Coefficient of Inbreeding

AN INVESTIGATION INTO WRIGHT’S EQUATION AND HARDIMAN’S METHOD

Wright’s Equation and Hardiman’s Method are both based on the principle that the inbreeding of an individual is one half the relationship of its sire and dam, however the calculations involve different data and so the inbreeding coefficients produced by them are not interchangeable and should not be compared with each other. Wright’s Equation is haphazardly calculated to any number of generations, whereas Hardiman’s Method is always calculated to five generations. Wright’s Equation considers duplicated ancestors only if they are common to both sire and dam, whereas Hardiman’s Method considers all duplicated ancestors. Wrights Equation considers inbred ancestors only if they are duplicated ancestors, whereas Hardiman’s Method considers all inbred ancestors. It should be noted here that an inbreeding coefficient is of little value without a standard with which it can be compared, so the proposed Register of Inbreeding Coefficients will be used to calculate a breed average for comparison.

STANDARD INBREEDING COEFFICIENT – includes only the subject’s inbreeding in the first five generations
CUMULATIVE INBREEDING COEFFICIENT – includes all inbreeding in the subject’s pedigree back as far as records allow

WRIGHT’S EQUATION FOR CALCULATING THE COEFFICIENT OF INBREEDING

As devised by Sewell Wright in 1922

Fx is the inbreeding coefficient of the horse in question, Fa is the inbreeding coefficient of the common ancestor, n1 is the number of generations from the sire to the common ancestor, and n2 is the number of generations from the dam to the common ancestor.


CEDRIC PHANTOM WALTON
Walton mare WALTON

Cedric is the result of the mating of half-sibs, both his parents being by Walton. If Walton carries a gene with two different alleles, the one which is passed to Phantom has a 50% probability of being passed to Cedric. There is also a 50% probability that the Walton mare will receive the same allele from Walton and a 50% probability of it being passed to Cedric. The probability that Cedric will be homozygous for this allele is 0.5 x 0.5 x 0.5 = 0.125 or 12.5%. If Walton were the only common ancestor, the inbreeding coefficient for Cedric would be 12.5%.
Simply put, Cedric’s inbreeding coefficient is found by calculating ½ to the power n, where n is the number of individuals from Cedric to the common ancestor Walton and back to Cedric on the other side of the pedigree, less Cedric. This makes n equal to Phantom – Walton – Walton mare, or 3. The calculation therefore is (½)³ or (½ x ½ x ½), which equals one eighth or 12.5%.
In the equation quoted above n1 = 1 (Phantom) and n2 = 1 (Walton mare). Walton, the common ancestor, is represented by 1. If Walton is also inbred, then Cedric’s inbreeding coefficient would be 12.5 x (1 plus the inbreeding coefficient of Walton, the common ancestor). If the common ancestor is not inbred then Fa = 0, therefore this part of the equation can be ignored because (1+Fa) = 1.
If Cedric had more than one common ancestor then calculations would be made for each and added together to give his inbreeding coefficient.

On the face of it Wright’s Equation works, however closer examination reveals inherent defects.

OMAR GODOLPHIN ARABIAN
Lath mare LATH GODOLPHIN ARABIAN

In the above pedigree Omar is inbred to Godolphin Arabian (1 x 3), so the value for n in the equation equals Godolphin Arabian – Lath – Lath mare or 3. This gives an inbreeding coefficient of 12.5%, the same as that for Cedric. The problem is Omar is more closely inbred than Cedric. Cedric inherited 25% of his genes from Walton through Phantom and 25% of his genes from Walton through Walton mare, making a total of 50%, which when divided by four gives an inbreeding coefficient of 12.5%. Omar, on the other hand, inherited 50% of his genes from Godolphin Arabian as his sire and 12.5% of his genes from Godolphin Arabian through Lath mare, making a total of 62.5%, which when divided by four gives an inbreeding coefficient of 15.625%.

The value of n in Wright’s Equation does not take into consideration the positions of the common ancestor in the pedigree.

If Cedric’s grandsire Walton was inbred to A (2 x 2), Cedric’s inbreeding coefficient would be .125 x 1.125 = .140625 or 14.0625%.The increase of 1.5625% represents the total influence of A which appears four times in the fourth generation of the pedigree of Cedric. Cedric inherited 25% of his genes from A, which when divided by four gives an inbreeding coefficient of 6.25%. Cedric’s inbreeding coefficient would therefore be 12.5% + 6.25% = 18.75%.
If Omar’s sire Godolphin Arabian was inbred to B (2 x 2), Omar’s inbreeding coefficient would also be .125 x 1.125 = .140625 or 14.0625%. The increase of 1.5625% represents the total influence of B which appears twice in the third generation and twice in the fifth generation of the pedigree of Omar. Omar inherited 25% of his genes from B in the third generation and 6.25% of his genes from B in the fifth generation, making a total of 31.25%, which when divided by four gives an inbreeding coefficient of 7.8125%. Omar’s inbreeding coefficient would therefore be 15.625% + 7.8125% = 23.4375%.

Multiplying an inbreeding coefficient by one plus the inbreeding coefficient of a common ancestor severely underestimates the total amount of inbreeding in a pedigree.

W E Jones in Genetics of the Horse makes the following statements concerning Wright’s Equation:

Page 189 – “To determine if there is any inbreeding, one observes the material on the sire’s side of the pedigree to see if any animal is common with what is on the dam’s side of the pedigree”.

Page 189 – “The amount of inbreeding is usually expressed in a percentage, which can be considered to be an estimate of the percentage of the total genes that have been put in the homozygous state. This estimate is always less than the actual because our records are never extensive enough to show all of the relationships that ever existed”.

