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Feature

Beefing Up Cattle

Ruakura scientists are conducting world-leading research into agricultural applications of growth hormones.

Philippa Stevenson

If Snow White roamed the woods today, she would find it much harder to find seven dwarfs, as growth hormone treatment has eliminated virtually all forms of dwarfism.

The good news for dwarfs is also good news for New Zealand agriculture, according to Dr John Bass, leader of Ruakura Agricultural Centre's growth physiology group. As a result of the resources poured into solving human dwarfism, much useful research has become available to those investigating animal growth.

The growth hormone axis controls 30-40% of normal growth. The axis is the mechanism whereby the brain releases growth hormone, which prompts the liver to produce IGF-1 (insulin-like growth factor). This, in turn, acts on tissues to make them grow. The growth hormone can also act directly on bone and tissue. By using the growth hormone at various stages during an animal's development, researchers can control fat depositation, and produce an animal with a lean carcase and an enhanced rate of growth.

In many countries, however, injecting something into an animal which is going to be eaten -- even something which occurs naturally in the animal -- is unacceptable. As a result, the Ruakura team is studying other, more acceptable, uses for growth hormones, such as vaccination.

In immuno-neutralisation, an animal is vaccinated to inhibit growth-inhibiting hormones. Conversely, in immuno-potentiation, an animal is vaccinated to make the growth hormone more active. The result is vaccination for growth, a short-term therapeutic method which will allow farmers to regulate the growth and fatness of their stock, or to control the rate of growth of wool or hair.

Anti-idiotypic antibodies enable scientists to use specialised antibodies which mimic the action of the hormones, making hormone injections unnecessary.

Then there are all the possibilities of gene manipulation. While that may also ring alarm bells in some minds, Bass is convinced of the importance of the work.

"If we were totally prevented from manipulating animals, the result would be to increase starvation in the world."

The Ruakura group has some world-leading researchers, with strong overseas interest in their work. Their international reputation has proved useful, as it has gained them support from a number of major pharmaceutical companies, who have donated compounds that can cost more than $200,000 for five milligrams.

Bass predicts that, within his lifetime, the animals roaming the hills will be hardy, unprepossessing-looking things that produce a couple of offspring a year and forage for themselves in tough surroundings. They will have been implanted with biological switches which, with the flick of a dose of zinc or of a certain type of feed, will be able to produce an animal or fibre suitable for an identified niche market somewhere in the world.

Phillipa Stevenson is a freelance journalist.