Was Seth Hancock Right About Overbreeding??

[llbean]

Hi All,

In the Tome "Stud", the author quotes Seth Hancock as explaining that one of his reasons for not overbreeding his stallions is that if you breed to a stallion too many times each ejaculate will have less sperm and this will reduce the chances of getting a "Super-Star" sperm to impregnate the egg.

The more I think about this the more sense it seems to make because unlike Tesio's Nevous Energy Theory it actually gives a real explanation as to how overbreeding could undermine the quality of each foal sired by the overbred sire.

But the question is whether or not there's a connection between the motility/vitality of the individual sperm and the genes it encases and for some reason scientists seem to have not studied this question in any real depth.

Do any of the geneticists on this board and/or Pete have any ideas?

Thanks,

-llbean

[adrienne]

Motitlity and vitility are effected in overbred stallions because spermazoa is not allowed to fully mature before being ejaculated.

This is how sperm are made:


They have genes from primary spermazoa. DNA is DNA, imo. Sometimes you just get the short end of the stick.

The world of horse breeding is still stuck in mystery and tradition... This drives me up the wall. <g> It only takes a certain amount of sperm to reach optimum chance of insemination. You only have to breed every other day. There is no energy theory - just Sammy Sperm and Edna Egg having a chance meeting in the comfort of Ms. Oviduct.

~Adrienne

[KamiBrooks]

I'm a computer geek (not an expert or even very well informed on biology or TB breeding)...

Isn't it more likely that high volume breeding appears to reduce the chances of a "super star" because of the volume of poorly considered matings.

This is a separate issue from enough fertility to produce any foal.

[skeenan]

It makes sense to me... knowing some human couples who have had a difficult time conceiving, the doctor's advice to them was to try, then wait a few days before trying again, to let the "reserves" properly build up again... so I'm sure there must be a good reason behind it...

[Pan Zareta]

They have genes from primary spermazoa. DNA is DNA, imo. Sometimes you just get the short end of the stick.

The world of horse breeding is still stuck in mystery and tradition... This drives me up the wall. <g> It only takes a certain amount of sperm to reach optimum chance of insemination. You only have to breed every other day. There is no energy theory - just Sammy Sperm and Edna Egg having a chance meeting in the comfort of Ms. Oviduct.

Shades of that animated Disney short in 6th grade Health class!

Decreased motility (immaturity) and quantity (another artifact of 'overbreeding') both lessen the chance of impregnation. (Something that would be interesting to know is exactly how many mares going to the high-number sires are catching on one cover.) You're right that "DNA is DNA", but extranuclear factors materially affect how(or if) the embryo for which it codes develops and grows. Most of these are attributed to 'Edna', but are we sure an immature 'Sammy' can't negatively affect embryonic development? Would love to know Mary Syers' take on this.

[mary syers]

I believe Tessio. There's something about nervous energy and breeding a horse to 200 mares is bound to reduce the energy. Mary Syers

PS Good for Seth Hancocok to take a stand on this--it can't be popular with his potential and current clientele.

[Kari]

Adrienne- where did you find that chart? I'm in the reproduction module of my physiology class, and this is stuff I actually want to absorb!

[bcassidy]

It's been a long time since I graduated college with a degree in biology and chemistry, so granted my data could be a little outdated, however I do read as many articles and books as I can on breeding and genetics and I have never heard about a "super sperm cell" in any species, including horses, it is just not the way sperm cells are created. When you hear people talk about taking time between breedings it is usually for sires that have a problem with the number of sperm cells created, therefore a longer time between breedings will usually increase the number of sperm cells created for the ejaculate and I don't know that any sperm cells would go on to become "super sperm cells" if they were given more time in the testicles. As far as I know, all sperm cells are created the same way and there is no such thing as "super sperm cells".
Additionally, the notion of nervous energy is something that I have thought a lot about and my belief is that this was something that Tesio labeled because he didn't have the educational background to understand it better. It is very difficult for me to put myself in that time period and understand what someone of his day might or might not have known. Clearly science and technology have come a long way since then and some of his thinking could be explained differently today---such as the whole mitochondrial-dna topic surrounding the female egg. It probably won't be long before somebody proves me wrong but I would still prefer to wait for science to come up with some plausible arguments before I subsribe to such notions as nervous energy. Can anyone cite or refer me to some data to counter my opinion?

