| 2015-05-01 |    |
Scientists Identify Cause of Growth Disorder in Cattle
Young cattle that barely grow or gain weight despite normal feed intake, while relatively rare, scientists have identified the cause of this growth disorder using Fleckvieh Cattle.
Thanks to comprehensive DNA analysis, researchers have succeeded in predicting the occurrence of this disease and determining the precise genetic cause – knowledge that could now help to prevent its propagation in cattle breeding.
The Fleckvieh is one of the four most important rearing cattle breeds, currently accounting for an estimated 40 million animals worldwide. With artificial insemination now being the main mode of cattle breeding, a single breeding bull can generate over a hundred thousand progeny
The genomes of most of the Fleckvieh cattle can thus be traced back to a small number of ancestors. Individual animals within current populations are closely related, allowing recessive traits and disorders to spread unnoticed. These only become evident when the relevant predisposition is passed on by both parents, making the offspring homozygous for that particular trait.
Genetic mutation stunts growth
A research team drawn from Technische Universität München (TUM), Austrian data processing service ZuchtData and the University of Veterinary Medicine, Vienna, has now identified a recessively inherited disease in the Fleckvieh cattle breed that was previously unknown.
“The affected calves and young animals exhibit significantly stunted development in comparison with their healthy contemporaries despite normal feed intake – growing at roughly half the pace and gaining only half the weight. Apart from that, though, they look completely healthy,” explains Dr. Hubert Pausch from TUM’s Chair of Animal Breeding.
Researchers examined bovine genotypes for specific genetic features that can indicate diseases. They discovered four regions of the genome that have a negative impact on reproductive and rearing success – and animals homozygous for one of them were significantly stunted in growth. With the aid of comprehensive genome sequencing analysis, the researchers were then able to identify the genetic mutation responsible for this growth disorder.
Similar condition in humans
In all the growth-stunted animals examined, the SLC2A2 gene was affected by a mutation. The result of this is that a specific glucose transporter in the body either does not function correctly or is not formed in the first place. In humans, this rare metabolic disorder is known as Fanconi-Bickel syndrome.
Although the mutation responsible for stunted growth in Fleckvieh
cattle has only now been discovered thanks to sequencing, it appears
that individual cases of this disorder must have occurred over
at least the past two decades.
Using a historical paraffin-embedded sample, the scientists also
prepared and analyzed the DNA of a young bull that exhibited the
relevant symptoms in 1996. This animal was also found to carry
the newly identified genetic mutation.
Systematic genetic analysis to improve animal health
Such DNA analysis and the resulting ability to determine which genes and genetic mutations are responsible for specific traits or disorders could simplify and improve cattle breeding significantly. Breeding bulls have already been routinely genotyped for several years now.
“By extending this to female animals, problematic matings could be avoided in the future – particularly since certain widely used bulls are genetic disease carriers,” explains Pausch. This would enable faster achievement of desired breeding results and prevent many genetic disorders.
Genome sequencing of Fleckvieh bulls has been coordinated by TUM as part of the Synbreed network of excellence since 2009.
