For the "diehards" this is worth reading.....maybe even studing!

[Insider 5,097]

Friday

I must begin with a confession. Before I could afford to breed even National Hunt racehorses, I sublimated my thoroughbred aspirations by breeding and showing guinea-pigs (cavies). Being competitive, I chose the breed that generated not only the most competition but was also most likely to win Best-In-Show (BIS) awards (short-haired Self Blacks).  I paid more than I really should for my initial stock, most costing the equivalent of £200 each today; but these consisted of successful show winners. Later additions sprung from the same foundation stock.  The approach worked, and my stock won over 100 BIS awards, including numerous ‘Cavy Classics’. Inevitably, animals produced from a largely ‘closed’ stud were related; but the inevitable inbreeding helped establish quality – as well as producing the odd less desirable side-effect such as some youngsters born with crooked legs. Nonetheless, when I began studying thoroughbred breeding seriously, my expectation was that inbreeding was likely to be an important factor in producing good racehorses.  This article seeks to examine whether this is or is not the case.  Of course, the thoroughbred too is a closed breed, with today’s horses coming from a small number (perhaps 100 or so) animals that were in existence 400 years ago; so a significant degree of inbreeding is inevitable. However, the question I address is whether much closer forms of inbreeding, in which the same animal is seen two or three times in a four-generation pedigree, is a help or hindrance in producing successful racehorses. First, though, we need to define some terms. 2x3 inbreeding involves inbreeding to a common ancestor in the second and third generations of a pedigree; 3x3 involves two duplications in the third generation; while with 2x4 inbreeding the common ancestor is found in the second and fourth generations. Successful examples of each are Enable (3x2 to Sadler’s Wells), Danehill (3x3 to Natalma) and Spinning World (2x4 to Northern Dancer).  These are the closest levels of inbreeding likely to be encountered in today’s thoroughbreds. My intention is to indicate whether horses bred thus have better or worse levels of racing ability than those with lower levels of inbreeding (3x4, 4x4 or 3x5), or with none at all within four generations. The problem with trying to answer a question like this is that it cannot be done by talking about one or two horses. Genetic variability in the thoroughbred is simply too great, as shown by my favourite example: two bay colts by a great stallion out of an outstanding racemare and broodmare, born in 1998 and 2000 respectively at the same stud and presumably brought up in the same way. One proved to be a fairly good racehorse and stallion: his name was Galileo. The other was unraced and infertile: he was called Atticus.  This variability means that, unless the results of any small sample of horses provide remarkable consistency, you need a fairly large sample of horses before you know whether you have a meaningful result. A random selection of ten inbred horses who were all found to have won Group 1s would be meaningful; if only one did, it wouldn’t. The need for large samples is definitely the case when it comes to the effects of close (2x3, 3x3, 2x4) inbreeding!  The study This means that for someone like me, whose OCD is demonstrated by a strange compulsion to study actual data before I express an opinion on breeding thoroughbreds, the collection of large enough samples involves considerable time and effort. This is followed by a few enjoyable days when the results can be analysed, the facts ascertained and the story told.  This particular study (here comes the boring bit) involved the identification of samples of very close (2x3) and close inbreeding (3x3, 2x4) in progeny selected from all 36,161 runners from 124 stallions in the top 50 per cent of sires ranked by the RPRs of their offspring.  The pedigrees of these animals were checked against the ‘Thoroughbred Pedigree Query’ database, with omissions from this database referenced on the Weatherbys website, in order to identify the closest inbreeding of 4x4 or equivalent. Two examples of inbreeding to the same ancestor found in the same generation of the pedigree were treated as the equivalent of a single example of inbreeding one generation closer, e.g. a case of 3 x (4x4) inbreeding to Northern Dancer is treated as equivalent to 3x3.  Whilst this data generated a total of 1,813 examples of 3x3 or 2x4 inbreeding, it only came up with 161 2x3 inbred animals, which was rather too small a sample. Accordingly, extra data was obtained by considering the sires and broodmare sires of runners by different stallions used in other studies. This increased the sample size to 331 examples of 2x3 inbreeding. Of these, 241 had same-sex siblings by other stallions born within three years of the inbred horse but not themselves closely inbred, this being an important means of assessing the effect of the inbreeding, as described below.  Findings The first indication of the impact of inbreeding was given by comparing the RPRs of closely-inbred horses with the average RPRs for all runners by their sires, the vast majority of which were not closely inbred. The results were:  Mean RPR of 241 2x3 inbred runners = 67.0 vs Mean of Average RPRs of sires of these runners = 72.0: exact difference = -4.98lb Mean RPR of 1,813 3x3 / 2x4 inbred runners = 75,7 vs Mean of Average RPRs of sires of these runners = 77.3: exact difference = -1.63lb Clearly, the closely inbred horses produced inferior results to those normally obtained from their sires.  However, there is a possibility that such close inbreeding was used by breeders in the hope of offsetting some perceived weakness in their mares, so perhaps the results arose because the mares were simply inferior. To check this possibility, I looked at results for ‘the closest independent sibling’ of each inbred horse, this being a horse of the same sex born within three years of the inbred animal and closest in age, but themselves not inbred closely. These were:   Mean RPR of siblings of 2x3 inbred runners = 71,7 vs Mean of Average RPRs of sires of these runners = 71.3, exact difference = +0.36lb Mean RPR of siblings of 3x3, 2x4 inbred runners = 74.5 vs Mean of Average RPRs of sires of these runners = 74.1, exact difference = +0.37lb So, basically the inferior results of neither group of inbred horses were due to the inferior quality of their dams. As compared with their closest independent siblings the animals inbred 2x3 and 3x3/2x4 were 5.34lb and 2.00lb worse racehorses.  For those readers interested in such matters, my computations suggest that the probability of these differences occurring purely by chance are less than one in 100 and three in 100 respectively, which makes ‘bad luck’ a somewhat unlikely explanation.  As a further check on the results, I also looked at the proportion of inbred horses whose ratings placed them in the top ten per cent and top 25 per cent of their sires’ runners ranked by RPR. Both of these were well below ten per cent and 25 per cent respectively (2x3: 5.8 per cent and 15.8 per cent respectively; 3x3/2x4: 8.5 per cent and 22.3 per cent), again indicating inferior outcomes for inbred horses.  Finally, I considered these same figures for horses who were inbred less closely and those not inbred within four generations. The full results were:

