They weren't put on this earth for food or clothing. They became that due to the depredations of mankind. Read Romans 8:19-22, or for a very detailed rebuke and call to repentance referencing nearly every Biblical scripture upon the matter, turn to the great 18th century Sermon 60 of John Wesley, from November 30, 1781, known as
The General Deliverance. They're giving their lives for our sustenance through no sin of their own. Don't torment them, be merciful.
So I guess that's why Jesus references the blood of the lamb so much,and what's with all those sheepherders!!