[adrienne]

When you hear people talk about taking time between breedings it is usually for sires that have a problem with the number of sperm cells created, therefore a longer time between breedings will usually increase the number of sperm cells created for the ejaculate and I don't know that any sperm cells would go on to become "super sperm cells" if they were given more time in the testicles.

Here is another important point to consider.

Before the beginning of breeding season at Iowa State University we would always collect the stallions daily or once every other day to recheck fertility and also to "flush out the junk". Usually, stallions after a time off are less fertile. Stallions that are active, without being over used, are at the peak of their fertility.

During my short stint in the 'real horse world' I worked under a farm manager who wanted to breed every day and each stallion no more than once a day. He would rather MISS MARES that break those two codes. ::slaps forehead::. I would also have to convince him to NOT tranquilize and breed mares that had gone out of heat days before... This is why I'm nutso about the entire thing.

~Adrienne

[mary syers]

Actually it takes more than one sperm to fertilize an ovum. This is what Dr. Ford taught me in Animal Repro. 301. 4 or 5 sperm penetrate the zona pellucida causing a change in this tough outer membrane of the ovum. One sperm goes through the zona and then the zona changes again to be impermiable to more sperm. Those caught in the zona self distruct and the single sperm forms a nuclear body inside the ovum, where it remains seperate from the ovum DNA for several hours. Actual fertilization occurs when the two seperate DNAs join.

The kicker to this is the paternal mitochondria. The energy to swim upstream and then penetrate the thick zona comes, in the sperm, from a cluster of mitochondria in the midpiece. Energy is produced by the mito's from fructose in the vaginal and uterine secretions(Fructose is a sugar that can be absorbed across cell membranes without the help of insulin--under the right circumstances.) Low energy, low functioning mitochondria--no penetration.

The second kicker: Something important happens in the hours post penetration when the two DNAs stay seperate from each other. I don't know what that is. I don't think anybody does yet. It's the time frame that tells you its important. Why wait hours to finish fertilization? What kind of energy needs are there for the sperm DNA in that time frame? We do know paternal mtDNA does penetrate the ovum and exists in the ovum for some time. So sperm mitochondria may be yet functional at this point in time.

The question is: what are the energy requirements to form an optimum fertilized egg? How much energy does the sperm need inside and outside the ovum? How good are sperm from a horse bred to 200 mares compared to a horse bred to 50 mares in producing the necessary energy? Nobody has asked any of these questions. But I suspect we will at least know the anciliary answer to this in the next 10 years. If fewer
"overused" stallions' foals go on and make money, then we will know there is a problem with energy.

Tessio was a good emperical scientist. He may not have known why, but he often knew what. Don't discredit nervous energy, just because the scientists are slow to expain. Just do what Tessio did--pay attention to the details. Mary Syers

[BJ]

How about a little old fashioned common sense...Too much of ANYTHING is not a good thing. Constantly breeding a stallion can't have a positive affect on his health, the sperm quality he produces, the resulting foals. Boy...wouldn't it be interesting to know WHEN any good foals were bred???? Were they all bred in the first few days of the breeding season???? How many mega horses were bred at the 188th breeding???

The only "good" coming from the overbreeding craze is the money overflowing from these stallion owner's and breeding farm's pockets!!!

[LSB]

Boy...wouldn't it be interesting to know WHEN any good foals were bred???? Were they all bred in the first few days of the breeding season???? How many mega horses were bred at the 188th breeding???