Page 190 – “The equation for calculating the coefficent of inbreeding as proposed by Wright may look somewhat complicated to one without much background in mathematics. The coefficient of inbreeding is a fraction which when multiplied by 100 gives the percentage of inbreeding. The formula is based on the principle that the inbreeding of an individual is one half the relationship of its sire and dam”.

In fact, an inbreeding coefficient calculated using Wright’s Equation is neither an estimation of the number of genes put into the homozygous state nor an estimation of the percentage of inbreeding. It is merely the probability that identical alleles will be inherited from ancestors common to both sire and dam.

Wright’s Equation considers duplicated ancestors only if they are common to both sire and dam, but if the inbreeding of an individual is one half the relationship of its sire and dam, then duplicated ancestors wholly contained within the pedigrees of either the sire or the dam should also be considered because ultimately they will trace to ancestors common to both sire and dam. The following pedigree is an example:

HIGH BIRD
1933
HIGH TIME
1916
ULTIMUS
1906
COMMANDO
1898
DOMINO HIMYAR
Mannie Gray
Emma C DAREBIN
Guenn
Running Stream
1898
DOMINO HIMYAR
Mannie Gray
Dancing Water ISONOMY
Pretty Dance
Noonday
1898
DOMINO
1891
HIMYAR ALARM
Hira
Mannie Gray ENQUIRER
Lizzie G
Sundown
1887
SPRINGFIELD ST ALBANS
Viridis
Sunshine THORMANBY
Sunbeam
Billie Dove
1922
ATHELING
1913
DESMOND
1896
ST SIMON GALOPIN
St Angela
L’Abesse de Jouarre TRAPPIST
Festive
Wood Daisy
1906
CYLLENE BONA VISTA
Arcadia
Mountain Daisy AYRSHIRE
Light of Other Days
Polistena
1912
POLYMELUS
1902
CYLLENE BONA VISTA
Arcadia
Maid Marian HAMPTON
Quiver
Imola
1901
ST HILAIRE ST SIMON
Distant Shore
Yola BONA VISTA
Doralice

HIGH BIRD has no ancestors in the first five generations which are common to both sire and dam.

The sire HIGH TIME is inbred to DOMINO (3 x 3) x 2
The paternal grandsire ULTIMUS is inbred to DOMINO 2 x 2

The dam Billie Dove is inbred to CYLLENE 3 x 3, ST SIMON 3 x 4 and BONA VISTA 4 x (4 x 4)
The maternal grandam Polistena is inbred to BONA VISTA 3 x 3

The following inbreeding coefficients are produced by Wright’s Equation using only the information contained in this five generation pedigree:

HIGH BIRD = 0% HIGH TIME = 12.5% ULTIMUS = 12.5% Billie Dove = 6.25% Polistena = 3.125%

The inbreeding coefficient of 0% for HIGH BIRD produced by Wright’s Equation is impossible. If his pedigree is extended to nine generations the following ancestors are common to both sire and dam:

Banter (9 x 9 x 9 x 9 x 9) x (9 x 9 x 9 x 9 x 9 x 9 x 9 x 9 x 9)
BAY MIDDLETON (9 x 9 x 8 x 7) x (8 x 9 x 9)
BIRDCATCHER (8 x 9 x 9 x 9 x 8 x 7) x (8 x 9 x 9 x 9)
CAMEL (9 x 9 x 9 x 9 x 9 x 9) x (9 x 9 x 9 x 9 x 8 x 9 x 9)
CATTON 9 x 9
Cerberus mare (9 x 9) x 9
Decoy (9 x 8) x 8
DONCASTER 6 x (7 x 7 x 7)
ECONOMIST 9 x (8 x 9)
GLENCOE (9 x 9 x 9 x 9 x 9 x 9 x 9 x 8 x 9 x 9 x 8) x (8 x 9)
Guiccioli (9 x 9 x 9 x 8 x 9 x 8) x 9
ISONOMY 5 x (6 x 6)
KING TOM 8 x (6 x 8 x 8 x 7 x 8)
LANERCOST (9 x 9 x 8) x (9 x 8)
LOTTERY 8 x 9
MELBOURNE (7 x 9) x (9 x 8 x 8 x 9)
MULEY (9 x 9 x 8) x (9 x 9)
ORLANDO (8 x 8 x 9 x 7 x 7) x (9 x 9 x 8)
PALMYRA 7 x (9 x 9)
PANTALOON (9 x 9 x 9 x 9 x 8 x 8 x 7) x (9 x 9 x 9 x 8 x 9 x 9 x 9 x 9)
Pasquinade (9 x 8) x 9
Phryne 7 x 9
Pocahontas (9 x 9 x 9 x 8 x 8 x 8 x 7) x (7 x 9 x 9 x 9 x 9 x 9 x 9 x 9 x 9 x 8 x 9 x 9)
Rebecca 7 x 9
RIFLEMAN 9 x 8
SCOTTISH CHIEF 7 x 6
SIR HERCULES (9 x 9 x 9 x 8 x 9 x 8) x 9
STOCKWELL (8 x 8 x 7 x 7 x 7 x 6) x (8 x 8 x 9 x 8 x 8 x 8 x 8)
SULTAN (9 x 9 x 9 x 8 x 8) x (9 x 9)
TAURUS2 8 x 9
THE BARON (9 x 9 x 8 x 8 x 8 x 7) x (9 x 9 x 9 x 9 x 9 x 9 x 9)
THE FLYING DUTCHMAN 9 x (7 x 9 x 8)
THORMANBY (8 x 5) x (8 x 8 x 8 x 8 x 8)
TOUCHSTONE (9 x 8 x 9 x 9 x 9 x 9 x 8 x 8 x 8) x (8 x 8 x 9 x 9 x 9 x 9 x 8 x 9 x 8 x 9 x 8)
VELOCIPEDE 9 x 9
WHALEBONE (9 x 9) x 9
WHISKER (9 x 8) x 9

The method I am proposing produces the following inbreeding coefficients using only the information contained in this five generation pedigree:

