What are the themes in Black Beauty? (Are they war, love, any thing like that?)

Anna Sewell wrote Black Beauty with the express purpose of informing readers about the themes of mistreatment of horses and of proper care of horses. 

• Mistreatment of horses

With the express purpose of informing her readers of the cruelty of the bearing rein, Sewell exemplifies the importance that the wealthy put upon the showiness of their carriage horses. In an effort to force their horses to hold their heads in a graceful position, horses were made to wear bearing reins. In the narrative, for instance, Ginger tells Beauty that she was made to wear one of these reins and two sharp bits, very painful devices because the bits cut into her mouth, while the bearing rein forced her to hold her head up all the time.

Another illustration of mistreatment of horses occurs in the narratives about the cab horses, those that pull heavy loads, and the military horses. In Chapter 35, for instance, Old Captain relates how he felt absolute terror in the midst of battle as a cavalry horse, especially when his master is killed.

"Some of the horses had been so badly wounded that they could scarcely move from the loss of blood; other noble creatures were trying on three legs to drag themselves along; and others were struggling to rise on their forefeet, when their hind legs had been shattered by shot. Their groans were piteous to hear...I shall never forget."

Perhaps the most poignant illustration of the cruelty to these working horses occurs in the later part of the novel as Beauty sees a horse being flogged for having fallen with a heavy load and was down. It was Ginger, and she died pitifully in the road. 

• Proper care of horses

Sewell's episodes about Joe Green, the young stable boy who is ignorant of the proper care of horses, nearly kills Beauty one night when he returns from having had to race a long distance with Dr. White on an emergency call. Because John is out of town, young Joe is left to take care of Beauty. He rubs the horse down, but does not cover him with his blanket. Then, out of his innocence, he gives Beauty corn to eat and cold water to drink. As a result, Beauty becomes sick with fever and inflammation in her lungs. However, she does recover. When John returns, he feels badly that he was not present to care for Beauty, and that ignorance of horse care--in a quotation combining both themes--"is the worst thing in the world, next to wickedness."