Reproduction
This is a big and controversial topic. I will keep it short and offer my opinion; but you can do what feels best for you, your dog and your family. This is how we should always looks at information.
There are times when we add a dog to our family that we cannot make a decision to or not to sterilize our dogs. Often we get a rescue that has already had the procedure done. They may even have had a very early removal of their reproductive organs (approx. 8 weeks of age) that many rescues, shelters and some breeders are now doing.
But, and this is a big but; should we be removing essential reproductive organs on our dogs early? The average age to spay or neuter has been around the six month mark. But there is significant research that has been and is being done about the subject; which is leading to the idea of later removal of reproductive organs or better still using alternative methods to sterilize.
Dr. Karen Becker is an advocate of saving the ovaries (removing the uterus) and gonads (vasectomy) so that the dogs maintain their important hormones I know that my next dogs will have these procedures over the complete removal of ovaries, uterus and gonads.
There is research showing that early removal of reproductive organs can play a part in behavioral and health issues. There is much to think about.
Males
Like humans, dogs have testes or gonads. Sperm and sex hormones (testosterone and follicle stimulating hormone) are produced in the gonads of the dog and require them to hang outside of the body. A common issue is having one or both testes tucked up inside the body where they cannot produce sperm properly. These dogs are often pulled from breeding stock and neutered immediately.
Males often have an extremely difficult time being around females who are in estrus. This is a main reason why many breeders do not keep males and hire out for stud instead. They will often stop eating, howl and generally go nuts (pardon the pun) when in the presence of a female in heat.
Like the females there is research now that later neutering or vasectomy is a better option for our dogs.
Females
Like us female dogs have similar reproductive parts. They have a vulva, cervix, uterus, fallopian tubes and ovaries. Unlike us their uterus has two horns; where puppies attach along the horns if they become pregnant.
Typically females come into estrus or heat around the age of 6 months but it can be earlier or much later. After their first heat they will on average, have another around 6 months later; but again that can be different as well. They are very individual and the average is an approximate time that genetics can play into. Often a female will come into estrus when their Mother did.
When a female canine comes into heat her vulva will swell and she will start to bleed. Normally a heat lasts between 14 and 21 days. Bleeding and swelling usually starts about a week in and the female will be attracting suitors. Many females will be extremely promiscuous when they are able to concieve and will persue males. At this stage the bloody discharge will become less red and become less until it is over.
When you have an unspayed female you must take great care that she is not bred (that is unless you want her bred). Males will do crazy things to get to an intact female so be aware how serious it is and that it will be like keeping her in jail for a few weeks. I cannot tell you how many people have told me that they are having or had an oooops litter. Keep this in mind if you are waiting for one or two heats before spaying.
Research shows that it is best to wait to spay your female until she has had at least one estrus. And perhaps look at the possibility of just removing the uterus and not the ovaries. More and more vets will be following suit in the near future.