HIGH BIRD = 18.75% HIGH TIME = 18.75% ULTIMUS = 12.5% Billie Dove = 18.75% Polistena = 6.25%


HARDIMAN’S METHOD FOR CALCULATING THE COEFFICIENT OF INBREEDING

As devised by James R Hardiman in 2000
CEDRIC PHANTOM (12.5%) WALTON (6.25%)
Walton mare (12.5%) WALTON (6.25%)

Cedric’s inbreeding coefficient of 12.5% is calculated for an ancestor which appears twice in the second generation of his pedigree, therefore each appearance in the second generation is worth 6.25%. The total for each generation is 25%, which is the probability of an allele being passed from Walton to Phantom to Cedric. Since the total for each generation is 25, the value for each position in the pedigree can be summarised as follows:

1st Generation = 12.5
2nd Generation= 6.25
3rd Generation = 3.125
4th Generation = 1.5625
5th Generation = .78125

There are 32 ancestors in the fifth generation, each contributing .78125 of the whole. Since at least two positions in the pedigree are required for inbreeding and the maximum of 25 cannot be reached, that leaves 30 possible basic inbreeding coefficients within five generations. Each basic coefficient, which is a multiple of .78125, represents the number of ancestors in the 5th generation that are contained within the pedigree of the common ancestor. It should be noted that there are many more combinations of inbreedings, but there are only 30 possible basic inbreeding coefficients.

Inbreeding notations
Basic coefficients
1 x 2 x 3 x 4 x 5 24.21875
1 x 2 x 3 x 4 23.4375
1 x 2 x 3 x 5 22.65625
1 x 2 x 3 21.875
1 x 2 x 4 x 5 21.09375
1 x 2 x 4 20.3125
1 x 2 x 5 19.53125
1 x 2 18.75
1 x 3 x 4 x 5 17.96875
1 x 3 x 4 17.1875
1 x 3 x 5 16.40625
1 x 3 15.625
1 x 4 x 5 14.84375
1 x 4 14.0625
1 x 5 13.28125
2 x 2 12.5
2 x 3 x 4 x 5 11.71875
2 x 3 x 4 10.9375
2 x 3 x 5 10.15625
2 x 3 9.375
2 x 4 x 5 8.59375
2 x 4 7.8125
2 x 5 7.03125
3 x 3 6.25
3 x 4 x 5 5.46875
3 x 4 4.6875
3 x 5 3.90625
4 x 4 3.125
4 x 5 2.34375
5 x 5 1.5625

The inbreeding coefficients have to be modified if the common ancestor is also inbred. The movement of an ancestor back one generation in a pedigree halves its influence, therefore the inbreeding coefficient of an inbred ancestor has to be halved to compensate. The value of an inbreeding coefficient for each generation is calculated as follows:

Generation 0 – Inbreeding Coefficient
Generation 1 – Divide by 2
Generation 2 – Divide by 4
Generation 3 – Divide by 8
Generation 4 – Divide by 16
Generation 5 – Divide by 32

0 1 2 3 4
D A B
C B
E A B
C B

In the above pedigree D is inbred to A (1 x 2). The inbreeding coefficient for D is therefore 12.5 + 6.25 = 18.75.
A, however, is inbred to B (1 x 2) and appears in two different generations. The inbreeding coefficient for A is also 18.75.
The movement of an ancestor back one generation in a pedigree halves its influence, so the modified coefficient for A in generation 1 will be 9.375 and in generation 2 it will be 4.6875. The influence of A in the pedigree is therefore 9.375 + 4.6875 = 14.0625. The inbreeding coefficient for D will be 18.75 + 14.0625 = 32.8125.
In the above pedigree B appears once in generation 2, twice in generation 3 and once in generation 4. The values for these positions in the pedigree are 6.25, 3.125, 3.125 and 1.5625. The addition of these figures gives 14.0625, which is the influence of A in the pedigree.


