Clones spread top genes
By Jessica Buss
CLONING, such as that of the top bull Hanoverhill Starbuck, could offer big opportunities for livestock production, making valuable genetics widely available.
Pierre Laliberte, Semex Alliance director, Quebec, Canada, told the Semex Brave New World conference in Glasgow that the birth of Starbuck II in September 2000 had begun a debate on using cloning in cattle breeding.
The young bull was cloned from frozen cells taken from the high production and type sire Starbuck, used widely in the 1980s and 1990s, a month before he died in 1998. Semen from the clone has been collected since his first birthday, last September.
"There is no doubt that having more than one copy of a star bull would allow for a larger use of that bull and at a cheaper price." But in reality, it would be unlikely that two mature bulls would be producing semen at peak at the same time, as the procedure was likely to be expensive, limiting use to a few individuals.
For a proven bull to be cloned, he should first have highly superior genetic potential and there should be high demand for his semen or he could produce poor semen output. "But between deciding to clone a bull and the time when the cloned bull would produce semen, at least two years would go by," he said.
But there would be situations, such as when a top bull died at a young age, when he could be cloned to make his genetics available if some of his cells had been frozen, said Mr Laliberte.
One of the challenges of sire cloning would be controlling inbreeding. Presently, star bulls can sire several daughters and sons that will be sampled by AI centres. When a sire is successful with his second generation daughters, there will be several maternal grandsons of that sire entering AI.
Finally, about six years after a bull is first proven, the results of his sons are known. When he turns out to be an excellent sire of sons, several of them will be returned to service. Within the space of about 10 years, a specific sire can have considerable influence on his breed. "When that sire and his clones are used intensively, the risks of inbreeding are more real."
Even though the impact of cloning sires is greater, cloning females could also prove interesting. During 2001, two of the best show cows during the 1990s in North America, Lauduc Broker Mandy and Stookey Elm Park Blackrose, saw their clones born.
"It will be interesting to watch these heifers progress and to see how they compare with the original. Being able to reproduce a cow with exceptional type who was a winner at several shows is certainly a dream for many."
But even though they should have the same genetic potential as their famous original, it remained to be seen whether they would benefit from all the related environmental elements and develop in the same manner, he said.
"One advantage of cloning is the preservation of genes." The Holstein breed is becoming more dominant across the world and within the breed itself, lines are getting fewer. The consequence of such a concentration of genes, even though it may increase yields in the short term, may be harmful later due to accelerated inbreeding.
The discovery of the hereditary defect, complex vertebral malformation (CVM), more than a year ago was an excellent example, revealing serious consequences, added Mr Laliberte. Some countries estimated that Bell could be found in the pedigree of more than 75% of their Holstein cattle.
"But several endangered breeds within many animal species could be protected by freezing cells which can be cloned later as a partial solution to the problem."
Although not all breeds perform equally, they have their own characteristics which contribute to biodiversity. In several countries, associations are being created for the purpose of finding means to protect endangered species.
lFull conference report in next weeks issue. *
Starbuck II (pictured) will make the genetics of top bull Starbuck available once again , says Pierre Laliberte (above).
• Possible from frozen cells.
• Likely to be expensive.
• Useful for top sires.