued border collies- 1 year apart - male (4mo) and female (16 mo).  The female greets the pup several times a day by forcing his mouth open and putting her entire snout into his mouth.  Is this a nurture behavior or something else?

Answer
Hi Sera

If she is regurgitating her food that is feeding behavior of a wild dog.

But it could be that the male has a bad tooth or she smells something in his mouth.

Open his mouth and do a check, count his teeth and check for abscess or rotten teeth.