This thread is from 2013, you're not likely to recieve a reply from the op.
What's a Spooner? Chickens don't really graze, they can't digest grass like a cow or goat.
Is that a vaccine brand?
What goals do you have for your flock to need it?
Unfortunately, mareks vaccines only prevent *for the most part* the deadly tumors from growing, they can still catch, spread and die from the disease.
Really hot, really cold, clouds (light controls hormone production), molting, noise and predators can all make hens not lay. But not feed unless they're getting nutritionally deficit feed i.e nothing but corn.
I have 16 hens, all are old enough to lay, but I'm only getting 3 eggs a day. It's...