1. Pneumonia. Goats have small lung capacity. If a goat happens to be down from some other illness or injury they much more easily contract pnemonia because they are most likely laying around more (possibly in damp conditions) it is more possible for fluid to build up in their lungs and their immune system is also being stressed and thus it not as able to quickly combat an infection. Any time you have a goat that is unwell do preventative measures to keep pneumonia away such as supplementing with Vitamins B,C,D,&E, herbs that help the immune system (echinacea, golden seal, garlic, comfrey etc – most goats love herb teas), use VetRx drops or eucalyptus oil. If a goat is unable to get up, turn her from side to side frequently and if she is able to rise get her up and walking a few times a day. This reduces fluid build up in the lungs. Watch for any signs of pneumonia – rapid, loud, or labored breathing and/or increased nasal discharge. If possible you may want to get your vet to diagnose it if you are unsure however DO NOT WAIT to treat. If your goat appears to be coming down with pneumonia on Sunday morning do not wait to treat her until you have seen your vet on Monday. Time is of the essence to keep lung damage down and to give the goat a much better chance of coming through alive. [soon I plan to have a link here for you with more on symptoms and treatments.]
2. Bacterial infection in the intestines.(Also sometimes called enterotoxemia) Any time a goat is off feed for a while, eats to much of a certain feed, has her diet changed, or is ill and being given antibiotics there is a good  chance that the normal bacteria present (and so needed) in her digestive system are diminished or upset and the environment quickly becomes a place where the other bacteria that was kept at bay by the good bacteria is able to proliferate very quickly. Depending on the age of the goat and how severe the goat can die before any outward signs (mainly diarrhea) are present. Again prevention is the key! Have some type of probiotic always on hand. This could be a commercially available product made just for the purpose – such as probios – or it could be a live culture store bought yogurt (Dannon and some others – check) or your own homemade yogurt. At the first signs of stress give probiotics!
3. If I would pick a third it would for sure be worms. Many goats die each year of parasite overload and many of the goats that die of the above two mentioned conditions are already unthrifty because of parasites. Parasites contribute to those above mentioned conditions being able to get a hold. Keeping your herd worm free is very important. Goats main resistance to worms is their eating habits. When goats eat near the ground they quickly pick up worms.

Hope to have more added here soon on symptoms on treatments