Why do a pedigree control?

A type inspection board had previously been set up, which traveled the country to try to determine whether the horse was a purebred cold-blooded stallion or not. As this was an almost impossible task, after a while blood typing was used, which could then quickly curb the illegal breeding.

In 1969, compulsory pedigree testing was introduced for all cold-blooded trotters prior to registration with the STC. Soon, other breed associations followed suit and introduced pedigree testing of, for example, warmblood trotters, racehorses and Arabian horses. In the early 2000s, blood typing was replaced by the more modern DNA typing, which has greater potential for large-scale operations, and is also better at detecting incorrect pedigree. Today, many breed societies, both in Sweden and around the world, have introduced mandatory pedigree checks before registering horses in their studbooks.

Of course, it depends on what you want to achieve with your breeding.

In order to make rapid breeding progress, great care is needed in the selection of breeding individuals. An important tool, which is currently used with great success, is the BLUP index, which gives an indication of which individuals are suitable for breeding. The BLUP index is based on the individual's own results as well as the results of the ancestors, which is why it is very important that the horse has the right pedigree. For example, a breeding stallion can take into account the performance of his offspring. A very successful offspring may then give a higher BLUP index and if this offspring actually has another sire, the BLUP index will of course be completely misleading. In addition, other mare owners may choose this stallion because he has produced good offspring. That's not a good idea either, because then you're choosing the wrong stallion and risk not making any breeding progress. It is important to choose the right individuals in the breeding work to get the best possible offspring.

The National Board of Forensic Medicine has calculated that about two percent of all children born are subject to a paternity investigation. About the same proportion of foals born do not have a proper pedigree either. There has been some increase in the proportion of cases in recent years and it is now estimated to be around 3-5% with some variation between breeds. The increase in cases with incorrect pedigrees is due to several factors, one of which is that DNA typing itself detects more cases that previously could not be detected by blood typing.

A major contributor to the increase may be the now widespread use of semen. Human error cannot be ruled out in bottling, labeling of doses, shipping and unpacking. Other causes may be the change of stallion during the breeding season, as well as the use of stallions for poaching. A further cause may be that two foals are confused at some stage.

It is important to remember that the strength of a pedigree check lies in the exclusion of kinship, the efficiency is then 100 percent. Proving a relationship, on the other hand, is much more difficult but with the DNA methods used today, the control is still very reliable. The exclusion capacity when both parents are DNA typed is over 99% but drops to about 95% if only one parent is DNA typed.

If, for example, the stallions in a paternity case are also closely related to each other, the efficiency drops slightly further. This is one reason why it is often necessary to DNA type the mare as well, no matter how sure you are that she is the mother of the foal. Exclusion capacity also varies slightly between breeds and is naturally higher in the breeds that are least inbred, i.e. where there are many individuals that are not closely related to each other.

A common misconception is that completely unknown parents can be found using DNA typing. This is practically impossible as it would require a worldwide database of all DNA-typed horses, require enormous computer resources and also risk that several horses by chance would happen to fit as parents. Therefore, to properly solve a case of unknown pedigree, the horse owner must first find out as much as possible about the origin of the horse in order to suggest a reasonable number of possible parents and ensure that samples are available from all of them. From this starting point, the incorrect parents can then be eliminated, leaving only one pair as possible parents.

Another common question is whether it is possible to see any other characteristics of the horse or to see which breed it belongs to. Again, these are not questions that can be answered by DNA typing as they are completely neutral markers used in pedigree testing.

The first thing to do is to find out what the rules are in the breed society where the horse is to be registered. Some breed societies, as mentioned earlier, have mandatory pedigree checks on both the sire and dam in order to register the horse. Other associations only require checks against the sire. Other rules may also apply to older horses not yet registered as well as imports etc.

Once you know what level of pedigree check is required, it is useful to find out if the parents have been DNA typed before. If the sire is an approved stallion, he is most likely already DNA-typed, but other stallions and mares may need to be DNA-typed at the same time as the offspring. You can find out what has been done on the parents at the same time as you order sampling material from the Animal Genetics Laboratory, SLU.

The order can be made by phone, 018-67 28 04 (Mon-Fri 10-11), via our Order form or email hgenlab@slu.se.

In order to perform DNA typing, a sample of about 30 hairs, pulled out by the hair roots, is needed from the tail. Blood or other tissue can also be used for DNA typing, but routine activities are set up for hair samples, so other samples may take longer to analyze. A clearly completed referral form is sent with the sample, giving details of the horse and its owner. If someone other than the owner is to receive the results, this should also be filled in.

The results of the DNA typing are then sent together with the registration application to the registering association. The results also follow the so-called ISAG nomenclature and are therefore also internationally valid.