In top ten per cent of sire’s runners: 2x3: 5.8 per cent, 3x3/2x4: 8,5 per cent, 3x4/2x5: 9.3 per cent, 4x4/3x5: 10.2 per cent, No I/B: 10.4 per cent                                                                                     In top 25 per cent of sire’s runners:                                           2x3: 15.8 per cent, 3x3/2x4: 22.3 per cent, 3x4/2x5: 24.0 per cent, 4x4/3x5: 25.4 per cent, No I/B: 25.8 per cent The probability of both ‘top ten per cent’ and ‘top 10-25 per cent’ results for each of four samples being worse than those for the nearest less closely inbred sample is circa one in 28 = 0.0039, less than four in 1,000.  ‘The closer the inbreeding, the worse the results’ seems to be the clear message emanating from every one of these statistics. So, what might be the cause? One possible explanation may be that results are dominated by inbreeding to particular stallions that carry (and so pass on) weaknesses.  Within the 36,161 animals considered in the full study, 42 per cent of horses were inbred within four generations, of which Northern Dancer was the most commonly encountered subject of inbreeding with almost three-fifths involving him.  However, overall, the record of horses so inbred was slightly better than those of horses inbred to other sires; and there was no pattern of consistent over- or under-performance for any sire used as the basis for inbreeding. Choice of the subject for inbreeding did not materially affect its results.  In similar vein, I found no evidence that the means of inbreeding, whether resulting from the usual inbreeding to a stallion via his sons, inbreeding to a mare, or ‘opposite sex’ inbreeding via both sons and daughters of an ancestor, was significant – though in the last two cases samples were rather small. Accordingly, the probability is that inbreeding itself is the major cause of the generally inferior racing ability of closely-inbred animals. Consideration of elementary genetics suggests why this might be. Why does inbreeding affect racing ability? If inherited racing ability were a relatively simple attribute, rather than the result of a complex interaction of multiple genetic factors, inbreeding might be expected to produce generally beneficial effects. This approach proves successful in other forms of livestock breeding where appearance is vital (as for the cavies I used to breed), where the aim is to control a small number of relatively simple physical characteristics such as colour, coat and shape.  However, the racing aptitude of a horse is not readily controllable in this way. It arises from a complex combination of many genetic factors, including those affecting multiple facets of conformation and muscle development; internal organs such as heart, lungs and blood vessels; and the invisible but vital aspects of temperament and determination.  The genetic influences that have to be the ‘right’ ones in a top-class racehorse inevitably depend most heavily on co-dominant or recessive forms of genes (known as ‘alleles’), for which two identical copies of the allele are required to produce the desired factor. If these factors were produced by dominant alleles, then after 30+ generations of selective breeding they should by now be present in the entire thoroughbred population!  This means that any harmful recessive alleles that might inhibit racing ability when found in ‘double dosage’ (homozygous form), which are inevitably carried in ‘single dosage’ (heterozygous form) even by a horse such as Northern Dancer, could be duplicated by inbreeding, so that the undesirable element appears in the inbred horse along with the rather more desirable duplications that are beneficial to athletic ability. The inferior results of closely inbred animals probably arise from this effect. For each such negative allele held in the heterozygous form in the common ancestor, there is a 1 in 32 (3.13 per cent) chance that it will occur in homozygous form in the 2x3 inbred animal, and a 1 in 64 (1.56 per cent) chance in the 3x3 inbred.  