Genetic Conditions

GENETIC CONDITIONS IN WAGYU CATTLE

All breeds of cattle, in fact all mammals including humans, have undesirable genetic conditions. Fortunately, advances in molecular genetics have facilitated the development of DNA tests for their management. Breed Societies are at the forefront of development of strategies to manage undesirable genetic conditions and seedstock members are leading the industry with their uptake of this technology.

The known genetic conditions of Wagyu are as follows.

Spherocystosis (B3) – This is a disorder of the surface membrane of the erythrocyte (red blood cells). The protein from the B3 gene makes up the basic structure of the erythrocyte. Cattle that are homozygous (have two copies of the recessive allele) have pernicious anaemia (bleeding caused by the abnormal red blood cells). Death normally occurs within the first 7 days after birth. Some cases live to adulthood but there is a severe retardation in growth.

Chediak Higashi Syndrome (CHS) – CHS is a macrophage disorder (a white blood cell that has an important role in the immune response to disease). If cattle have a malfunctioning immune system, this makes them unable to resist bacterial challenge. Blood is slow to coagulate so often the first indicator is unusual umbilical cord haemorrhage at parturition (calving). Cattle with this syndrome often have an unusually pale coat colour.

Claudin 16 Deficiency (CL16) – CL16 (also known as RTD or Renal tubular dysplasia) is a gene disorder on chromosome 1 and causes kidney failure (chronic interstitial nephritis often with zonal fibrosis or excess of fibrous connective tissue). This disorder results in terminal kidney failure and the onset can occur any time from late adolescence. Cattle are unlikely to live more than 6 years.

Factor XI deficiency (F11) – F11 is a plasma protein that participates in the formation of blood clots. Factor XI deficiency is an autosomal disorder that is associated with mild bleeding in Wagyu. Affected animals show prolonged bleeding time and abnormal plasma coagulation after trauma or surgical procedures such as castration or dehorning. It is also possible that Carrier x Carrier matings have increased difficulty producing viable fertilized embryos or full‐term pregnancies and are may be repeat (return to cycle)breeders. Note – this is generally a non-lethal recessive condition with affected animals being able to live and breed as normal.

Note – There are other recessive genetic conditions known to exist in Wagyu cattle (e.g. F13) however they have not been identified in the Australia Wagyu population.

How are the conditions inherited?

Research from Japan indicates that B3, CHS, CL16 and F11 are simply inherited recessive conditions. This means that a single pair of genes controls each condition. For this mode of inheritance two copies of the undesirable gene need to be present before the condition is seen; in which case you may get a calf with the symptoms of B3, CHS, CL16 and F11.

Animals with only one copy of the undesirable gene (and one copy of the normal form of the gene), that appear normal (i.e. no symptoms), are known as “carriers”.

What happens when carriers are mated to other animals?

A carrier will, on average, pass the undesirable gene form to a random half (50 %) of their progeny.

When a carrier bull and carrier cow are mated:

•   There is a 25% chance that the progeny produced will have two normal genes and so will never pass on the undesirable gene.

•   There is a 50% chance that the mating will produce a carrier.

•   There is a 25% chance that the progeny will inherit two copies of the undesirable gene and hence be affected by the genetic condition.

When a carrier animal is mated to an animal tested free of the genetic condition:

•   All progeny will appear normal and will be unaffected by the condition.

•   There is a 50% chance that the mating will produce a carrier.

•   There is a 50% chance that the progeny produced will have two normal genes and so will never pass on the undesirable gene.

Note that an animal that is tested free by DNA test of the genetic condition will not pass the genetic condition to its descendants, even if it has carriers in its own ancestry. Therefore, DNA-tested free animals can be used in your breeding program with confidence that they are not transmitting the unfavourable gene to subsequent generations. 


USING GENEPROB FOR GENETIC CONDITIONS

The GeneProb analysis interrogates the pedigree of each animal and calculates the probability that the animal is a carrier for each genetic condition from the known DNA information of their relatives. For example, if an animal’s dam had been tested free of the genetic condition but the sire was a tested carrier, the animal would be reported as having a 50% chance of being a carrier.

The gene probability analysis includes all known DNA information for animals recorded on the Australian Wagyu Association (AWA) database. Genetic test results are based on samples provided by breeders.

Disclaimer: The Australian Wagyu Association makes no statements, representations or warranties about the accuracy or completeness of any information relating to the status of a particular animal: and disclaims all responsibility for information and all liability (including without limitation, liability in negligence) for all expenses, losses, damages, and costs you may incur as a result of information being inaccurate or incomplete in any way for any reason.

Code Explanation

(The first two, three or four characters vary with the genetic condition – ie. B3, CHS, CL16 or F11)

_ _F Indicates that the sample submitted for this animal has been tested and found to be free of the causative mutation responsible for the indicated genetic condition. This animal is homozygous free, meaning that it has two copies of the normal variant (or allele) of the gene.
_ _C Indicates that the sample submitted for this animal has been tested and found to be a carrier of the causative mutation responsible for the indicated genetic condition. This animal is heterozygous for the mutation, meaning that it has one mutant allele and one normal allele. This animal could pass the mutation to approximately half of its progeny.
_ _ __% Indicates that, based on pedigree information supplied by the breeder of the animal, the animal has a chance to be a carrier of the mutation responsible for the indicated genetic condition but has not been tested. The higher the indicated percentage, the larger the chance the animal may be a carrier
_ _FU Indicates that, based on pedigree information supplied by the breeder of the animal, the animal is expected to be free of the mutation responsible for the indicated genetic condition. However, this animal has not been tested for the causative mutation and the AWA gives no guarantee as to the animal’s “free” status.
_ _A Indicates that the sample submitted for this animal has been tested and found to be affected by the genetic condition. This animal is homozygous for the mutation responsible for the genetic condition and has two copies of the mutant variant of the gene.

It is important to note that the GeneProb results are only current at the date of publishing and are limited by the DNA test result and pedigree information available. The results may change as further DNA testing is performed, particularly when the level of testing that has been conducted is relatively low. The AWA Animal Search facility will consequently become the best source of data on an animal’s status, with the GeneProb results being routinely updated in the future.

Testing For Genetic Conditions

Animals may be tested for Genetic Conditions using DNA test services. These tests may be requested using the Recessive Gene Test Authorised Test Form.

Our preferred DNA lab in Australia is the University of Queensland Animal Genetics Laboratory (UQAGL). If the animal has already been DNA parent verified at UQAGL using a hair sample then some of the remaining hair sample may be used for this test. However, if no preceding DNA tests have been conducted then a hair sample must be sent with the form in the standard hair collection kit which may be obtained from the Association – email the Registrar on office@wagyu.org.au or call (02) 6773 3342.

UQAGL extracts the DNA and sends it to the Elizabeth MacArthur Animal Institute (EMAI) which conducts the recessive genetic testing and returns the results to the member, copy to the Association which then invoices the member. UQAGL is also developing SNP based genetic condition tests which will be available in 2015. Additional advice is needed on the specific process for sending DNA samples to UQAGL from overseas.

How should genetic conditions be managed?

An informative presentation on the management of genetic conditions was delivered as part of the “Know Your Genes” webinar course conducted by Southern Beef Technology Services (SBTS).

This presentation can be viewed from the following SBTS website: http://sbts.une.edu.au/Webinars/webinars.html