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By Johan Dreyer

A Breeder’s Notebook Selection is the mainstay of breeding

In breeding horses there is no substitute for quality – you have to strive for excellence. Unlike the time when a horse was primarily a means of transport, horses today in every endeavour compete on an individual basis, therefore aiming for a good average is not enough. It follows that to succeed in breeding horses today you have to plan to breed a horse better than that which is now the best. Exorbitant as it may sound, it is the only way to go if you have success in mind. In theory this is even more unpredictable than breeding for a good average and the only way to achieve this is by breeding to strong points. In the context of the unpredictability of breeding in general (as breeding guarantees nothing and there is always an exception), the importance of striving for excellence should be obvious. We breed horses for some kind of activity yet select for conformation, although function does not by necessity follow form. This will be exaggerated once the horse starts performing, as his conformation by comparison becomes                               

have to visualise your goal not in terms of conformation per se, but in terms of what that conformation means for the performance you want. This is very important and the only logical starting point. Only when you have visualised your goal – the desired performance – can you select the conformation necessary to get there. (That implies that                                

in hand you can select according to strong points – this is the only viable route to breeding that individual that will perform far above average. Correcting weaknesses in an individual should be no more than an added advantage and                             

you want, do not develop tunnel vision. Keep an open eye and analyse what you see because there is an old adage in racing: “They run in all shapes and sizesâ€?. You simply cannot afford to stop analysing, thinking, learning and adapting. Although obvious, it is pertinent to state that manipulation of the gene pool cannot improve the quality available. Different breeding patterns can at best only serve to increase the frequency in appearance of the available quality. The quality of the gene pool available is a determining factor in the success of a breeding enterprise. Rating the gene pool in selecting breeding stock is thus of paramount importance. Unfortunately it’s not written in black and white and interpreting indications is the best we can do: - Although the appearance of a horse (phenotype) has little value in determining the genetic value of an animal, excellence in the individuals concerned is still the best preliminary indication of inheritance of a superior gene pool. - Secondly, although a horse’s pedigree is but a limited indication of his genetic possibilities (and a small part of what he eventually turns out to be), good dams and good sires, that is, dams and sires with a proven track record of hereditary                               ancestors but it is only if you are familiar with them.                               


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the superiority of the gene pool coincides with the strong points you are trying to breed to and without bringing in its wake debilitating weaknesses. The superiority or not of a gene pool can only be          "   

of genes for something not coinciding with your              

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genes becomes, the stronger selection will be and eventually the better the chances of success. The British successfully developed the thoroughbred and the Americans developed the standardbred, both in relatively short periods of time, as the world’s premier racing and trotting breeds. They both eclipsed much older breeds of horses by a single-minded selection to speed, in other words strongpoint to strongpoint.

the breeder uses, his ultimate success depends on the quality of the gene pool with which he works and not how he manipulates it� . In other words, %         #  &

not that big. Establishing a superior gene pool $&          

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Successful breeding unfortunately is not that simple          