These odds are just for one allele of one gene; and there may be a multiplicity of alleles that could produce adverse impacts on racing performance, e.g. a tendency to bleed into the lungs during vigorous exercise; breathing problems of various types; weaknesses in tendons or joints; inadequate bone density; over-excitability; lack of determination etc.   If these problems are caused by recessive alleles (which is the most likely scenario since selection against affected animals would quickly eliminate them from the population if they arose from dominant ones), then several might be hidden within the gene-pairs of even the finest animal.  Their effects would then emerge only when homozygosity is produced by inbreeding to him or her. A small number of such 3.13 per cent or 1.56 per cent chances would quickly account for the relative weakness in results found in closely-inbred horses.    There is no evidence, either in genetic theory or these results, for the proposition sometimes suggested that ‘prepotent’ ancestors might in some miraculous way pass on their superior ability when they are the subjects of inbreeding. If it exists at all in a creature as complex as the thoroughbred, prepotency is one generation deep! Similarly, I struggle to see arguments made by some (a polite way of saying I think they are rubbish) that more remote ‘line breeding’ is responsible for the ability of numerous top horses even if closer inbreeding may be unhelpful. This was once suggested by a bloodstock writer on the basis that a ‘line-bred’ pedigree, involving multiple crosses of a remote ancestor in more distant generations, is preferable to an ‘inbred’ one with fewer such crosses close up, since the additional intervening generations allow ‘the weeding out of negative influences.’ However, if such influences arise from dominant alleles of a gene a single generation would be sufficient to ‘weed them out’ by selection; but recessive alleles can stay hidden through several intermediate generations, with no means of ‘weeding them out’. It is then perfectly possible that, when the line-bred animal is produced, these alleles are brought together in homozygous form and therefore expressed.  The tendency of many thoroughbreds to suffer from burst blood vessels, when they are placed under stress by vigorous exercise or racing, is widely attributed to the influence of Hermit, who was an outstanding stallion despite being a known ‘bleeder’. Hermit was born in 1864. It is perfectly possible that multiple line-breeding to Hermit (via numerous descendants who themselves carried the allele) regularly produces homozygosity of a recessive ‘bleeding’ allele, causing ‘bleeding’ in stock even today.  Hermit himself may have inherited his tendency to break blood vessels from alleles derived via two of the 67 crosses of Bartlett’s Childers (also known as ‘Bleeding Childers’) in the first 12 generations of his pedigree. So much for the efficacy of ‘weeding out’ recessive influences by practising line-breeding!  As with closer forms of inbreeding, intensive ‘line-breeding’ is just as likely to bring out recessive negative factors as it is recessive positive ones. Whereas one negative characteristic might be enough to stop an animal becoming a champion, a single positive one will never be sufficient to make it so.  There is no way of avoiding this possibility; so, as a breeder, you should accept that there is more risk than reward if the foals you breed are closely inbred – the closer the inbreeding, the greater the risk.  You may be fortunate; you may get an Enable rather than her unraced sister, Lenient. But don’t fool yourself: the evidence is clear. Close inbreeding is likely to hinder rather than help your breeding endeavours. As the respected authority Harry Callaghan once remarked: “With inbreeding, the question you got to ask yourself is: ‘Do I feel lucky?’” P.S. My lovely wife groans whenever I (mis)quote ‘Dirty Harry’, but fortunately she never gets this far in my articles so she won’t know I have.