AN EXAMPLE OF THE CALCULATION OF A COEFFICIENT OF INBREEDING USING HARDIMAN’S METHOD

THE COMPLETE PEDIGREE OF JIGG-OF-JIGGS

This pedigree contains new and conjectural information of a radical nature – See

 Old Bald Peg = FAIRFAX'S MOROCCO BARB           MERLIN'S   =  Merlin's                 Barb Mare
              |    [HELMSLEY TURK]               GRANDSIRE  |  Grandam                      | 1665
              |          |                                  |                               |
       ----------------> | <------------------------------> | <---------------------------> | <------------------
       |                 |                                  |                               |                   |
       |                 --------                 -----------                               |                   |
       |                 |      |                 |                                         |                   |
Leedes Bald Peg          |   DIAMOND =           Mare                 Royal Mare = DARCY'S YELLOW TURK = Old Morocco Mare
[Young Bald Peg]         |           | [Sister to Merlin's dam]                  |     [DODSWORTH]     |        |
       |                 |           |                                           |                     |        |
       |                 |           ------------------------------------        |                     |        |
       |                 |                                              |        |                     |        |
  ------                 |                              --------------> | <----> | <--------------------        ------
  |                      |                              |               |        |                     |             |
  |             DARCY'S WHITE TURK       =    Darcy's Grey Royal       mare = BRIMMER               SPANKER          |
  |            [PLACE'S WHITE TURK]      |  [Lonsdale Arabian Mare]         |                          |             |
  |      [PLACE'S WHITE TRUGUNWELL TURK] |                                  |                          |             |
  |           [BURNET'S WHITE BARB]      |                                  |                          |             |
  |    --------------------------------> | <------------------------------> | <-------------------------             |
  |    |                                 |                                  |                          |             |
  |    |      -------------------------> | <---------------------------------                          |             |
  |    |      |                          |                                                             |             |
  |    |      |                 -----------------------------                                          |             |
     /       |                 |                           |                                                      /
   mare      mare  =         HAUTBOY          =      Darcy's Pet Mare         BYERLEY'S TURK     =     Charming Jenny
    |              |        [ROCKWOOD]        |      [Old Grey Royal]         [LISTER'S TURK]    |   [Wyvill's Roan Mare]
    |              | [PULLEINE'S WHITE TURK]  |   [Tregonwell Barb mare]    [RUTLAND BLACKLEGS]  |
    |              | [PULLEINE'S OLD ARABIAN] | [Darcy's Oldest Royal Mare]                      |
    |              |                          |        [Clubfoot]                                |
    |              ------             ----------------------                        -----------------------
    |                   |             |                    |                        |                     |
 Bay Peg               mare        CLUMSEY            Grey Wilkes      =      PELHAM'S JIGG        BROTHER TO SNAKE
by Leedes               |             |               [Old Wilkes]     |     [LISTER'S SNAKE]             |
 Arabian                |             |                                |            |                     |
    |                   |             |                                |            |                     |
    ------------------> | <--------   |                                |            |                     |
                        |           /                                 |            |                     |
BLUE CAP                |          FOX                                 |            |                    mare
    |                   |           | 1714                             |            |                     |
    |                   |           |                                  |            ---------     ---------
    |                   |           |                                  |                        /
   mare             CHAMPION        |                             SON OF JIGG       =        mare
    |          by Harpham Arabian   |                       [SMITH'S SON OF SNAKE]  |         |
    |                   | 1707      |                                               |         |
    ----------------    |           |                                               |         |
                      /            |                                               |         |
                    mare            |                                        HENEAGE'S JIGG   |
                      |             |                                               |         |
                      ----       ----                                               ---    ----
                               /                                                        /
                        BOLTON GOLIAH                       =                          mare
                                1730                        |                           |
                                                            |                           |
                                                            |                           |
                                                       HUNT'S JIGG                      |
                                                            | 1741                      |
                                                            --------             --------
                                                                               /
                                                                    JIGG-OF-JIGGS
                                                                            1745

Jigg-of-Jiggs is one of the most inbred horses in the General Stud Book and his inbreeding coefficient is calculated as follows:

0 1 2 3 4 5
JIGG-OF-JIGGS
21.875
39.208984375
52.34375
(113.427734375)
HUNT’S JIGG
03.515625
09.521484375
26.171875
(39.208984375)
BOLTON GOLIAH
03.125
05.859375
00.537109375
(09.521484375)
FOX
02.5390625
02.734375
00.5859375
(05.859375)
CLUMSEY
02.1484375
00.29296875
00.29296875
(02.734375)
HAUTBOY
(00.29296875)
Darcy’s Pet Mare
(00.29296875)
Bay Peg
(00.5859375)
LEEDES ARABIAN
Spanker mare
(00.5859375)
Champion mare
(00.537109375)
CHAMPION
(00.537109375)
HARPHAM ARABIAN
Hautboy mare
(00.537109375)
Blue Cap mare BLUE CAP
Heneage’s Jigg mare
(26.171875)
HENEAGE’S JIGG SON OF JIGG PELHAM’S JIGG
Grey Wilkes
Pelham’s Jigg mare
PELHAM’S JIGG
Brother to Snake mare
Pelham’s Jigg mare PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny
Brother to Snake mare BROTHER TO SNAKE
Heneage’s Jigg mare
26.5625
19.3359375
06.4453125
(52.34375)
HENEAGE’S JIGG
10.3515625
05.76171875
03.22265625
(19.3359375)
SON OF JIGG
02.44140625
00.5859375
02.734375
(05.76171875)
PELHAM’S JIGG
(00.5859375)
BYERLEY’S TURK
Charming Jenny
(00.5859375)
Grey Wilkes
02.1484375
00.29296875
00.29296875
(02.734375)
HAUTBOY
(00.29296875)
Darcy’s Pet Mare
(00.29296875)
Pelham’s Jigg mare
(03.22265625)
PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny
Brother to Snake mare BROTHER TO SNAKE
Pelham’s Jigg mare
04.6875
01.171875
00.5859375
(06.4453125)
PELHAM’S JIGG
(01.171875)
BYERLEY’S TURK
Charming Jenny
(01.171875)
SPANKER
Old Morocco Mare
Brother to Snake mare
(00.5859375)
BROTHER TO SNAKE
(00.5859375)
LISTER’S TURK
Charming Jenny
(00.5859375)
0 1 2 3 4 5

Details of each specific inbreeding:

