Vladi, I cannot believe that you are required to turn these active sentences into the passive voice-- they are incredibly awkward and would never appear in the natural language.
1. Practically all spaniels have an affectionate disposition.
1a. An affectionate disposition is had by practically all spaniels.
2. All dogs of this breed have pendant ears.
2a. Pendant ears are had by all dogs of this breed.
3. The cocker spaniel usually has a silky coat.
3a. A silky coat is usually had by the cocker spaniel.