It is quit ethical and right to raise animals for humans consumptions i will list and explain some of the points below but first of all i will like you to know am a graduate of agriculture from a reputable University in Nigeria FUTMINNA.

Hunting can no longer meets the protein demand of man.

From the beginning man has being feeding on animal but majorly by hunting this animals gradually the animals are going into extinction and also improving in techniques to escape man thus the introduction of what is called livestock farming.
Man no longer need to hunt before he can put meat on his table all he needs do is to buy from a seller. Even the animals in the wilds now have more freedom from the constant attack by man. Now man can rear goat, cattle,birds ,pigs, fish and many other terrestrial and aquatic animals without disturbing the peace of the animals in the wilds.

High-protein, low-carbohydrate diets are the hottest thing since sliced flank steak, and every food marketer in the known universe appears to want a piece of the protein pie.
Body builders are snatching, grabbing, and gulping down protein shakes. Dieters are gobbling down protein bars (and shunning pasta) in hopes of quick weight loss.

The above comment shows the unquestionable high demand of protein which can only be met by rearing of animals for mans consumption.

Is it ethical ?

In the beginning when God created man he said

And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth. Gen 1:28

I quit agree that it is ethical and lawful to rear animal for human consumption.