You can tell so much by poop. You can tell if you child is sick, not getting enough fiber, dehydrated, etc. This is true of animals as well.
All of the books spend many chapters on disease. The best way to tell if an animal is sick is if they 1) start acting differently then they normally do; or 2) poop is the wrong consistency or color. If a sheep's poop become all diarrhea-ish, then you have a sick sheep.
This happened to Norman Jr. Last winter, Norman got very sick. What was so bad about it was that we didn't notice his poop soon enough; or else we would have reacted sooner and he wouldn't have nearly died. One morning he was sleeping in the hay trough and wouldn't get up. Finally I got in and picked him up. He was laying in his own poo and he had lots of poo dried to his haunches, obviously he had been sick for a while. Bad, bad farmers we were!
We quarantined Norman, but kept him in the outside pen. We gave him a dose of dewormer. For a couple days he looked better. Then (I think it was the day after Christmas) Jeremy went down to feed the sheep and chickens. When he came back up he said "Mama, you might need to go down and say your good byes to Norman.''
Now for anyone who knows me (or who has read Pets vs Food), Norman is a pet and he is my pet. I bottle fed him. He gives me nose kisses. So having to say good bye to Norman made me queasy and choked up.
I went down the pen. He was laying on his side and couldn't get up. He was so thin. I picked him up and set him on his feet. When he tried to walk, he fell over. My first thought was that he may be dehydrated, so I got a plastic syringe (like you give medicine to babies with) and force fed him water. He didn't like this but he drank. We decided to move him into the barn and put a heat lamp on him.
Over the next couple of days we had to go down and lift him to his food and water. When he was strong enough, we let him out behind the barn to eat, but he kept falling over and we had to stay with him to right him again and again. This went on for a few weeks. Finally in late January, he was walking around and getting food without falling over. We put him back in the outside pen. A couple weeks later we put him back with the other sheep.
Today Norman is doing great. He is alert, eating great, defending his place at the oat trough against Notag, which is serious feat since she out weighs him by at least 50 lbs. And the most convincing sign he is fully recovered - his poops are back to nice little pellets!