Well, every species decided which male to use.....each species has its its own method of choosing a mate.....perhaps a certain dance as in some birds, lionesses like males with darker mane (dark mane show higher testosterone), and a hen is no diffferent......she chooses the male that she likes the best because for some reason she feels that his offspring has a high chance of survival, perhaps his spurs are longer, maybe he finds better food etc. It's been shown in the animal world, that the males chosen usually have a higher testosterone level, making them stronger, more fit and better at survival. The wild horse with the biggest harem, the snake that wins the fight etc etc.
But when they breed, the male releases thousands of sperm into her reproductive system. One example that was present to me was the "lock and key". The egg is surrounded by a membrane that is coated with a certain chemical. When the male releases thousands of sperm, many of those sperm die before they can reach the egg, thus starting the whole "survival of the fittest". Only a couple thousand of the strongest sperm reach the egg. EACH sperm tried diligently to open that egg, literally by "knocking" on it with their head.
At this point, of the few thousand that I have made it this far, saveral hundred will be strong enough to knock of a "cap" that sits on the very end. Once that cap is off, the egg can read the chemical make up of each individual sperm. The sperm that the egg chooses must have a certain chemical secrection, it's this chemical that caused her to open up, allow THAT sperm in, and then reclose. The other sperm cannot enter, because their secretion does not stimulate the egg.
If it were a matter of the sperm eating and digesting its way in, then there would be nothing to prevent multiple sperm from entering the egg to begin with, and nothing to stop more sperm from entering after the egg has been fertilized. The sperm cannot eat its way it...it would leave a hole that would allow other sperm to enter. The egg must open up and allow that sperm in, then reseal itself to prevent further sperm from entering.
Once the egg has been penetrated, the membrane is deploarized, thus preventing more sperm from entering, and this chemical process is what caused the nuclei of the egg to divide the first time.
And technically the egg doesn't choose the sperm it's the first one to eat through the vitelline membrane that surrounds the egg, generally the strongest of the batch. The chances of only one making it would be greater if there were less to begin with, so that would be my concern with using a younger buck. That he wouldn't have enough yet to get the job done.
I about fell out of my chair!!
