Was Seth Hancock Right About Overbreeding??

[adrienne]

<<Therefore, the Best Sperm in an A.I. sample will likely be inferior to the best Sperm in a Full Ejaculate in the same way that the highest I.Q. high schoolers in random sample of 1,000 will likely get significantly better scores than the highest I.Q. high schoolers in a random sample of only 100.>>

No offense, but you need to take a statistics course.

Learn about the bell curve distribution here:
http://facultyweb.cortland.edu/andersmd ... mcurv.html

Here is my bell curve:

[mary syers]

Adrienne,
An aside in this argument: how do we nominate Dr. Miller for this new Iowa Horse Board? She's the right person in the right place. Mary Syers

[llbean]

Adrienne,

I can't see the relevance of the Bell Curve concept to my main point.

I'm not saying there will be higher percentage of Super-Sperm in a full ejaculate than in a sample taken for the purposes of A.I. What I AM saying is that so long as the same of percentage of Super Sperm is found in the sample as in the overall ejaculate there will be more Super Sperm in the full ejaculate than in the A.I. Sample.

More Super Sperm = A Greater Chance Of a Super Sperm Getting To The Egg First, I think. Like you have pointed out, a small number of super sperm could have there natural betterness undermined by uterine contractions and many other dangerous factors. Therefore is it not logical to have AS MANY Super Sperm as you can to maximize the chances of at least one of them getting there first??

And my point about the High Schoolers is still correct as I never said the larger sample would have a greater concentration towards the higher I.Q. end of the Bell Curve. I merely intimated the common sense truth that the 20 Highest IQ Students taken from a sample of 1,000 will have higher scores than the 20 Highest IQ Students taked from a sample of 100.

I implore anyone on this board who understands statistics to contradict me if they can do so honestly.

BTW, I say a "Common Sense" truth as if you asked someone which of three Countries, America, Aruba, or Monaco, is likely to have the best top Chess Players, most people would rightfully say America even if they never ehard of Chess before on account of the simple fact that there are many more people in America than Aruba or Monaco.

-llbean

[Heidilady]

And my point about the High Schoolers is still correct as I never said the larger sample would have a greater concentration towards the higher I.Q. end of the Bell Curve. I merely intimated the common sense truth that the 20 Highest IQ Students taken from a sample of 1,000 will have higher scores than the 20 Highest IQ Students taked from a sample of 100.

I implore anyone on this board who understands statistics to contradict me if they can do so honestly.

I started to give a crash course in Advanced Placement Statistics but it's late and I don't plan on giving myself a headache on account of this thread. Also, it takes too long since I'm kinda verbose as a general rule and I decided to delete the long mess I started with (I wasn't entirely successful as the rest of my post will demonstrate..wow I talk too much). Sufficed to say Adrienne is right due to at the very least the following possibility as an option. We're talking about likelihood here and a larger sample size makes it more likely that your sample represents the whole sperm count (impossible to measure as far as we're concerned right now). Remember a sample size is just a representation of the whole and it outta look like a bell curve in the end if you had the entire sperm amont to work with with most of the sperm being in the middle and equally likely to be duds as super super potent.

Edited to add: of course "dud" and "super super potent" are relative per stallion. The median for one stallion could be different than another and a "dud" sperm as far as one stallion is concerned could be the median for some other stallion. Example, the average Storm Cat foal could come from a certain "level" of sperm that would be at the far high end of another stallion's sperm "level" and he'd really have to have some awesome sperm to be in Storm Cat's middle range.

To go back to the high school IQs, the 20 top "scores" could in fact be equal or with a smaller sample size of, say 100, you could end up with the dumbest 100 people or the 100 smartest, you don't know. It's possible that your 100 high school students at random in a student body just happened to get alot of people near the top but that your 1000 got many near the bottom and middle and the top 20 don't quite match that same as from the sample of 100. I'm going to shush now, let that digest, and hope that you can understand it and I didn't give everybody reading this a migraine. If I did, I blame it on the movie Big Fish which I'm in the process of watching.

[xfactor fan]

Ahem,

Folks please go and at least look at the link to sperm production.

It sure looks like there is no connection between the DNA in the chromosomes and the process that forms the body of the sperm.

So no matter how it gets to the egg, it is a matter of luck what chromosomes are passed on to the resulting foal.

http://distance.stcc.edu/AandP/AP/AP2pa ... ermato.htm

This may however explain the decline in quality foals once the stallion gets up there in age.


Looks like the pre-sperm cells which contains a double set of chromosomes--2 Y's 2X's, 4 chromosomes 1, 4 chromosome 2..., splits one becomes a duplicate of the original cell the other in turn splits into 4 proto sperms cells, that then eventually turn into the regular sperm with tails, heads and other body parts that all good sperms need.

Back to the pre-sperm cell. It is now a copy of the original. The process goes on, to make another 2 copies, one to replace the original cell, the other to generate 4 sperms.

So by the time a stallion is 17, or 18, the original germ cells have been copied a whole lot of times. This allows any errors that may occure to be copied and passed on to the next generation of sperm cells.

For example if two of chromosome #6 don't duplicate correctly, leaving two normal chromosomes, and two damaged chromosomes, the sperm genesis will produce two normal sperms and two sperms with abnormal chromsome #6's.

Repeat this a billion or so times, and the rate of accumulated chromosome damage may explain the statistics on older stallions.

On the other hand, there may be a whole lot of crossing over (this if the chromosome version of sex- where chromosomes swap parts) going on in the proto sperm cells.

