Generalised Glycogenosis (GSD-II), more commonly known as Pompes, is a lethal inherited genetic disorder which has been diagnosed in Brahman and Shorthorn cattle, and the derivatives thereof. The disease is inherited as recessive, in other words, only calves that inherit a mutant gene from both parents will be affected by the disease. The disease occurs because affected calves lack enzyme activity of the essential enzyme acidic-a-glucosidase (AAG). As a result of this, glycogen builds up inside the muscle and nerve cells, and interferes with normal tissue function (Trecenti et al., 2018).
According to Reichmann et al., (1994), calves presented with progressive muscular weakness, with signs becoming most obvious when the animal is stressed, such as during weaning, after weaning the severity of the clinical disease increases rapidly. Affected animals have sunken eyes, adopt a wide-based stance and have a concave arch of the neck reflecting muscular weakness. In some cases, calves/weaners experience difficulty rising and may be found lying on their side paddling in an attempt to rise. (Australian Brahman Breeders Association Ltd.). Death usually occurs between 6 and 9 months of age. However, with careful nursing of affected calves, they may survive up to 12-13 months of age. In some cases, glycogen accumulation in the heart can cause a sudden heart attack. Only a small portion of actual cases, as most calves appear to have died of misadventure. This is a consequence of the non-specific nature of the clinical signs shown by cases, the extensive grazing conditions this breed is subject to and the random nature of presentation of sick, single animals.
Pompes is inherited in a simple recessive manner which implies that animals that are homozygous normal (NN), are free of the mutation. Animals that are heterozygous carriers (Nn), will have one copy of the Pompes mutation on the recessive allele. Heterozygous carriers of Pompes do not express the symptoms of Pompes, they are only expressed in the affected (nn) animals, who have two copies of the mutation on the recessive alleles (homozygous recessive). Pompes can be managed to keep allele frequencies of the mutant gene low, in order to do this, however, the disease status of the animal needs to be known. If you mate two normal (non-carrier) parents, all the progeny will be free of the disease. If you mate one normal parent (NN) with a carrier parent (Nn) the outcome of the mating will on average present 50% normal progeny and 50% carrier progeny. If you mate two carrier parents (Nn) with each other, will produce, on average 25% normal progeny (NN), 50% carrier progeny (Nn) and 25% affected progeny (nn).
