Labrador Retriever Forum
Well, I searched around through the breeding articles I keep and also did a google to find the exact information I wanted to pass along. No luck! I have routinely collected males I managed who were not used often. This stimulates the production of new sperm cells in a normal, healthy male. HOWEVER, what I wanted to include was how long it takes for that new cell to mature and be ready for ejaculation. If you are planning a breeding soon (in the next week or so), I would not pre-collect the dog. Yes, there will be some old sperm in the semen, but there will also be plenty of good ones. Since it takes (off the top of my head's poor memory) about 60 days for new sperm cells to mature, you don't want to deplete the current supply needlessly.
If two breedings are planned, I would do the first one a bit early and the second on the prime day. This is for two reasons. First, most of the old sperm cells will be in the first collection, so they will be out of the way for the "prime" collection. Second - and a very important factor for ME - you will be more likely to get a good gender mix in the pups. Breeding at just the "right" time assures that the faster swimming male sperm are the first to arrive and many litters will be mostly male. By doing a breeding a few days earlier, the male sperm in the first collection will mostly be dead and the slower female sperm will be in position to fertilize the ova when the time is right. Adding a fresh batch at that time willl assure that plenty of males get to the party as well 
For what it's worth, I collected a 5 year old male that had NEVER been used for breeding and we wanted to see if he was fertile because someone was interested in him. His sperm was jumping off the slide. I liked himm so well, I bred him to one of my girls, before he left for Italy and had 8 pups.
Don't males "release" ummmmmmmm, well.......yah know
sperm on their own?
my boys hump each other and on occasion even have an outside tie while just playing?? Are we over sexed here or what?
I didn't understand any part of that last paragraph except my name - sort of like a dog hears
I did find one of the references I was looking for - here is an excerpt:
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It takes a long time, about two months, for a newly born germ cell to mature into a fully equipped sperm cell, at which time it is shed into the duct, ready to be cast out into the world. It's slow, but remember...there are hundreds of meters of this stuff constantly trickling out new sperm, and it adds up.
Once sperm complete their development and are cast off into the duct, they next migrate to the epididymis. The epididymis is another tightly coiled duct, about 6 meters worth packed into a 4cm long rope, that clings to the posterior edge of the testis. It is a sperm storage organ, and the place where the sperm acquire motility and have various other essential molecular functions finally activated.
The next step for sperm is the ductus deferens, or vas deferens, a long tube that extends from the back end of the testis, up into the body, in front of and over the pubic bone, around the urinary bladder, and finally to a region called the ampulla, were it merges with the seminal vesicle before entering the prostate gland. This roundabout route is a relic of it's embryonic development, when the testicle migrated from its internal position to its final place in the scrotum. The vas deferens also stores sperm, for up to several months, and the seminal vesicle and prostate are responsible for adding seminal fluid to the concentrated sperm stored in the duct.
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So, a male stores a bajillion mature sperm and releases them a batch at a time in an ejaculation. Two references I read (neither of them Dr. Hutch) said that daily collection does deplete the mature sperm after about 4-5 days so that an individual collection may not have the target number (100 million)of forwardly motile, mature sperm to achieve a litter. The recommendation was for every other day or every third day to leave some of those bajillion in the tank while the new ones are maturing. 
