Cloned animals dying at NZ AgResearch

14.11.2002 New Zealand Herald

By SIMON COLLINS

Almost a quarter of the calves and lambs cloned from adult animals by
Government-owned AgResearch® have died within about their first three
months of life.
    AgResearch®'s cloning programme leader, Dr David  Wells, said "errors
in the pattern of gene expression" had produced some animals  with
deformities that made them "not viable at birth".  The institute had also
aborted some calves before birth, and slaughtered some cows acting as
surrogate  mothers when foetuses grew too big to be born normally.
Scientists performed  caesareans to deliver others.
   But he said that in 35 cases so far where cloned  calves had lived and
produced their own calves by normal sexual reproduction,  there was no
evidence that defects had been passed on to the next generation.  The
Hamilton institute said yesterday that it had begun work on genetically
modifying cows' milk to produce potentially valuable medical drugs, in line
with  a controversial permit granted in September.
   The institute claims to be the most efficient in the world at cloning
animals, achieving a 6 per cent survival rate of cloned  embryos through to
weaning at about three months.
   Dr Wells said "the vast majority" of cloned calves  were delivered
naturally by surrogate mothers, but "large offspring syndrome",  where
cloned foetuses can grow up to a third larger than normal, "can sometimes
happen".
   "We aim to deliver appropriately sized animals.  If  there are difficult
births, they may need assistance in delivering animals, and  in extreme
cases there may be a need for a caesarean section to deliver a calf.  But
they would constitute certainly perhaps 5 per cent of pregnancies."  When
cases were detected in time, they were aborted.
    "We are constantly monitoring pregnancies and  detecting any that we
suspect are developing abnormally, and we would either  terminate that
pregnancy early in gestation ... or we may sacrifice the cow to  recover
the material for further scientific study."
   He said it would not be meaningful to state a  maternal death rate
because the decisions to abort the calf or kill the cow were  made by the
scientists.  However, the death rate of cloned calves between birth  and
weaning was 24 per cent, compared with about 5 per cent in normal calves.
    Of these, about 2 per cent were put down because of  chronic sickness,
and the rest died unaided.  A further 5 per cent died after weaning,
compared  with about 3 per cent among calves born normally.