JIGG-OF-JIGGS inbred to Heneage’s Jigg mare 2 x 1 = 18.75
JIGG-OF-JIGGS inbred to HAUTBOY 5 x 5 = 1.5625
JIGG-OF-JIGGS inbred to Darcy’s Pet Mare 5 x 5 = 1.5625
Total SIC for JIGG-OF-JIGGS = 21.875
HUNT’S JIGG inbred to HAUTBOY (4 x 5) x 5 = 3.125
HUNT’S JIGG inbred to Darcy’s Pet Mare 4 x 5 = 2.34375
HUNT’S JIGG inbred to SPANKER 5 x 5 = 1.5625
Total SIC for HUNT’S JIGG = 7.03125
Heneage’s Jigg mare inbred to Pelham’s Jigg mare 2 x 1 = 18.75
Heneage’s Jigg mare inbred to PELHAM’S JIGG (3 x 3) x 2 = 12.5
Heneage’s Jigg mare inbred to BYERLEY’S TURK=LISTER’S TURK (4 x 4 x 5) x (3 x 4) = 8.59375
Heneage’s Jigg mare inbred to Charming Jenny (4 x 4 x 5) x (3 x 4) = 8.59375
Heneage’s Jigg mare inbred to Old Morocco Mare (5 x 5) x (5 x 4 x 5) = 4.6875
Total SIC for Heneage’s Jigg mare = 53.125
BOLTON GOLIAH inbred to HAUTBOY 3 x 4 = 4.6875
BOLTON GOLIAH inbred to DARCY’S WHITE TURK (4 x 4) x 5 = 3.90625
BOLTON GOLIAH inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare (4 x 4) x 5 = 3.90625
Total SIC for BOLTON GOLIAH = 12.5
HENEAGE’S JIGG inbred to PELHAM’S JIGG 2 x 2 = 12.5
HENEAGE’S JIGG inbred to BYERLEY’S TURK=LISTER’S TURK 3 x (3 x 4) = 7.8125
HENEAGE’S JIGG inbred to Charming Jenny 3 x (3 x 4) = 7.8125
HENEAGE’S JIGG inbred to Old Morocco Mare (5 x 4 x 5 x 5) x (5 x 4 x 5) = 7.03125
HENEAGE’S JIGG inbred to DARCY’S YELLOW TURK (5 x 5 x 5) x 5 = 3.125
HENEAGE’S JIGG inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (5 x 5 x 5) x 5 = 3.125
Total SIC for HENEAGE’S JIGG = 41.40625
Pelham’s Jigg mare inbred to BYERLEY’S TURK=LISTER’S TURK 2 x 3 = 9.375
Pelham’s Jigg mare inbred to Charming Jenny 2 x 3 = 9.375
Total SIC for Pelham’s Jigg mare = 18.75
FOX inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (4 x 5 x 4 x 5) x (5 x 4) = 7.03125
FOX inbred to DARCY’S YELLOW TURK (4 x 4) x 4 = 4.6875
FOX inbred to Old Morocco Mare (4 x 4) x 4 = 4.6875
FOX inbred to Old Bald Peg (5 x 5) x (5 x 4) = 3.90625
Total SIC for FOX = 20.3125
SON OF JIGG inbred to Old Morocco Mare (4 x 3) x (4 x 4) = 7.8125
SON OF JIGG inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (5 x 4) x (4 x 5 x 4 x 5) = 7.03125
SON OF JIGG inbred to DARCY’S YELLOW TURK 4 x (4 x 4) = 4.6875
Total SIC for SON OF JIGG = 19.53125
CLUMSEY inbred to DARCY’S WHITE TURK 2 x 2 = 12.5
CLUMSEY inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare 2 x 2 = 12.5
CLUMSEY inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x (3 x 4) = 9.375
Total SIC for CLUMSEY = 34.375
Grey Wilkes inbred to DARCY’S WHITE TURK 2 x 2 = 12.5
Grey Wilkes inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare 2 x 2 = 12.5
Grey Wilkes inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x (3 x 4) = 9.375
Total SIC for Grey Wilkes = 34.375
Charming Jenny inbred to Old Morocco Mare 2 x 1 = 18.75
Total SIC for Charming Jenny = 18.75
HAUTBOY inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK 2 x 3 = 9.375
Total SIC for HAUTBOY = 9.375
Darcy’s Pet Mare inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK 2 x 3 = 9.375
Total SIC for Darcy’s Pet Mare = 9.375
Spanker mare inbred to FAIRFAX’S MOROCCO BARB 3 x 2 = 9.375
Spanker mare inbred to Old Bald Peg 3 x 2 = 9.375
Total SIC for Spanker mare = 18.75
Hautboy mare inbred to DARCY’S YELLOW TURK 3 x 3 = 6.25
Hautboy mare inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x 4 = 6.25
Total SIC for Hautboy mare = 12.5

METHOD ONE
Working forwards through the pedigree

6 HAUTBOY = modified SIC of 0.146484375
5 HAUTBOY = modified SIC of 0.29296875
5 Darcy’s Pet Mare = modified SIC of 0.29296875
5 Spanker mare = modified SIC of 0.5859375
5 Hautboy mare = modified SIC of 0.390625 + modified SIC for HAUTBOY in generation 6 of 0.146484375 = 0.537109375
5 Charming Jenny = modified SIC of 0.5859375
4 CLUMSEY = modified SIC of 2.1484375 + modified SIC for HAUTBOY in generation 5 of 0.29296875 + modified SIC for Darcy’s Pet Mare in generation 5 of 0.29296875 = 2.734375
4 Bay Peg = modified SIC for Spanker mare in generation 5 of 0.5859375
4 PELHAM’S JIGG = modified SIC for Charming Jenny in generation 5 of 0.5859375
4 Grey Wilkes = modified SIC of 2.1484375 + modified SIC for HAUTBOY in generation 5 of 0.29296875 + modified SIC for Darcy’s Pet Mare in generation 5 of 0.29296875 = 2.734375
4 Charming Jenny = modified SIC of 1.171875
3 FOX = modified SIC of 2.5390625 + modified CIC for CLUMSEY in generation 4 of 2.734375 + modified CIC for Bay Peg in generation 4 of 0.5859375 = 5.859375
3 Champion mare = modified SIC for Hautboy mare in generation 5 of 0.537109375
3 SON OF JIGG = modified SIC of 2.44140625 + modified CIC for PELHAM’S JIGG in generation 4 of 0.5859375 + modified CIC for Grey Wilkes in generation 4 of 2.734375 = 5.76171875
3 Pelham’s Jigg mare = half the modified CIC for Pelham’s Jigg mare in generation 2 of 6.4453125 = 3.22265625
3 PELHAM’S JIGG = modified SIC for Charming Jenny in generation 4 of 1.171875
3 Brother to Snake mare = modified SIC for Charming Jenny in generation 5 of 0.5859375
2 BOLTON GOLIAH = modified SIC of 3.125 + modified CIC for FOX in generation 3 of 5.859375 + modified CIC for Champion mare in generation 3 of 0.537109375 = 9.521484375
2 Heneage’s Jigg mare = half the modified CIC in generation 1 of 52.34375 = 26.171875
2 HENEAGE’S JIGG = modified SIC of 10.3515625 + modified CIC for SON OF JIGG in generation 3 of 5.76171875 + modified CIC for Pelham’s Jigg mare in generation 3 of 3.22265625 = 19.3359375
2 Pelham’s Jigg mare = modified SIC of 4.6875 + modified CIC for PELHAM’S JIGG in generation 3 of 1.171875 + modified CIC for Brother to Snake mare in generation 3 of 0.5859375 = 6.4453125
1 HUNT’S JIGG = modified SIC of 3.515625 + modified CIC for BOLTON GOLIAH in generation 2 of 9.521484375 + modified CIC for Heneage’s Jigg mare in generation 2 of 26.171875 = 39.208984375
1 Heneage’s Jigg mare = modified SIC of 26.5625 + modified CIC for HENEAGE’S JIGG in generation 2 of 19.3359375 + modified CIC for Pelham’s Jigg mare in generation 2 of 6.4453125 = 52.34375
0 JIGG-OF-JIGGS = SIC of 21.875 + modified CIC for HUNT’S JIGG in generation 1 of 39.208984375 + modified CIC for Heneage’s Jigg mare in generation 1 of 52.34375 = 113.427734375