outcome of a mating, for instance prepotency. It’s no use in breeding if a horse has a superior gene pool yet fails to perpetuate that in his offspring. Prepotency is the ability of an ancestor to stamp desirable characteristics upon their offspring. Not only are there huge differences in prepotency for different characteristics within one individual, there are similar variants for the same characteristic in prepotency between individuals also. As we all Every new individual when conceived is endowed know, breeding involves two individuals, both with a random selection of genes. Selective with a set of different genes each with its own    $     prepotency for different characteristics in each          #   # individual. That leaves us with compatibility jiggling the blocks.The reason being that if more of between individuals as the determining factor the same genes are offered for the “random pickâ€?, rather than the prepotency in any one or both the probability of appearance of the mentioned of them. Determining prepotency and therefore genes must be greater, “the presence of close compatibility of a sire are not that complicated inbreeding in a close ancestor of the key horse has an issue because of the quantity of his offspring, occurred too often to be ignored as a favourable which provides us with enough evidence. In a feature in the make-up of both sires and damsâ€? dam, because of the lack of quantity, determining . This tends to hold true but extensive research prepotency and therefore also compatibility can on thoroughbreds shows that intensive inbreeding be rather precarious. Breeders have claimed for results on average in a decline in physical vigour, centuries that prepotency is the result of purity capacity for physical performance and in nervous of blood, “the poor chances at stud of a brilliant stability. Yet genetic diversity supplies the building horse with a moderate pedigree must be the blocks that are essential for genetic improvement. nearest thing to a certainty in breedingâ€? .Yet there Therefore methods have been devised to utilise is ample evidence of remarkable prepotency in the concentration of genes achieved in inbreeding sire lines lacking in purity as well as inbreeding. “I yet defer from intensive inbreeding as well as do not deny that there had been close inbreeding accommodating genetic diversity. Line breeding is a in a pedigree in otherwise inexplicable cases of variation of inbreeding where a common ancestor prepotency, but I can see no practical reason is evident in preferably the third or even the fourth why a stallion should be ignored because he is an generations in both the sire and dam’s pedigree. outcross, nor preferred because he is inbred, or “Give a sire back the best of his damâ€? is the most vice versaâ€? . common pattern practised in line breeding. But from the discussion it should be evident that To complicate matters, there may be characteristics “regardless of the considerations of matings that $         


evident in the individual concerned but lurking in the genes with varying degrees of prepotency. Therefore you have to study pedigree in order to determine compatibility, but that is only useful if you know both the ancestors and their offspring. In studying pedigree always be on the lookout for linkages between characteristics which might be unforeseen and unwanted. An example of this is: if you select for an enlarged forehead in cattle, body mass will decline (enlarged sinus cavities is a tropical characteristic and genetically linked to a decline      Another factor that has to be accounted for in predictions on the outcome of a mating is the dominance and recessiveness of some genes over others. This is linked to prepotency and although the effect of this phenomenon is quite well known for some criteria like colour, it is rather unknown for others. A lot of study has gone into managing this effect but it still plays havoc with predictions on the outcome of a mating. Mostly because dominance can be absolute but is not necessarily so, the same goes for recessiveness. A dominant gene can prevent any recessive gene from being evident in the individual although it might be evident in the individual’s offspring. Knowledge of the dominance or recessiveness of genes is rather scant, especially to the degrees thereof, mostly because we perceive and select characteristics not genes. The characteristics we aim to breed are not under the control of a gene but rather a bundle of genes each with varying degrees of recessiveness or dominance. To indicate the complexity we are dealing with, let us take a simple example such as a black horse: black can be the result of two different scenarios, one a relatively dominant black gene, the other a combination of two recessive genes. Chromosome analysis will reveal which is which, but is not available to most of us, as will

a pedigree study if you know the ancestors and their respective colours; unfortunately you are not always that lucky. A horse’s ability is not the mathematical calculation of all his strong points minus his weaknesses. It is a fact that certain desirable characteristics, such as length of step, are         )  

same characteristic is enhanced or degenerated by other features (a totally different bundle of  #        

own could have been of little consequence. It follows that an outstanding individual is not simply the result of the union of two pairs of superior gene pools, but the union of two pairs of highly compatible and desirable sets of characteristics $          

    

genes that are not necessarily the same in other     *      $+ /

will depend on the combination of genes that afford him his superior performance and how much of his superior genes are either dominant or recessive. A successful singer needs not be endowed with every aspect of what we would call musical giftedness. By the same argument in breeding, we          

for the desired performance, those that would enhance such a performance and those that would cripple the desired performance. Then we have to dissect each characteristic to understand its make-up and the behaviour of these elements in the key horse, his ancestors and his progeny. Armed with this knowledge          #  

studying the individual, then his pedigree and           

the study, we must search for compatibility of the strong points we aim to breed.

Sources: Previous editions of SA Show Horse Abram Hewitt – Great Breeders and their Methods Joe Thomas – The Blood Horse Sir Mordant Miller – SA Race Horse (Johan can be reached at dreyerjohan@yahoo.com)

A Breeder's Notebook: Selection. Endurance Horse July 2010  

A Breeder's Notebook is a regular featured article in the Endurance Horse Magazine. In this article Johan dreyer discusses tthat selection i...

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