Progressive Ataxia (PA) in Charolais Cattle
The PA (Progressive Ataxia) gene has been in Charolais cattle for over five decades. However, it has only come to light in recent times.
The French Charolais Society has been monitoring the gene for many years and aims to eliminate the disease within its herdbook.
According to UC Davis Veterinary Medicine, it is an inherited neurodegenerative disease that impacts an animal’s hind limbs that can gradually progress until it cannot stand.
One breed society described the visual sign of PA as “an animal that begins to walk as if it is drunk”.
Generally, the onset of the disease occurs around 18 months of age; however, it can be as early as 6 months or as late as 3-5 years of age.
According to its veterinary genetics’ laboratory, breeders with Charolais, Charolais-cross and Blonde cattle test for the gene.
Animals can carry zero, one or two copies of the gene. It states that two copies of the defective gene are required for the presentation of the gene.
Recent estimates suggest the frequency of PA mutation in the Charolais breed to be approximately 13%.
The University of California explained that cattle can fall into three different categories:
- N/N genotype: Will have this progressive ataxia and cannot transmit this progressive ataxia variant to their offspring;
- N/PA genotype: Will not be affected by this progressive ataxia, but are carriers. They will transmit this progressive ataxia variant to 50% of their offspring. Matings between two carriers result in a 25% chance of producing a calf with this PA;
- PA/PA genotype: Will have this progressive ataxia, a neurodegenerative disease, and will transmit this PA variant to all offspring.
Single and double carriers
In light of this, the British Charolais Cattle Society has issued guidance to its breeders and made some amendments to its bylaws to enable them to make “informed” breeding programme decisions.
In documents circulated to breeders, a spokesperson for the society said:
“There is no reason as to why breeders should shy away for a single carrier of PA providing, they know the status of the bull/cow they are mating them with”.
As per its guidance, animals who carry one copy are normal but can potentially produce impacted offspring if you breed to another. Meanwhile, the disease impacts double carriers and “you must avoid these”, says the society.
It added that double PA carriers could have a “disastrous” impact on the herd and, therefore, says farmers must eliminate them from the breed.
It highlighted that the disease does not impact single carriers but they can potentially produce affected animals if you mate them with another carrier.
For instance, it advises that you must not mate single carriers with other single carriers.
Importing semen and animals
In a statement, a spokesperson for the British Charolais Cattle Society said:
“If you import any new animals or semen from outside of the UK, then the animals must have been tested free of progressive ataxia to be accepted into the herd book.”
“If you are placing bulls on the semen royalty scheme, they will only be accepted if the bulls are tested free of progressive ataxia.”
“Bulls that have entered AI centres in France will already have been tested for Progressive Ataxia.”
“The society would like to encourage members to test their stock bulls/ females and any new potential stock bulls or females coming into their breeding programme. Once you know the status, you can make informed decisions on mating,” they added.
Testing for PA
It is not currently possible to test for PA from a genotype at present; however, you can do so by taking a hair sample and sending it to a laboratory.
If animals have an existing DNA test, the society can instruct the lab to conduct tests from the original sample.