A vaccine as an option to common animal castration methods has been
kept on the laboratory shelf by expense and regulatory hurdles.
More than 10 years ago, the Veterinary Infectious Disease Organization
in Saskatoon began working on a way to replace traditional castration
with a process that made animals allergic to their own fertility.
“Reduced time for producers to castrate animals, reduced stress on the
animals, no weight loss after castration, which takes place with (other
methods) and reduced risk of infection,” are potential benefits, said
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Chris Huxsoll, a researcher at the University of California at Davis
who has continued work on immunocastration.
“We have also found that immunocastrated animals grow faster than other
steers. With our immunization procedure, carcass quality and aggressive
behaviour are similar between immunocastrated animals and steers
(conventionally cut).”
Huxsoll said immunocastration has not caught on partly because of
problems with the adjuvant that is needed to deliver the genetically
modified vaccine.
“More research will provide alternatives for delivery. I believe there
may be a way to overcome the cost and adjuvant limitations of our
current vaccine if I can obtain funding for further research.”
John Kastelic, an Agriculture Canada livestock scientist in
Lethbridge, has also studied the concept and agreed that the product
may have potential if the cost of development and licensing can be
overcome.
“The vaccine itself is superb,” Kastelic said. “We got great results in
testing, and its design is really unique and so effective.”
The drug, created by Biostar, a former VIDO spinoff, stops the
reproductive process early in the chain of physiological events that
result in the development of a sexually mature animal.
Sex hormones initially develop high in the brain at the hypothalamus. A
tiny, vulnerable, 10-amino acid peptide called GnRH, or
gonadotropin-releasing hormone, is released from the hypothalamus in
minute amounts and travels within the brain to the pituitary gland.
Like a micro switch that triggers a larger switch, the pituitary
releases greater amounts of hormones, which in turn trigger other
glandular releases of even larger volumes. These hormones result in
development of mature sexual organs and systems.
The immunocastration vaccine turns the animal’s immune system against
the GnRH, stopping the chain of events.
The vaccine is created by attaching the GnRH molecule to a few foreign
molecules that can easily be identified as being out of place in the
body. The animal’s immune system will then take exception to any GnRH
that it finds and wipe it out.
“Stopping the process so very early on is incredibly effective,”
Kastelic said.
Murray Jelinski, who used to be involved with Biostar, said creating a
vaccine such as the GnRH inhibitor is relatively inexpensive once the
gene sequence is known. The difficulty comes in the product evaluation
stage.
While vaccines that fight illness move quickly through the federal
approval system, Jelinski said drugs such as an immunocastration
vaccine take considerably more time and expense because they change
animals’ physiology.
“I’m sad to say we haven’t done much with the cattle side of the
research,” said Jelinski, whose company MetaMorphix owns the part of
BioStar that developed the vaccine.
“We’ve been working on it with cats. Companion animals are seen to have
a much greater potential market. The biotech sector is under a lot
pressure from the markets these days and we are no exception. We are
being very prudent in our approach to research.”
Jelinski said the product still requires research before it can be
submitted to Health Canada.
“We found it was difficult to get a good long-term immune response with
bovines, but that isn’t to say with some more work it wouldn’t be
there.”
He said the vaccine’s vulnerability makes it safe for human
consumption. Even if it survived in meat as a residue, he said, it
would be destroyed in the digestive tract.
