Who is the main target of Ma Shi's poem?

Taking horses as the object.

"Horse Poems" is a set of twenty-three five-character quatrains composed by the poet Li He of the mid-Tang Dynasty. By chanting horses, praising horses, or lamenting the fate of horses, poems express the heroes' extraordinary talents, lofty ambitions, and untimely emotions and resentment. The method of expression is analogous.