Ok i bought several spawn eggs today, i am very new to minecraft and love it. i tried using 3 eggs in my house i right clicked the egg by itself it made the animal and the vanished from my inventory. i tried it again to see if maybe i did something wrong, with the same results. i contacted a mod and an admin and maybe it  was hard to understand what i was saying i thing a hacker had just been caught or something ,but they couldnt help me. i did gather from the admin that i couldnt use it in town so i walked out till it said i was in the wilderness and also put it in a dispenser , it made 1 animal then no more i looked in the dispenser and the egg was gone again. So it is a very good chance this is a lack of knowledge on my part thing so if anyone can tell me what went wrong i will be thankfull.