[Nerula 1,523]

Thanks will take a bit more reading

[Dopey 253]

Good post

[Pheroz 145]

One of our recent outstanding horses was Imperatriz, no inbreeding at all , only duplication was Northern Dancer 5 X 5.  One good example of his theory.

I have a small share in a filly racing at Te Rapa. this weekend, Sir Tristram 3 X 4., is she one of the lucky ones?

When selecting a yearling should we put a line through all inbred animals?

You might miss the next Galileo though

Excellent food for thought,

thanks for posting

[nomates 5,422]

Funnily enough no one in Usain Bolt's family could run to save themselves .

And I'm talking humans .

[Blaird 493]

An interesting pedigree I came across the other day, Ivy Dazzler, grand dams are half sisters 

[Dopey 253]

3 hours ago, Blaird said:

An interesting pedigree I came across the other day, Ivy Dazzler, grand dams are half sisters 

You might be interested in Schwarz pedigree then … Caulfield today

[Blaird 493]

3 minutes ago, Dopey said:

You might be interested in Schwarz pedigree then … Caulfield today

Very interesting, thanks

[Dopey 253]

8f is your friend 

[Breeder 644]

If you want see a really interesting line bred filly look at Lot 560 in the Inglis Classic sale. It has 5 lines of Eight Carat through either Diamond Lover or Cotehele House.

[Palatable 62]

My less analytical observation over the last 40 years is that close-breeding success swings in and away over time. Northern Dancer's prepotency for good close-breeding witnessed some fine results in the 80s and 90s. He has no real contender today so I can see why the stats aren't stacking up lately. 

Still, only a few Group 1 winners in NZ over the last few years had no cross in their first five lines, whereas the percentage of non-cross-breeds in the population is higher based on what I see in the Karaka catalogues. 

I would argue that we are in a phase where close-breeding perhaps isn't successful, but that in-breeding within five lines still has an edge. 

[diomed 44]

Similarly, I struggle to see arguments made by some (a polite way of saying I think they are rubbish) that more remote ‘line breeding’ is responsible for the ability of numerous top horses even if closer inbreeding may be unhelpful.

 

In the next few weeks I might have a website foalmare.com that will discuss inbreeding, rheoteric light with a supply of data and analysis.

It will look at duplications in pedigrees (I dislike bunfights about the definitions of inbreeding and linebreeding).

In Jan/Feb 2017 I extracted the duplications from 159,200 rated horses and compared the ratings to the duplications (18 different duplication types ... inbreeding is many things).

There is a connection between increases in a few types of duplication and ratings, the higher the count the higher the rating.

