Use of ‘has had’ and ‘had’

Why do we use ‘has had’ here rather than just ‘had’? Which of the following sentences do you think makes more sense?

My giraffe had an operation, and now must wear some protection.
My giraffe has had an operation, and now must wear some protection.

Actually they both work equally well in this case, but only because we have added more information about the time of this event (now). Without this time information, the statements would be ambiguous:

My giraffe had an operation
– when was this, recently or years ago?

My giraffe has had an operation
– implies that the operation was recent.