METHOD TWO
Working backwards through the pedigree

Inbred Horse SIC Modified SIC
0 JIGG-OF-JIGGS 21.875 21.875
1 HUNT’S JIGG 7.03125 ÷ 2 03.515625
1 Heneage’s Jigg mare 53.125 ÷ 2 26.5625
2 BOLTON GOLIAH 12.5 ÷ 4 03.125
2 Heneage’s Jigg mare 53.125 ÷ 4 13.28125
2 HENEAGE’S JIGG 41.40625 ÷ 4 10.3515625
2 Pelham’s Jigg mare 18.75 ÷ 4 04.6875
3 FOX 20.3125 ÷ 8 02.5390625
3 HENEAGE’S JIGG 41.40625 ÷ 8 05.17578125
3 Pelham’s Jigg mare 18.75 ÷ 8 02.34375
3 SON OF JIGG 19.53125 ÷ 8 02.44140625
3 Pelham’s Jigg mare 18.75 ÷ 8 02.34375
4 CLUMSEY 34.375 ÷ 16 02.1484375
4 SON OF JIGG 19.53125 ÷ 16 01.220703125
4 Pelham’s Jigg mare 18.75 ÷ 16 01.171875
4 Grey Wilkes 34.375 ÷ 16 02.1484375
4 Charming Jenny 18.75 ÷ 16 01.171875
5 HAUTBOY 9.375 ÷ 32 00.29296875
5 Darcy’s Pet Mare 9.375 ÷ 32 00.29296875
5 Spanker mare 18.75 ÷ 32 00.5859375
5 Hautboy mare 12.5 ÷ 32 00.390625
5 Grey Wilkes 34.375 ÷ 32 01.07421875
5 Charming Jenny 18.75 ÷ 32 00.5859375
5 Charming Jenny 18.75 ÷ 32 00.5859375
5 HAUTBOY 9.375 ÷ 32 00.29296875
5 Darcy’s Pet Mare 9.375 ÷ 32 00.29296875
5 Charming Jenny 18.75 ÷ 32 00.5859375
5 Charming Jenny 18.75 ÷ 32 00.5859375
6 HAUTBOY 9.375 ÷ 64 00.146484375
6 Charming Jenny 18.75 ÷ 64 00.29296875
6 HAUTBOY 9.375 ÷ 64 00.146484375
6 Darcy’s Pet Mare 9.375 ÷ 64 00.146484375
6 Charming Jenny 18.75 ÷ 64 00.29296875
6 Charming Jenny 18.75 ÷ 64 00.29296875
6 Charming Jenny 18.75 ÷ 64 00.29296875
7 Charming Jenny 18.75 ÷ 128 00.146484375
Total CIC for JIGG-OF-JIGGS 113.427734375

METHOD THREE
Register of Inbreeding Coefficients

The figure of 113.427734375, arrived at by both Method One and Method Two above, is the cumulative inbreeding coefficent for Jigg-of-Jiggs and includes all the inbreeding in his pedigree back as far as records allow. The standard inbreeding coefficient for Jigg-of-Jiggs of 21.875 is a fifth of this total, so it is clear that the inbreeding carried forward from previous generations is still valid but the methods of calculation are cumbersome and time consuming.

It is proposed that a Register of Inbreeding Coefficients of all stallions and mares be compiled, so that any Thoroughbred’s cumulative inbreeding coefficient may be found by first calculating the standard inbreeding coefficient and adding to it half the value of each of the parents cumulative inbreeding coefficients as taken from the register.

Using this method and beginning with the earliest inbred ancestor, the cumulative inbreeding coefficient for Jigg-of-Jiggs would be calculated as follows:

Charming Jenny
(18.75)
SPANKER
(0)
Old Morocco Mare
Old Morocco Mare
(0)

Charming Jenny inbred to Old Morocco Mare 2 x 1 = 18.75
Total SIC and CIC for Charming Jenny = 18.75


Spanker mare
(18.75)
SPANKER
(0)
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Old Bald Peg
Leedes Bald Peg
(0)
FAIRFAX’S MOROCCO BARB
Old Bald Peg

Spanker mare inbred to FAIRFAX’S MOROCCO BARB 3 x 2 = 9.375
Spanker mare inbred to Old Bald Peg 3 x 2 = 9.375
Total SIC and CIC for Spanker mare = 18.75


HAUTBOY
(09.375)
DARCY’S WHITE TURK
(0)
HELMSLEY TURK
Lonsdale Arabian Mare
(0)
Old Morocco Mare FAIRFAX’S MOROCCO BARB

