A discovery by CSIRO scientists is central to the Australian Poll Gene Marker test, which is helping Australian cattle breeders select the best breeding cattle. It may also help the industry end the painful practice of dehorning beef cattle.
Dehorning cattle is costly
Most cattle, especially in Northern Australia, have horns. Hornless cattle are safer to manage due to reduced risk of injury from horns, between animals and the people handling them. Also, in Australia, beef cattle are often transported for long distances, which adds to the risk of injury from horns.
To reduce these risks, dehorning became a common husbandry practice in modern farm management. However, dehorning is a labour-intensive procedure, costly and has implications for animal welfare. An alternative management practice was sought to overcome the need or reduce the practice of dehorning. Breeding hornless cattle is one alternative solutions.
Selective breeding of naturally hornless (polled) cattle also comes with its challenges. The way horns (or the lack of) are inherited from parents to offspring cannot be determined visually because two hornless cattle can have horned calves. A DNA-based test was required to reduce horns in any herd.
DNA-based test for hornless cattle
The way in which cattle inherit horns or no horns means that a DNA-test is needed in order to breed naturally hornless beef cattle.
Back in 2010 the first generation of a DNA-based Polled Gene marker test became available to the industry. It was based on technology called microsatellites. The DNA marker proved successful in research trials conducted across Australia by the Co-operative Research Centre for Beef Genetic Technologies (Beef CRC), CSIRO, and Meat & Livestock Australia (MLA), in collaboration with the Animal Genetics and Breeding Unit (a joint unit of Industry & Investment New South Wales and the University of New England).
In 2013, an updated test was released that used a newer technology based on single-nucleotide-polymorphism (or SNP). This new test was more accurate and easier to integrate into laboratory testing routines, becoming available through several providers worldwide.
Unfortunately, both tests underperform when applied to tropical cattle (Bos indicus) like Brahman and its crosses. Nowadays, at least four DNA mutations lead to the hornless phenotype, but not all are present in any given breed of cattle. The situation within European (Bos taurus) cattle is much clearer when compared to Bos indicus cattle.
In response, CSIRO researchers identified an effective DNA-based test for polledness in these genetically complex Australian cattle breeds. And published their results in late 2019. The test has been immediately adopted by some service providers.
A test to breed hornless cattle
In August 2010 a commercial test was offered to the beef industry for validation. In November 2013 an updated test using an additional nine markers was released making it more accurate across more breeds.
At the end of 2019, another round of optimisation was completed and published. This final optimised test performs well across Bos indicus, a major cattle species grown in Australia, and their crosses.
The current Australian Poll Gene Marker test is used to determine if an animal is 'true polled', that is, it carries two copies of the polled gene, and naturally lacks horns. Initially developed for use in Brahmans, the test can now be used with a high degree of confidence across a range of tropical and temperate cattle breeds enabling breeders to reduce the presence of horns in subsequent generations.