BRAHMAN NEWS SEPTEMBER 2007 Issue #156
CSIRO Livestock Industries scientist Dr Kishore Prayaga has uncovered the technical and practical problems to breeding polled cattle and identified ways to increase the amount of polled animals in typical Australian herds. Looking into the genetic options to replace dehorning of beef cattle in Australia, Kishore has reviewed current world knowledge of polled gene genetics and with research and industry input is working towards developing DNA tests for identifying the genetic status of polledness using novel genetic technologies.
To avoid bruising, hide damage and other injuries – particularly in yards, feedlots and during transport, beef cattle are de‑horned. Horns pose injury risk to cattle handlers, allow dominance behaviour in the yards and cause handling difficulties in crushes and during transport. An invasive, labour intensive procedure in older calves, dehorning can also cause losses through secondary infection and in some cases, mortality. This routine practice is estimated to cost the industry more than $22.5 million a year. And in light of mounting animal welfare concerns, producers are keen to breed polled cattle as a non-invasive, welfare friendly alternative.
With a definitive genetic marker test to differentiate scurred, horned and polled animals likely to be developed within the next four years, producers may soon be breeding the horns off their cattle. While there is a complex interaction of the genes involved, producing a polled herd based on the preferential selection of polled breeding stock may provide the ability to permanently dehorn the national herd. This is particularly true for Bos indicus breeds which may contain the African horn gene.
Kishore estimates that by using conventional selection methods to produce a polled herd it may take more than 30 years in many breeds containing Bos indicus genotypes. But results from his simulated study suggest that location of genetic markers could reduce this process to about four to eight years.
He said the polled/horned condition was presumed to be under a relatively complex mode of inheritance through poll, scur and African horn genes segregating independently, but interacting with each other to produce polled, scurred and horned animals. "Molecular genetic studies have mapped the polled gene to a specific region on bovine chromosome 1, but the actual gene is yet to be located."
Achieving a polled herd is a complex process. The mode of inheritance and the expression of phenotype (animal characteristics determined by the genotype and its environment) are influenced by the animal’s sex, which complicates breeding decisions based on phenotypes alone. "A definitive DNA test for differentiating scurred, horned and polled animals is needed so that appropriate breeding decisions can be made earlier," Kishore added. "Information on any one gene is not effective enough due to the complex nature of inheritance."
Breeding polled animals is a harder task in some breeds, such as Brahman and Santa Gertrudis, because the horned gene is much more prevalent and the mode of inheritance is presumably more complex. "Propagating the polled gene in purebred herds has been hampered by the inability to distinguish between heterozygous and homozygous polled bulls," Kishore said. "If available, these genetic markers could be used in marker‑assisted selection strategies to increase the polled gene in breeding populations, even without knowing the actual location of the gene."
He said while breeding polled cattle provided a long-term solution to the horn problem and addressed the animal welfare concerns of dehorning, there was still resistance to the use of polled animals among some breeders who believe horned cattle are more productive than polled. "This perception is slowly changing and has been, to a certain extent, aided by animal welfare concerns associated with dehorning. Increasing awareness about the need for polled cattle is evident. Some stud breeders say they currently sell more polled bulls than horned bulls and that polled stock is considered more valuable."
The national cattle herd is estimated to be about 52 per cent horned with 47 per cent polled and one per cent scurred. Among the major breeds about 90 per cent of Brahmans and Santa Gertrudis are horned, while the combined Hereford and Poll Hereford figure is about 50 per cent.
Eddie and Debbie Streeter, who own and operate Fairy Springs Brahman Stud, participated in Kishore’s research project. As part of the Beef Cooperative Research Centre (CRC) study to identify genes influencing the horns status in cattle, 10 pregnant cows with a potential to produce scurred and polled calves were transferred from the Streeter’s northern Queensland property, White Kangaroo Station, west of Bowen, where they run their breeders and younger heifers. The cattle were taken to CSIRO’s Belmont Research Station near Rockhampton in November 2006.