HAUTBOY inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK 2 x 3 = 9.375
Total SIC and CIC for HAUTBOY = 9.375


Darcy’s Pet Mare
(09.375)
DARCY’S WHITE TURK
(0)
HELMSLEY TURK
Darcy’s Grey Royal
(0)
Old Morocco Mare FAIRFAX’S MOROCCO BARB

Darcy’s Pet Mare inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK 2 x 3 = 9.375
Total SIC and CIC for Darcy’s Pet Mare = 9.375


CLUMSEY
(43.75)
HAUTBOY
(09.375)
DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Darcy’s Pet Mare
(09.375)
DARCY’S WHITE TURK HELMSLEY TURK
Darcy’s Grey Royal
Old Morocco Mare FAIRFAX’S MOROCCO BARB

CLUMSEY inbred to DARCY’S WHITE TURK 2 x 2 = 12.5
CLUMSEY inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare 2 x 2 = 12.5

CLUMSEY inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x (3 x 4) = 9.375
Total SIC for CLUMSEY = 34.375
Half CIC for HAUTBOY = 4.6875
Half CIC for Darcy’s Pet Mare = 4.6875
Total CIC for CLUMSEY = 43.75


Grey Wilkes
(43.75)
HAUTBOY
(09.375)
DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Darcy’s Pet Mare
(09.375)
DARCY’S WHITE TURK HELMSLEY TURK
Darcy’s Grey Royal
Old Morocco Mare FAIRFAX’S MOROCCO BARB

Grey Wilkes inbred to DARCY’S WHITE TURK 2 x 2 = 12.5
Grey Wilkes inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare 2 x 2 = 12.5

Grey Wilkes inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x (3 x 4) = 9.375
Total SIC for Grey Wilkes = 34.375
Half CIC for HAUTBOY = 4.6875
Half CIC for Darcy’s Pet Mare = 4.6875
Total CIC for Grey Wilkes = 43.75


Hautboy mare
(17.1875)
HAUTBOY
(09.375)
DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Brimmer mare
(0)
BRIMMER DARCY’S YELLOW TURK
Diamond mare DIAMOND HELMSLEY TURK

Hautboy mare inbred to DARCY’S YELLOW TURK 3 x 3 = 6.25
Hautboy mare inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (3 x 4) x 4 = 6.25
Total SIC for Hautboy mare = 12.5
Half CIC for HAUTBOY = 4.6875
Total CIC for Hautboy mare = 17.1875


SON OF JIGG
(46.09375)
PELHAM’S JIGG
(9.375)
Charming Jenny
(18.75)
SPANKER DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Grey Wilkes
(43.75)
HAUTBOY DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Darcy’s Pet Mare DARCY’S WHITE TURK HELMSLEY TURK
Darcy’s Grey Royal DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB

SON OF JIGG inbred to Old Morocco Mare (4 x 3) x (4 x 4) = 7.8125
SON OF JIGG inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (5 x 4) x (4 x 5 x 4 x 5) = 7.03125
SON OF JIGG inbred to DARCY’S YELLOW TURK 4 x (4 x 4) = 4.6875
Total SIC for SON OF JIGG = 19.53125
Half CIC for PELHAM’S JIGG = 4.6875
Half CIC for Grey Wilkes = 21.875
Total CIC for SON OF JIGG = 46.09375


Pelham’s Jigg mare
(25.78125)
PELHAM’S JIGG
(9.375)
BYERLEY’S TURK
Charming Jenny
(18.75)
Brother to Snake mare
(4.6875)
BROTHER TO SNAKE
(9.375)
LISTER’S TURK
Charming Jenny
(18.75)

Pelham’s Jigg mare inbred to BYERLEY’S TURK=LISTER’S TURK 2 x 3 = 9.375
Pelham’s Jigg mare inbred to Charming Jenny 2 x 3 = 9.375
Total SIC for Pelham’s Jigg mare = 18.75
Half CIC for PELHAM’S JIGG = 4.6875
Half CIC for Brother to Snake mare = 2.34375
Total CIC for Pelham’s Jigg mare = 25.78125


FOX
(46.875)
CLUMSEY
(43.75)
HAUTBOY DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Old Bald Peg
Darcy’s Pet Mare DARCY’S WHITE TURK HELMSLEY TURK
Darcy’s Grey Royal DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Old Bald Peg
Bay Peg
(9.375)
Spanker mare
(18.75)
SPANKER DARCY’S YELLOW TURK
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Old Bald Peg
Leedes Bald Peg FAIRFAX’S MOROCCO BARB
Old Bald Peg

FOX inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (4 x 5 x 4 x 5) x (5 x 4) = 7.03125
FOX inbred to DARCY’S YELLOW TURK (4 x 4) x 4 = 4.6875
FOX inbred to Old Morocco Mare (4 x 4) x 4 = 4.6875
FOX inbred to Old Bald Peg (5 x 5) x (5 x 4) = 3.90625
Total SIC for FOX = 20.3125
Half CIC for CLUMSEY = 21.875
Half CIC for Bay Peg = 4.6875
Total CIC for FOX = 46.875


HENEAGE’S JIGG
(77.34375)
SON OF JIGG
(46.09375)
PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny SPANKER DARCY’S YELLOW TURK
Old Morocco Mare
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Grey Wilkes HAUTBOY DARCY’S WHITE TURK HELMSLEY TURK
Lonsdale Arabian Mare DARCY’S YELLOW TURK
Old Morocco Mare
Darcy’s Pet Mare DARCY’S WHITE TURK HELMSLEY TURK
Darcy’s Grey Royal DARCY’S YELLOW TURK
Old Morocco Mare
Pelham’s Jigg mare
(25.78125)
PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny SPANKER DARCY’S YELLOW TURK
Old Morocco Mare
Old Morocco Mare FAIRFAX’S MOROCCO BARB
Brother to Snake mare BROTHER TO SNAKE LISTER’S TURK
Charming Jenny
Old Morocco Mare

