Hi FM
Do dosage indexes are calculated by establishing where and how many
chefs-de-race appear on a horse's pedigree. Chefs-de-race are sires who not only have a great influence on their breed, but their influence can also be categorised by the type of progeny they produce be they precocious speedy sorts or those given to stamina. Each chef-de-race is assigned one or two categories (aptitudinal groups) according to the nature of their influence. These are;-
Brilliant - Nunthorpe/Prix de l'Abbaye
Intermediate
Classic
Solid
Professional - Ascot Gold Cup/Prix du Cadran
Should such sires appear on a horse's pedigree, points are allocated based on the proximity. Sires get 16, grandsires 8, great grandsires 4 and fourth sires 2. Points are split if the sire has multiple categories. The points are tallied and the sum total of brilliant and intermediate, plus half of classic, is divided by half of classic plus solid and professional. The result will be the dosage index. The higher the dosage index, the greater the propensity for speed. The lower the dosage index, the greater the propensity for stamina. In theory of course...
We can use My Drogo as a demonstration on how we reach the Dosage Index.
Here is his pedigree with the
chefs-de-race highlighted.
And here is the
chefs-de-race list with the above influences also highlighted.
So let's start with the first generation. Milan is not a chef-de-race - which ties into one of the many limitations of the Dosage Index system. While Milan is patently a strong stamina influence, he is not prolific enough on the flat, nor impactful enough on the breed in general, to warrant a place on the list. Incidentally, another notable absentee is Danehill whose impact on the breed has been emphatic. Nevertheless, since his aptitudinal scope is so broad (his offspring encompasses such a diverse range as to include Mozart, Rock Of Gibraltar, Duke Of Marmalade, North Light and Westerner), he could not be placed in any one or two category.
OK, so sire Milan = 0
Grandsires. Sadlers Wells is in C and S so the 8 points are split between the two. Running total;-
B-I-
C-
S-P
0-0-4-4-0
Great grandsires. Northern Dancer [BC] and Darshaan
. 4 points each. Northern Dancer's split between B&C, Darshaan's S gets all 4.
B-I-C-S-P
2-0-6-8-0
Fourth sires. Shirley Heights [CP] and Northern Dancer [BC]. 2 points each. Both split.
B-I-C-S-P
3-0-8-8-1
First half
3+0+4 = 7
Second half
4+8+1= 13
7/13 = 0.53846...
My Drogo's DI - 0.54
As this is a low DI, due largely to the influences of Sadler's Wells and Darshaan, My Drogo is more likely to be a staying type than a sprinter.
Broadly speaking, DI is more applicable to the flat than jumps, largely due to the notion that speed generally gives way for stamina as a horse matures - as discussed in the above posts.
As for the 0.5, 4/1 etc. This is something I have come up with myself as a means of quickly showing how closely related one horse is to another on the damline. The first figure denotes "the x dam is" and the second figure denotes "the x dam of". So instead of saying such a horse's granddam is out of a sister to the great granddam of another such horse, I just write 4/4 (I think... I've confused myself trying to work out how these imaginary horses are related which is why I find the number system so useful).
So 0.5 is indeed half-sibling. 1/1 is full-sibling. 1/0 will be the dam - the first dam is - so
My Drogo 1/0 My Petra = My Petra is My Drogo's dam.
From there, 2/1 would be the second dam is the first dam of.
Monmiral 2/1 La Landiere = Monmiral's granddam is the dam of La Landiere / Monmiral's dam is a sibling of La Landiere / La Landiere is Monmiral's Auntie.
Being a little more adventurous, using this table, we can see that Faugheen is related to Rocky Creek. But instead of going through the rigmarole of describing their relationship, it is simpler to just pinpoint the common ancestor on the damline which would be Marteline. Since he is Faugheen's fifth dam, and Rocky Creek's fourth dam, Faugheen 5/4 Rocky Creek.
