This is a situational question and is asking you to consider the most appropriate course of action. It is important prior to your interview that you research into some common veterinary situations in case you are presented with such a question. The interviewer is looking to assess your knowledge and understanding of the role.
"If the dog is unable to feed all of her puppies it would be essential for the vet to step in and provide assistance to prevent the puppies from undernourishment. Any puppies that appear restless and do not have fat tummies will benefit from supplemental feeding 1-3 times a day"