HENEAGE’S JIGG inbred to PELHAM’S JIGG 2 x 2 = 12.5
HENEAGE’S JIGG inbred to BYERLEY’S TURK=LISTER’S TURK 3 x (3 x 4) = 7.8125
HENEAGE’S JIGG inbred to Charming Jenny 3 x (3 x 4) = 7.8125
HENEAGE’S JIGG inbred to Old Morocco Mare (5 x 4 x 5 x 5) x (5 x 4 x 5) = 7.03125
HENEAGE’S JIGG inbred to DARCY’S YELLOW TURK (5 x 5 x 5) x 5 = 3.125
HENEAGE’S JIGG inbred to FAIRFAX’S MOROCCO BARB=HELMSLEY TURK (5 x 5 x 5) x 5 = 3.125
Total SIC for HENEAGE’S JIGG = 41.40625
Half CIC for SON OF JIGG = 23.046875
Half CIC for Pelham’s Jigg mare = 12.890625
Total CIC for HENEAGE’S JIGG = 77.34375


BOLTON GOLIAH
(38.0859375)
FOX
(46.875)
CLUMSEY HAUTBOY DARCY’S WHITE TURK
Lonsdale Arabian Mare
Darcy’s Pet Mare DARCY’S WHITE TURK
Darcy’s Grey Royal
Champion mare
(4.296875)
CHAMPION
(8.59375)
Hautboy mare
(17.1875)
HAUTBOY DARCY’S WHITE TURK
Lonsdale Arabian Mare

BOLTON GOLIAH inbred to HAUTBOY 3 x 4 = 4.6875
BOLTON GOLIAH inbred to DARCY’S WHITE TURK (4 x 4) x 5 = 3.90625
BOLTON GOLIAH inbred to Darcy’s Grey Royal=Lonsdale Arabian Mare (4 x 4) x 5 = 3.90625
Total SIC for BOLTON GOLIAH = 12.5
Half CIC for FOX = 23.4375
Half CIC for Champion mare = 2.1484375
Total CIC for BOLTON GOLIAH = 38.0859375


Heneage’s Jigg mare
(104.6875)
HENEAGE’S JIGG
(77.34375)
SON OF JIGG PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny
Old Morocco Mare
Pelham’s Jigg mare PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny
Old Morocco Mare
Brother to Snake mare BROTHER TO SNAKE LISTER’S TURK
Charming Jenny
Pelham’s Jigg mare
(25.78125)
PELHAM’S JIGG BYERLEY’S TURK
Charming Jenny SPANKER
Old Morocco Mare
Old Morocco Mare
Brother to Snake mare BROTHER TO SNAKE LISTER’S TURK
Charming Jenny
Old Morocco Mare

Heneage’s Jigg mare inbred to Pelham’s Jigg mare 2 x 1 = 18.75
Heneage’s Jigg mare inbred to PELHAM’S JIGG (3 x 3) x 2= 12.5
Heneage’s Jigg mare inbred to BYERLEY’S TURK=LISTER’S TURK (4 x 4 x 5) x (3 x 4) = 8.59375
Heneage’s Jigg mare inbred to Charming Jenny (4 x 4 x 5) x (3 x 4) = 8.59375
Heneage’s Jigg mare inbred to Old Morocco Mare (5 x 5) x (5 x 4 x 5) = 4.6875
Total SIC for Heneage’s Jigg mare = 53.125
Half CIC for HENEAGE’S JIGG = 38.671875
Half CIC for Pelham’s Jigg mare = 12.890625
Total CIC for Heneage’s Jigg mare = 104.6875


HUNT’S JIGG
(78.41796875)
BOLTON GOLIAH
(38.0859375)
FOX CLUMSEY HAUTBOY
Darcy’s Pet Mare
Bay Peg
Spanker mare SPANKER
Champion mare CHAMPION
Hautboy mare HAUTBOY
Heneage’s Jigg mare
(104.6875)
HENEAGE’S JIGG SON OF JIGG
Grey Wilkes HAUTBOY
Darcy’s Pet Mare
Pelham’s Jigg mare PELHAM’S JIGG
Charming Jenny SPANKER

HUNT’S JIGG inbred to HAUTBOY (4 x 5) x 5 = 3.125
HUNT’S JIGG inbred to Darcy’s Pet Mare 4 x 5 = 2.34375
HUNT’S JIGG inbred to SPANKER 5 x 5 = 1.5625
Total SIC for HUNT’S JIGG = 7.03125
Half CIC for BOLTON GOLIAH = 19.04296875
Half CIC for Heneage’s Jigg mare = 52.34375
Total CIC for HUNT’S JIGG = 78.41796875


JIGG-OF-JIGGS
(113.427734375)
HUNT’S JIGG
(78.41796875)
BOLTON GOLIAH FOX CLUMSEY HAUTBOY
Darcy’s Pet Mare
Heneage’s Jigg mare
Heneage’s Jigg mare
(104.6875)
HENEAGE’S JIGG SON OF JIGG
Grey Wilkes HAUTBOY
Darcy’s Pet Mare

JIGG-OF-JIGGS inbred to Heneage’s Jigg mare 2 x 1 = 18.75
JIGG-OF-JIGGS inbred to HAUTBOY 5 x 5 = 1.5625
JIGG-OF-JIGGS inbred to Darcy’s Pet Mare 5 x 5 = 1.5625
Total SIC for JIGG-OF-JIGGS = 21.875
Half CIC for HUNT’S JIGG = 39.208984375
Half CIC for Heneage’s Jigg mare = 52.34375
Total CIC for JIGG-OF-JIGGS = 113.427734375


resource: www.highflyer.supanet.com


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