A study on mare age

[Simengineer]

Several months ago this forum brought up the question of does the age of the mare really matter. I decided to gather some data, it is what I'm best at. Biology aside, I took what I call a random sampling of stakes winners. How random a specific requirement can be is debatable, and I did not make distinction of quality of stakes race, but there it is.

The mares age at the time of the stakes winners birth came out like this:

age number of stakes winners
5 8
6 14
7 11
8 16
9 13
10 8
11 11
12 2
13 5
14 2
15 1
16 3
17 2
18 1
19 0
20 0
21 3

It seems pretty clear that although you can get lucky and get a good runner late, you are far better off before she's 12.

And similarly here is the foal position of the stakes winner:

1 15
2 27
3 16
4 16
5 10
6 3
7 3
8 2
9 4
10 1
11 0
12 1
13 1
14 0
15 1

This chart clearly shows the a mares second foal is her best bet.

Any comments?

[majxmom]

I have heard before that there is a high percentage of second foals being the best.

[Danzig]

Is the quality of a foal a function of it's mare's age or the viability and health of the uterine environment?

[Strategic Maneuver]

IMO, a mare's age versus uterine viability are one and the same. Younger, stronger, etc. But then again, nothing is ever written in stone when it comes to thgb's. I had a 23 yr. old mare throw her only stakes winner and she's still yard art at 30 yrs. old. But the numbers don't lie. Younger is better and another factor to be considered is yrs. the mare/filly raced.

[KBEquine]

There have also been some studies that suggest a mare is bred to the best stallions of her broodmare life her 1st 3 to 5 offspring. So in addition to factoring in age & uterine viability, her later offspring may be by unproven [and possibly unprovable] sires trying to use her to make a name for themselves & the fault, if any, may not lie solely with the mare.

[foothillsequine]

We cannot forget Somethingroyal, who at 18 foaled the triple crown winner--Secretariat!

[Hold Your Peace]

There have also been some studies that suggest a mare is bred to the best stallions of her broodmare life her 1st 3 to 5 offspring. So in addition to factoring in age & uterine viability, her later offspring may be by unproven [and possibly unprovable] sires trying to use her to make a name for themselves & the fault, if any, may not lie solely with the mare.

Excellent points.

In these numbers you see a dramatic drop off in stakes winners after the fifth foal but a lot of that makes perfect sense.

For one thing, a lot of mares will never produce a 6th, 7th, or 8th, or so on . . . foal because they might die or become reproductively unsound before they ever get a chance to produce that many foals. Or if the mare is tough to get in foal and keep in foal from day one, it might take her twelve years to produce her sixth foal. (It's kind of like post position stats, you might see or hear a stat that no horse has yet won from the 12 post at the meet but further research may reveal that there are rarely more than 8 or 9 starters in a race at that track and it may be that there's only been one or two horses in post 12 at the entire meet).

And also, a lot of high class breeding programs are going to cull a mare before she produces her 6th, 7th, or 8th . . . foals if none of the early ones impressed them. Now someone may buy the mare and keep breeding her but as you pointed out the new owners are liable to be breeding her to stallions of much lower quality which makes it much less likely for her to get a stakes winner.

That doesn't mean that there's nothing to the idea of younger mares being better, but the above points are just something that should be considered when evaluating these numbers.

[Gillies-Fillies]

Well said, Hold Your Peace. And neat topic, Simengineer.

The sample of 100 shows 16% of stakes winners as being the 6th or later foal from their dam... I wonder how that compares to the percentage of foals born in that category?

It's easy to name hundreds and hundreds of mares that had a dozen or more foals, but for each one of them, there's a barnful of mares that stopped at five or fewer foals. Making the question one of opportunity.

[newyorkmary]

I agree with Holdyourpeace and kbequine. You should try to control for otherfactors - stallion quality, the fact that there are fewer foals born to older mares and fewer foals born as a mare's 6th, 7th, etc. foal, and many others -in order for your analysis to be compelling. I would be interested to know if such a study has ever been done.

[Simengineer]

There is some really great ideas for more research here. I've lost my original list of stakes winners I started from so I will have work up another one. No problem there as it did not really take that long. The study was done specifically from the stakes winners, not the mares themselves so there were plenty of young mares and old mares in the mix. A study of stallion quality a mare receives will mean a group of older mares. That should be really interesting.

[KBEquine]

Remember also the tax laws only allow depreciation for so many years - the older the mare, the more likely she'll hit an auction with no reserve because her soon-to-be-former owner can't depreciate her any more & made a business decision to sell her. Typically, part of that business decision is that mares sell better in foal, but don't sell very well, anyway. SO the soon-to-be-former-owner hedges his bets/costs & gets the cheapest season he can find & unless he luckily hit a diamond in the rough, the mare gets bred to a lesser stallion & the "older mare" statistics suffer . . .

[Mac]

Based on my own experiences, I agree with KBequine and several of other posters' thoughts that old mares can still produce quality progeny if an old mare could (1) could get pregnant as often, and (2) have the same opportunities to be bred to quality stallions and consequently,(3) have her later foals still have access to excellent training programs.

Because I have several old mares, I also did a study of about 200-300 stakes winners out of OLD mares. What I was wanting to find was examples of stakes winners where the mare was bred to the SAME stallion many times over her breeding career. There were very few examples of this, as most mares are bred to numerous sires, especially in recent years. Obviously one example was Somethingroyal in which Secretariat came from her LAST mating to Bold Ruler, not her earlier matings. Another example was a mare whose name I forget, who was bred to In Reality about nine times. Her three graded stakes horses by In Reality included the second, the fifth, and the next to last. Something like that. There were a few more examples. Anyway, the end result of my study of such mares did not indicate that the quality of their foals declines that much late in life IF ALL OTHER THINGS ARE EQUAL, as in, the same class of stallion and presumably the stame quality of training conditions. I DO think that mares' ages can impact the quality of the foals negatively in some cases, but I don't think it is as significant an impact as a first glance might reveal, for many of the reasons KBequine and some others of you have cited.

Once I finished my study, I was actually encouraged that buying older mares was one way to get access to some exceptional genetics on a beer budget...

[zinn21]

Mac, you might be on to something. If one could legitimately identify certain criteria in older mares that lead to producing quality foals, you could add a lot of value to your breeding program.

I would think the quality of an older broodmare's foal carrying environment would be bottom line critical in producing a quality foal, thus a case for case pre natal exam by an experienced reproductive vet is essential.

[Dave C]

I think Mac's approach is the correct approach to studying this effect (if it exists). If the selection criteria for the study is that a horse is a SW, then another criteria should be added that the mare had to be bred to the same stallion at least 1 other time, and that other foal should be added to the control group (assuming that it wasn't a SW). In this way you control for the stallion quality changes that a mare may experience over her career.

The way I would prefer to establish selection criteria is that you select mares for the study based on the mare being bred to a stallion multiple times (preferably 3 or more) and produced at least one SW from those matings. You may also want to control for gender since a younger full sister to a GSW may be retired early or unraced because of her value in the breeding shed.

[freshman]

Statistically, young mares are more likely to throw a good foal than an older one, if only because younger mares are more likely to be alive. The same mares that have a stakes foal at 5 might be dead at 10--comparing her stats to an aged mare isn't valid.