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The Society has been made aware of a small number of pedigree Belted Galloway calves which have been still births or early neonatal deaths as a result of a very rare lethal inherited disorder known as Alpha Mannosidosis (AM). AM is a recessive genetic disorder found in several cattle breeds. There are two known variants, the Angus variant (or AM – 961) and the Galloway variant (AM – 662). A successful screening programme in the 1980s in Australia was implemented which led to its control, and now any imported semen and embryos are genetically screened to prevent its re introduction.
AM is an enzyme deficiency resulting in an inability to properly break down certain sugars in the body’s cells. Accumulation of these sugars can affect many of the body’s organs and systems including the central nervous system. It is known to cause:
- Very early neonatal deaths
Calves affected with the AM gene may have gross deformities including:
- Arthrogryposis (shortened limbs with fixed contracted joints)
- Cleft Palate
- Enlarged Liver and Kidneys
As it is a recessive genetic disorder, it is inherited in a predictable way, in the same manner as other recessive traits, like the red coloured gene in red Belties:
- An affected calf must inherit the mutation from both parents (both must be carriers)
- Two carriers have a 25% chance of having an affected calf, a 50% chance of having a calf who is a carrier and a 25% chance of having a calf which is clear.
- A carrier bred to a clear animal will not have any affected calves, but will pass the gene on to 50% of calves, meaning 50% will be carriers and 50% clear.
A genetic test is available through Weatherbys for AM – 662 which can identify whether an animal is clear, a carrier or in the case of a dead calf, was affected.
The Belted Galloway Council have decided, with immediate effect , to commence a control programme to reduce the prevalence of the mutation which causes this disorder.
As all young bulls being registered have DNA taken, going forward it will be straight forward to test them for AM – 662 as We athe rby’s are doing the usual parentage check. This testing will be done on all bulls now inspected. The small extra testing charge will be covered by the society. Bulls found to be carriers will not be eligible for registration. Weatherby’s estimate these tests will take 4 – 6 weeks.
We are also plann ing to screen all AI bulls, to ensure that each bull can be identified as either clear, or a carrier in our 2023 yearbook. Those approved for use in Australia should already have been tested clear. After a year of testing new and AI bulls, we will have a better idea of how common this disorder is within Belted Galloways and we can refine our strategy, and consider the next steps.
In addition we would encourage breeders to screen their own stock bulls. The re may be enough material already stored for the test. Please contact Christina to consider steps going forward. Members may also choose to test their females, to be sure of their status.
To be clear, this is a rare disorder and Council’s actions may uncover only a very low incidence, but left unchecked, a recessive genetic condition can spiral upwards, especially with the concentration of genes from the use of AI bulls. If we do not reduce the prevalence of this mutation, it would have ser ious consequences for the breed.
Alpha Mannosidosis Update 19th January 2023
Since council have been made aware of the issue of Alpha Mannosidosis (AM) back in October last year, we have made progress on both parts of our strategy to manage the mutation within our breed.
1. Measure & monitor current levels
Up to 19th January we have test results back for 200 animals. This is made up of
- Newly inspected bulls
- AI bulls
- Animals which breeders have put up for testing (both females and stock bulls)
Of these, 43 (21%) have been shown to be carriers. This is a high value, but it’s important to highlight that the majority of the 200 animals tested are from herds which have had breeding problems and think they may have a problem, therefore we expect the real proportion of affected anima ls across the breed to be much lower than this.
We will continue to update you as more animals are tested throughout the year.
2. Select against carriers to reduce the prevalence of the mutation
As livestock breeders we know it is important to choose our breeding animals carefully to improve the quality of our stock. Primarily we do this by choosing a great bull. AM status is one additional piece of information you can use to select your breeding stock. As a council we are carrying out two specific things to help with this:
- All newly inspected bulls must now have a clear AM test to be eligible for registration (from 1st Nov 2022).
– Bulls registered before this will not have registration papers removed if they are found to be AM carriers and can continue to be used. Their calves will have a 50% chance of also being carriers.
– Many breeders have decided they will test potential bull calves to ensure bulls are not raised for inspection unless they have already tested clear.
- All AI bulls advertised by the society in the yearbook and on the website semen list must state the results of an AM DNA test (clear or carrier). Tests are being carried out in advance of this year’s yearbook and so far, results have been very reassuring.
Some breeders are choosing to also test their breeding females and stock bulls. We encourage this but want to highlight again that any males registered before 1 st Nov 2022 or any females found to be carriers will remain full pedigree animals and can be used for breeding. This means unregistered young heifers tested and found to be carriers can still go on and be fully registered. We hope that the additional information will help breeders reduce the chance of breeding carrier to carrier which is the only way to produce an affected calf (There is a 25% chance these calves are affected).
Calculations from Dr Bunning show that even if 21% of the breed are carriers and we carried out no selection against breeding these animals, we’d only expect 1.1% of calves to be affected by AM. This value would vary from herd to herd, so we are still highly encouraging breeders to test their animals and use the information in breeding decisions, but we don’t need to panic! We are confident that our current strategy will manage and reduce the condition without losing the genetic diversity of the breed.