The Rural Voice, 1989-04, Page 50NEWS
PORCINE SOMATOTROPIN - PST - COULD REACH MARKET BY 1990
Pork producers in Canada might
have the option of using porcine soma-
totropin (PST) by as early as the middle
of next year, says Dr. Roger Hacker of
the University of Guelph's Department
of Animal and Poultry Science.
And he predicts that PST could in-
crease the carcass index for hogs in
Ontario by an average of about three
grading points.
Dr. Hacker, who is working on a
series of studies of PST, says the re-
search work will probably be completed
before the end of 1989. The projected
treatment with PST is an implant put in
a pig's ear six weeks before market, he
says. And should the pig not be ready for
market at the end of six weeks, a weekly
implant would also be available. A six-
week implant would probably release a
dose of about four to five mg a day.
"Monsanto is the leader in that tech-
nology," Dr. Hacker says. Monsanto,
with its head office in St. Louis and
Canadian branch office in Mississauga,
has already approached the federal
government to initiate the approval
procedure, he says.
Two studies of PST have already
been completed at Guelph. The first, for
the International Minerals and Chemi-
cals Corporation based in Indiana
(whose pharmaceutical company is
Pitman -Moore), was carried out in con-
junction with Ridgetown College of
Agricultural Technology.
The large study included 130 pigs,
half of them treated and the rest as the
control group. The results, says Dr.
Hacker, were "very positive." There
was a reduction in backfat, saturated
fatty acids were reduced about 20 per
cent, and lean meat content increased 10
per cent.
In the second study, for Monsanto,
pigs were fed a 16 per cent protein ration
with no added lysine and only 24 mg of
PST a week. Results showed a 20 per
cent reduction in fat and a growth rate
increase of about 5 per cent. Feed effi-
ciency improved by about 20 per cent.
A third study, now underway for
Monsanto, is examining the effects of
PST on reproduction. Gilts are being
fed an 18 per cent protein ration with
added lysine and 36 mg of PST a week.
48 THE RURAL VOICE
The study should establish the influence
of PST on reproductive capacity should
a farmer use PST on a gilt to improve
leanness and later breed the gilt.
A similar study done in Saskatche-
wan found that gilts given PST bore
more piglets, Dr. Hacker says, but in that
study pure somatotropin extracted from
a pig's pituitary gland was used rather
than a recombinant PST product (re-
combinant product is produced using
the growth hormone gene placed in
bacteria and multiplied).
Various studies of PST have come
up with various results. Dr. Jim Nelssen
of Kansas State University, who spoke
at seminars sponsored in Ontario last
month by Shur -Gain, reports that a
"correct" nutritional regimen for PST -
treated pigs can help to produce an in-
crease in average daily gain of 38 per
cent, a 35 per cent improvement in feed
efficiency, and a lowering of carcass fat
by 45 to 63 per cent.
But when assessing such results, Dr.
Hacker says, always consider three fac-
tors: what the pigs have been fed, what
dose was given (treatments can vary by
30 to 70 mg a week), and what type of
pigs were used.
Researchers sometimes "try to
grandstand," he says, but "When it
shakes out in the industry I seriously
doubt if you're going to get growth rates
of 30 per cent increase."
The product is too expensive to be
used to achieve "astronomical figures,"
he says, and at extremely high levels
PST may cause side effects such as
stiffness in the joints. At extreme levels,
PST can shut down fat creation, Dr.
Hacker says, and thus dries up the lubri-
cant in the pig's joints.
Dr. Ron Ball, also of Guelph's De-
partment of Animal and Poultry Sci-
ence, has also been involved in the PST
research. PST, he says, is a protein
hormone with 191 amino acids, and is
very different from sex hormones,
which are steroids.
Sex hormones are fat soluble and can
be absorbed from the intestine intact and
stored in fat tissue. PST, on the other
hand, is broken down by digestive en-
zymes and leaves no residue.
The furor over bovine somatotropin
(BST) in recent months, Dr. Ball says, is
politically motivated. "I think the safety
issue is being used by the people in the
dairy industry almost as a red herring,
when what they're really concerned
about is the supply management sys-
tem."
Like BST, PST is "probably the saf-
est product we've ever considered look-
ing at," he says.
Dr. Hacker agrees wholeheartedly.
"You can drink a glass of it and it
wouldn't do anything to you," he says.
It's good that information is reported
in the press, he adds, but care should be
taken that the report is factual.
Pork producers have so far been
quite receptive to PST, Dr. Hacker says,
but the BST issue has confused politics
and science. Dairy farmers may worry
about the effects of increased produc-
tion on their industry, he says, but they
could keep five fewer cows. Yet they
don't want to keep five fewer cows
because they want those cows to pro-
duce calves that they can sell.
Monopolies, Dr. Hacker adds, re-
quire checks and balances. "We really
have to ask ourselves, 'Are they in the
best interests of society?' Because I
think that's the basis of this issue with
BST."
At the University of G uelph, another
PST study, this one to test dose re-
sponse, will begin at the end of this
month in conjunction with Monsanto
and as part of the requirements for fed-
eral government approval of the prod-
uct. This work will be supplemented by
some reversion studies to assess how
fast pigs will build up fat after PST is
withdrawn, Dr. Hacker says.
What remains an unknown factor is
the retail cost of the product.OLG