We do know approximately at what point in the breeding season each foal is bred--because we know their birthdates.

Someone posted a list earlier (maybe Louis?) showing that a number of this year's Derby entrants had late birthdays, including Bandini, who must have been produced at the end of a very busy breeding season for FuPeg.

I had two fillies born this year, one resulting from one of her sire's earliest breedings (Feb.22nd) and the other coming from one of her sire's last breedings (May 25th). In a couple of years, I'll let you know which one is better.

[BJ]

Boy...wouldn't it be interesting to know WHEN any good foals were bred???? Were they all bred in the first few days of the breeding season???? How many mega horses were bred at the 188th breeding???

We do know approximately at what point in the breeding season each foal is bred--because we know their birthdates.

Someone posted a list earlier (maybe Louis?) showing that a number of this year's Derby entrants had late birthdays, including Bandini, who must have been produced at the end of a very busy breeding season for FuPeg.

I had two fillies born this year, one resulting from one of her sire's earliest breedings (Feb.22nd) and the other coming from one of her sire's last breedings (May 25th). In a couple of years, I'll let you know which one is better.

FuPeg has only two crops on the ground of racing age. His stats of 295 foals "of racing age" and 199 "current 2 y/o's" *might* indicate FuPeg was bred to only 96 mares (or had only 96 foals) from his first crop at stud. (Bandini's crop).

http://ww2.equineline.com/bloodhorse/fu ... gasus.html

That being said, Bandini was a May foal, indicating that there was perhaps another month in that breeding season of 96 foals, or *perhaps* only 17.5 covers per breeding season month????? While perhaps not "ideal" numbers, they are certainly better than what they are now for FuPeg. Also, IMHO, the jury is still out on Bandini.

[LSB]

Don't forget that 2001 was an MRLS year, which caused many stallions to have smaller crops in 2002.

The reason I picked Bandini as an example is because--although I don't know the exact numbers--I would expect that FuPeg, standing his first year at stud at Coolmore, would have been busier than 95% of the stallions in Kentucky.

The "jury may still be out" on Bandini, but you asked for examples of "any good foals". Surely, as a Grade 1 stakes winner, he would have to qualify.

[adrienne]

<<The question is: what are the energy requirements to form an optimum fertilized egg? How much energy does the sperm need inside and outside the ovum? How good are sperm from a horse bred to 200 mares compared to a horse bred to 50 mares in producing the necessary energy?>>

But these sound like questions of the possiblity of decrease in embryo viablity rather than decrease in embryo quality.

Here are some statistics to think about:

On average, a normal stallion produces 35,000 spermatozoa per second and then up to 70,000 per second during the peak of breeding season. Thus, the average stallion produces three to six billion sperm per day. With AI in the QHs at ISU we insemination fresh, on farm with 250 million live sperm. Even breeding 3 times per day, a stallion should still have enough sperm hanging around that are produced anyway to get the job done.

Heck, the TB stallion at ISU was {fertility tested} through collection. One day over 4 collections his concentration, progressive motility, and overall sperm count INCREASED. No one is saying thats normal, LoL, but it's possible.

So I think the heart of not over using stallions should be in basic humane care. Stallions cannot be expected to stand up to the stress of overbreeding. It's that simple. No one who seriously cares for their stallion breeds him to 250+ mares a year. And no one who knows a lick about marketing breeds him to any given nag whose owner will pay the stud fee.

<<wouldn't it be interesting to know WHEN any good foals were bred???? Were they all bred in the first few days of the breeding season???? How many mega horses were bred at the 188th breeding???>>

Even if a statistical connection between late foals and lack of quality COULD be established, there are also many more 'real' factors there. Like these are more likely to be foals of older mares, mares prone to inflammation and infection, mares directly off the track, and of course the later birth date in respect to maturity... etc. etc.

~Adrienne

edit: 6/29 7am: no one test bred the tb with AI it was purely a microscope thing