Many questions and misconceptions have arisen around the topic of "genetic disorders". Especially due to the fact that the aspect of being "free of genetic disorders" is seen as an absolute and determining quality criterion.
The quality is more significantly determined by the pedigree, frame, milk yield, inheritance of marbling, etc.!
The consideration of the inbreeding coefficient in the small initial population also plays a significant role in the health of the animals. After all these criteria, matings should be planned taking into account the possible presence of genetic disorders. Thus, a genetic defect does not exclude any animal in use as a breeding animal.
Even some of the most famous sires from Japan are carriers of genetic defects:
- Itomoritaka J2703: CHS
- TF 147 Itoshigefuji: CHS
- TF 148 Itoshigenami: F11
- Fukutsuru J068: F11
- World K's Yasufuku Jr: CL16
- Kitateruyasudoi J2810: F11
This list is not exhaustive, but only exemplary. If these animals would not have been exported due to the genetic disorders or if they would have been taken out of breeding immediately after the knowledge of the genetic disorder, the purebred Wagyu breeding would probably hardly exist today. So every very good breeding animal is still needed and for the bulls of the first hour top prices are paid for the semen.
Known genetic disorders
The six genetic disorders known to date are autosomal recessive genetic disorders. This means that the genetic disorders only occur if they are present on both alleles.
- CHS (Chediak Higashi Syndrome):
This is a disorder of macrophages (white blood cells that are important for immune defense). As a result, animals with CHS have a lowered immune response and more frequent bacterial infections. Signs include slower blood clotting and a noticeably pale coat color. An initial indicator is unusual bleeding around the umbilical cord at birth.
- B3 (Spherocystosis):
This is a disorder of the surface membrane of erythrocytes (red blood cells). The protein from the B3 gene forms the basic structure of the erythrocytes. Cattle that are homozygously affected (i.e. have two copies of the recessive allele) suffer from anemia due to the abnormal red blood cells. This usually leads to death in calves in the first 7 days. There are also cases that have lived longer but were then severely stunted in growth, for example.
- CL16 (Claudin 16 Deficiency):
This is also known as RTD or renal tubular dysplasia. The accumulation of fibrous tissue leads to a greatly increased risk of renal failure. The condition can occur at any time during growth and then results in animals usually not living beyond 6 years of age.
- F11 (Factor XI Deficiency):
Factor XI deficiency is an autosomal disorder associated with a slightly increased bleeding tendency in Wagyu. Coagulation factor XI is reduced in efficiency. Affected animals show slightly prolonged bleeding times and unusual plasma coagulation after trauma or surgery. This inherited disorder is not lethal and has no effect on the animal's life, which is usually quite normal.
- F13 (Factor XIII deficiency):
This genetic defect is very rare and therefore not very common. If animals are affected, there is a severe deficiency of the fibrin-stabilizing factor 13. Bruising and bleeding are typical symptoms, often occurring on the hindquarters of affected calves. The slightest injury can be a trigger.
This hereditary disease, first announced in September 2020 by the Australian Breeders' Association, refers to "weak calf syndrome." This manifests itself in longer gestation periods, but where the calves are still weaker/lighter. Often they do not suckle well after birth, so they then die after a few days. The number of abortions from pregnancies is also higher.
Categories of genetic disorder diagnostics
F (free): These animals are free from the tested genetic disorder. Sometimes in the pedigree overviews of the Australians and Americans the letters FU are used - this is used when both parents are proven not to have the genetic disorder and therefore it can be deduced that this disorder does not occur in the offspring.
C (carrier): These animals carry the genetic defect on a mutant allele and are phenotypically indistinguishable from a healthy animal.
A (affected): These animals are affected with the respective genetic disorder. Both gene loci are mutated and the gene defect also appears phenotypically.
A prerequisite for correct breeding is that the animals are examined for genetic disorders!
A prerequisite for proper breeding is that the animals are tested for genetic disorders. Animals that are only "carriers" have to be used for breeding if they are suitable for breeding. It is important to avoid that "carriers" are mated with the same genetic defect.
Please refer to the following scheme for breeding management to find out what has to be taken care of:
|Mating||Distribution of offspring|
|Free x Free||100%|
|Free x Carrier||50%||50%|
|Carrier x Carrier||25%||50%||25%|
|Free x Affected||100%|
|Carrier x Affected||50%||50%|
|Affected x Affected||100%|
Important! The impact of the genetic disorders will only have an influence when animals have the status "affected"
For every breeder it is important that the animals are tested for potential genetic disorders. This is the personal responsibility from the breeder towards his animals!
Being free of genetic disorders can offer an additional benefit as a sales argument for the buyer. But this should not be overestimated. As already mentioned, factors such as pedigree, proven inheritance of desired traits such as marbling, creaminess and milk yield are much more important. So what is the use of animals that are free of genetic disorders, but are no longer suitable for breeding?
The presence of a genetic defect has no effect on the herdbook.
Therefore, we should be pleased to have a broad breeding population consisting of animals without genetic disorders or so-called carriers - these are a valuable contribution to the further development of Wagyu breeding in Germany and Europe.