 

I hope to explain how great breeders produced their masterpieces, and that it was done by planned pedigrees.
An example of the lack of understanding is the comment in the Bibliography at the back of Breeding For Racing (1976) by John Hislop.
The Italian Federico Tesio bred many great horses including four unbeaten runners, the best Nearco (14 wins) and Ribot (16 wins).

John Hislop's comment on Tesio's book, Breeding The Racehorse
"A short dissertation on breeding racehorses, including some unorthodox and unscientific views.  Any opinion 
of so distinguished a breeder as Tesio is of interest, but this is no guide to producing a Nearco or a Ribot."

In Chapter Seven, Breeding For Speed, Tesio explained what was necessary but did not go into full detail.
People did not investigate what he said.
I have a 29th April 2004 Racing Post newspaper article "Tesio - the Einstein of the breeding world", the 50th anniversary of Tesio's death 
The respected breeding writer/expert Tony Morris says in the full-page article 
"Everybody wanted to know how he did it. Everybody still want to know how he did it"
"Tesio's own book, eagerly devoured by all and sundry, at once fascinating and frustrating. No revelations, no explanations. The enigma remains."

I can explain how Tesio (1869-1954) produced his great horses Nearco (1965) (m) and Ribot (1952) (m).
 

 

Here is the pedigree of Ribot (1962) (m), twice winner of Europe's biggest race, the Prix de l'Arc de Triomphe.

The duplications are of two sires, St Simon (and his sister Angelica once) and Cyllene.

The non-essential horses were removed.

 

St Simon sons: Rabelais; William The Third; Florizel; St Frusquin; Persimmon; Chaucer; Persimmon; Persimmon

St Simon daughters: Simona; Cheery; Roquebrune; [ANGELICA full sibling]; Simonath

That is 8 sons and 4 daughters of St Simon, and his full sister Angelica is also present.

 

Cyllene's sons: Cicero; Cylgad; Polymelus; Polymelus

Cyllene's daughters: Seraphine; Cyclamen; Maid Of the Mint;

That is 4 sons and 3 daughters of Cyllene.

 

Support means a parent or grandparent of the duplicated ancestor elsewhere e.g. Galopin (St Simon's sire)

Support adds to the inbreeding group.

 

Only 19 instances of those two ancestors in Ribot's pedigree, 12 producing sons, 7 producing daughters

 

 

 

Tesio's other good one, Nearco, has as everyone knows, two sons and two daughters of St Simon.

Nearco also has the 7/8 siblings Quiver (f) and Musket (m)

Nearco has a daughter and son of Isonomy (m)

Nearco has two sons and one daughter of Hermit (m)

Nearco has three support lines to St Simon (his sire Galopin three times)

Nearco has in his 6th generation 5 sons (St Albans; Blinkhoolie by full sibling Rataplan; Doncaster; Knowlsley; Lord Lyon; )

and 5 daughters (Sandal; Thrift; Aline; Celerrima; The Princess Of Wales) of Stockwell (m) "the emperor of stallions" 

* "son of full sister" in the chart should read "son of full sibling"

 

 

If you want another example of remote duplications in a very good horse look at Galileo (1998) (m) who has 58 duplication groups in 10 generations.

The number of duplication groups is of no importance.

An amazing 56 of those 58 duplication groups (the majority duplicated sires) have female offspring.

You have to go back to the 25th group to find the first group of all sons of a duplicated sire.

 

You might not realise that is unusual but Northern Dancer in my data appears 103,503 times in the three generations (i.e. his great grand-children).

Northern Dancer produced 522, they produced 19,680, and they produced 103,503.

The 201 stallion sons of Northern Dancer were very busy as people cashed in on the super sire.

The 103,503 in three generations were 96,886 through ND sons and 6,610 through ND daughters. (a ratio of 14.66 sons to 1.00 daughters).

What do you get in 21st century pedigrees?  An excess of sons of Northern Dancer; Mr Prospector (267 stallion sons).

Let's bang the drum for bigger stallion books and more shuttling. 

 

Have I made a case for the defence?