Two copies of the Y and X, 4 of all the other chromosomes. This may be natures way of keeping the gene pool from stagnation.

A question for those involved in AI. Does the rate of sperm production go up with frequency? Not the rate of mature/immature sperms, but the over all rate of production.

[llbean]

It sure looks like there is no connection between the DNA in the chromosomes and the process that forms the body of the sperm.

Where is the evidence that it looks like that?

-llbean

[madelyn]

xfactor, to over-simplify for my pea brain, the constant replication of sperm from the last copy can cause degradation? Something like continuing to photocopy from the last photocopy, eventually will result in a lot of distortion from the original? So it wouldn't necessarily have to wait until the stallion was 17 or 18, it could happen at 6 or 7 if he had a massive book of mares every year?

[Pan Zareta]

It sure looks like there is no connection between the DNA in the chromosomes and the process that forms the body of the sperm.

Are you saying that mtDNA directs the formation of the body of the sperm??? I thought genes on the Y chromosome (yDNA) controlled most, maybe everything, to do w/ sperm production...

[mary syers]

How about this. The whole mitochondrion in the sperm is taken from the germ cells producing the sperm. Each sperm has 30-40 mitochondria. What if in high production the mitochondria in the sperm producing cells can't split and reproduce fast enough to keep up with demand? What if mtDNA copy number per sperm mitochondrion is lower due to rapid turn over and reproduction of sperm. Fewer copies of mitochondria with less mtDNA--less energy per sperm leads to lower fertility. Anybody? Mary Syers

[xfactor fan]

Just to recap: Is there a connection between the size, or health of a sperm, and the set of chromosomes contained inside the sperm head.

Secondary to this question is what controls the body formation of the sperm.



It looks like the basic command -Go forth and be sperm- happens to the parent cell that contains the duplicate set of chromosomes. This cell splits, one becomes the new parent cell, and the other splits into two cells with a normal number of chromosomes, and then these two split again into four cells with half the normal number of chromosomes.

This make biological sense, the sperm production is started with the cell with not only the usual number of chromosomes, but one with a complete backup.

No sperm, no next generation, so this would be a real good place to install a fail safe.

Yes, it is likely that the Y controls lots having to do with sperm production, but it sure looks like the whole process in set in motion before the cell splits down to the haploid set.

In other words I think the process is controled by the genes on the chromosomes, but that the process is not related to the tighlty coiled chromosomes inside individual sperm cells.


A copy machine is a good analog for cell replication of the parent cell with the double set of chromosomes. Any changes would be faithfully reproduced in all of the cells that follow from that original change.

Another question is does the rate of sperm cell production go up with the increase in covers?

So if a stallion covers 30 mares a season, then covers 300 mares the next season, does the actual sperm cell production accelerate, or does each sample contain fewer sperm?

If there is acceleration of cell activity, then there should be an accelerated rate of changes in the parent cells, which could result in a 10 year old stallion having "aged" cells like that of a 20 year old stallion.

If this is the case then the "Hancock theory" may have some bearing. Not because there are more "super sperm" but because the chromosomes in the sperm have acquired less changes.

Mary, I like the idea the the mtDNA can't keep the pace with cell division, but it is probably more likely that the cells don't split evenly when going down from 1 to 2 to 4. Either the cells don't share the cytoplasm evenly, or that for some reason most of the mitochondria and not evenly distributed in the cytoplasm.

[mary syers]

xfactor fan,
The truth is we are probably both right. More sperm production, less eveness in cytoplasm division and less mitochondria to split between sperm, less energy per sperm, poorer total sperm. But probably still soon very good ones in the mix. Mary Syers

[llbean]

In other words I think the process is controlled by the genes on the chromosomes, but that the process is not related to the tightly coiled chromosomes inside individual sperm cells.

Then why aren't all Sperm from the same stallion essentially identical?? It's not as though Sperm are nearly as complex or self actuating as Identical Human Twins, where what differences there are between one and another can be explained away by enviromental factors and/or free will.

It looks like the basic command -Go forth and be sperm- happens to the parent cell that contains the duplicate set of chromosomes. This cell splits, one becomes the new parent cell, and the other splits into two cells with a normal number of chromosomes, and then these two split again into four cells with half the normal number of chromosomes.

Yes, but most of the Sperm's Growth into a Sperm takes place after half the Genes are Gone and completely unavailable to the Sperm, right???

"Making A Horse"

Half A Genotype + Half A Genotype = A Horse Zygote

"Making A Sperm"

All A Genotype - Half A Genotype = A Horse Sperm

These are two sides of the same coin, the only difference being in which direction you play the film, are they not?

Saying that the development of the Sperm is completely controlled by the entire Genotype of the Stallion just because at one early point in it's life it had all the Genotype makes no more sense to me than saying a Zygote's development is completely controlled by the half Genotype of the Sperm that created it with the Egg on account of the Zygote being a Sperm at a early stage in it's life.

Also, I have a very hard time believing that the Genes of a Living Being can be superfluous when you consider that Scientists have thus far failed to find a single thing that can properly be termed Life lacking DNA and/or RNA of some kind (unless you want to pretend Prions or Crystals are alive).

And moreover, what a Living Thing does on a Cellular Level it does because the Genes tell it to. Thus if a living thing is not being told what to do by it's Genes; it will not do any of the things we use to tell apart the living and the dead and is thus either Dead or in an Extreme Dormant State.

I bring this up as Sperm are manifestly alive.

-llbean