I found it easy
主 谓 形式宾语 宾补
to call pigs,tell the dogs to round up the cows,and vent my feelings to Fanny,the horse
真正的宾语（马的名字叫Fanny）
whose big brown eyes and lifted ears seemed to express interest in all I said.
定语从句（修饰马）the horse 和Fanny是什么关系，同位语吗当然