A bottle of goat milk: an impossible prestation?

Art. 1200, par. 2, of the Civil Code says:

     The debtor shall have no right to choose those prestations which are impossible, unlawful or which could not have been the object of the obligation.

On page 267 of the Civil Code of the Philippines, Annotated, Vol. IV, 2008 Edition by Edgardo L. Paras we find his annotation on the matter:

My first impression was that Paras did not believe that goats produce milk.

On second thought I think  Paras in his time did not know of a goat that could produce a bottle of milk in one milking. Well, not today (click on the image to go to the source):

At any rate, one does not need to drink goat milk from a bottle. I have a cousin, who in our younger days in the farm, would drink goat milk right from the teats of their goats.

 Now, that might be unusual but cannot be an impossible prestation.