A normal gestation period for a doe goat is 145-155 days with the average gestation being 150 days. Some goats, such as the Swiss dairy breeds are seasonal breeders and only come into heat (estrus) in the fall while the meat and dual purpose breeds may breed year round. A doe will go into heat approximately every 20 days and that is when she will be receptive to a buck. She will start to act strange-mounting other does and allowing other does to mount her, flag or wag her tail frequently and become exteremly more vocal than normal. If a buck is in a nearby pen she will spend a lot of her day near the fenceline calling to him. She will remain in heat for 2-3 days and if not bred will repeat the cycle until she becomes pregnant.
The buck will usually be near his side of the fence doing many strange antics if he senses a doe in heat neaby. A buck that is in rut will make funny grunting and snorting noises, pee on his face and raise his face high into the air with his upper lip raised. They will also begin to emit a very strong, offensive odor called musk that the doe goat will find attractive. If you milk your does too close to a smelly buck in rut the smell can be transfered to the milk causing the milk to be flavored by his musk.
If at all possible, you should attempt to be present when a doe is bred. Then you will be able to record the extact date that the doe is bred and watch for her next heat cycle to see if the breeding takes and she is pregnant. At that point you will be able to calculate the due date and be better prepared to see her kid and be present in case she needs assistance. If she is a doe that is in milk, she will need to be dried off - forced to stop lactating - about 2 months prior to her due date. Some does will begin to trend down their milk volume automatically, but occasionally a doe will not stop making milk. This is bad for the newborn kid since the mother may not produce colostrum for her kids to eat if still in milk at the time of delivery. To force a doe to stop lactating begin only milking the doe once a day for a week. Then let her go every other day without milking for a few days. After that, stop milking entirely. Watch the doe carefully for signs of mastitis -fever and abnormally hot milk bag in one side or both. After a few weeks the milk in her bag will absorb back into her body. She may be uncomfortable during this process, but the pressure in her bag is what tells the lactation cells to stop producing milk.
Once the doe is about 2 weeks from her due date she should be confined in a kidding pen if the weather is very cold or otherwise severe to insure survival of the kids. If the weather is mild she can remain with the herd and be allowed to kid outside. Occasionally another doe will help the mother clean her kids if she has multiples so that the mother can work on delivering the next kid.
When you notice the mom and her new arrivals, make sure to iodine the navels to help prevent navel ill and get them latched on to mom for a tummy full of colostrum. Don't foget to give mom a treat as a reward for all her hard work as well - a gallon bucket full of warm water with 1/4 cup molasses and 2 tablespoons each of salt and baking soda will be greatly appreciated!