"Tissue samples from the horn region of the newly born calves were collected for further analysis," Kishore said. "After the sampling was finished in March this year, the cows and calves were returned to Fairy Springs. This is an example of industry and R&D organisations working hand in hand to find novel solutions to industry issues."
At the Fairy Springs Brahman Stud, 200 kms south-west of Rockhampton, the Streeters run bulls, producing more than 80 for sale each year. They also own and operate Coolamondah, south of Monto in the North Burnett region, where they fatten steers – and eventually bulls as more come online. Eddie and Debbie’s son, Joe, manages White Kangaroo Station (recently purchased to expand their operation) where they run 1100 females, including 200 red stud females. Their daughter, Sarah, is a pastoral technical officer with the Northern Territory Department of Primary Industry, Fisheries and Mines based in Tennant Creek.
With an increasing demand for polled bulls, the Streeters are joining more polled bulls to their cows each year. Eddie and Debbie have been breeding polled bulls for a number of years and have produced more than a 50% polled herd. "We try to keep quite a few polled bulls in our herd and buy them when we can." The Streeters concentrate on using sires that breed females with longevity, are highly fertile and have good udders. Their aim is to achieve maximum fertility from low maintenance cattle that have the ability to reproduce high quality meat.
"Our most significant purchase was at Charters Towers in 1998 when we bought, Huonfels Jacob Rio," Eddie said. "He is a red polled sire with predominately American bloodlines and is crossing extremely well with Australian bloodline Fairy Spring’s cows. The progeny of Jacob Rio have dominated the red bulls offered at Brahman Week over the past few years, obtaining the top red average three years in succession and topping the sale in 2002 with the $55,000 polled sire, Fairy Springs Beaumont. At the Charters Towers Big Country sale in February this year, the Streeter’s topped the red secton of the sale with a polled bull that sold for $40,000 and last year sold a half share in the polled Fairy Springs Red Leader for $48,000.
From an industry perspective, Kishore said beef producers were divided over the issue of polled animals and there were several concerns about their breeding. "Most scientific studies have demonstrated a lack of difference in growth, reproductive performance, mortality, carcass and behavioural traits between polled and horned animals in Bos taurus breeds. It’s encouraging to note that there is a growing understanding of animal welfare concerns regarding dehorning and many breeders are interested in a decisive DNA test to identify homozygous polled bulls."
He said the most significant case against the use of polled cattle in the Bos taurus breed was the evidence of some association between the polled gene and bull soundness issues such as premature spiral deviation of the penis and the preputial prolapse. "This needs to be further investigated and if proven correct, remedial measures need to be identified," he explained. "Performance comparisons of polled and horned animals in various beef cattle breeds are needed to counter the perceptions associated with poor performance of polled animals."
Kishore said the polled/horned condition is under a complex mode of inheritance in Bos indicus breeds through polled, scurs and African horn genes segregating independently, but interacting with each other to produce polled, scurred and horned animals. Molecular genetic studies have mapped the polled gene to a specific region on bovine chromosome 1, but the actual gene is still to be located. "Scurs and African horn genes have not been studied thoroughly at a molecular level. With the current advances in molecular genetics and statistical methods, new research programs to develop DNA tests for identifying homozygous/heterozygous animals for polled, scurs and African horn genes to assist in faster introgression for the polled condition into beef cattle populations are needed.
"The best alternative to the invasive procedure of dehorning is breeding polled cattle. This would provide a long-term solution to the problem of horns and at the same time, address the animal welfare concerns of dehorning." And while turning out a polled herd is not as straightforward as previously thought, with a better understanding of the genetic control of polledness and a definitive DNA test for polled alleles becoming available, breeding horns away in each breed will be achievable. "The process would be gradual, needing the active involvement of the big breed associations and the implementation of concerted research and extension strategies."
The research project, led by Kishore, is supported by Meat and Livestock Australia through the Beef CRC. For more information: Dr Kishore Prayaga, 07 49238 210 or
Further reading: Genetic options for replacing dehorning of beef cattle in Australia – final report from project AHW.094 – available free from MLA website www.mla.com.au