It is true that Germans love horses even though I would be nervous if I were Joey because Germans also like horse meat and at war there isn't lots of food.  I think that even though there is a possibility that the Germans might eat the horses Joey enjoys being looked after by the Germans. 

What judgement would you make on Albert's father drinking?  
Why do you think he wants Albert to have the farm when he is old enough?
Why do you think the army wants horses not other animals like bulls or cows?  
Under what circumstances would you sell a horse like Joey?
Based on what you know, would you sell Joey if you were Albert s father?  

I think that it is indeed true that animals reared at an early age by humans think that the human is their parent.  In fact my grannie's poodle Jessica behaves in this way.  I read a book which is similar in a way in that it is about going through hardship which forms trusting relationships.  The book is also by Michael Morpurgo and is titled the Wreck of Zanzibar.  The story is about the trust between a brother and sister formed through hardship and the joy of reunion.