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by Gord Leathers
The pig's stomach has served it
well in the past but the single
chambered, simple sack that carried
a species through millions of years
and brought it to every corner of
the world is causing trouble for pig
farmers now.
The fundamental problem is
phosphorus. Too much of what
goes in the front is coming out the
back.
"One thing that you could say is
that typical pigs working with typi-
cal feed are more efficient at utiliz-
ing the nitrogen in the feed than the
phosphorus," says Don Flaten, a
professor of soil science at the
University of Manitoba. "It means
that when you're applying hog
manure, you need to be aware of
the potential to create an excess of
phosphorus in the soil."
It's the physiology of the pig that
brings this about. The first pig
rooted for tubers, shoots and small
animals during the Miocene period
about 40 million years ago. The
range stretched eastward from the
forests of Europe to the Mongolian
grasslands and south to the moist
jungles of India and New Guinea.
Some even made it to the plains of
Africa.
A voracious appetite and cosmopol-
itan diet made the pig very adaptable
and quite easy to keep as our ances-
tors found out about nine thousand
years ago. Opportunistic and
omnivorous, they probably foraged
in the village garbage dumps and
were eventually brought into the
fold as a food animal as well as an
effective garbage disposal. It wasn't
as versatile as the sheep or goat but
it was an efficient feeder and less
dangerous and demanding than the
wild cattle that would follow it into
domestication.
"Pigs are probably ranked right
up there with respect to their effi-
ciency," says Jim House, a swine
nutrition specialist at the University
of Manitoba. The baby pig is highly
efficient at converting nutrients into
lean tissue. Grower pigs are sort of
mid-range in their efficiency level.
They can usually convert about 1.0
kg of gain usually takes between
3.2 to 3.5 kg of feed."
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In this way the pig has served us
well, partly for the delicious assort-
ment of pork products from the
tasty hocks and chops to the tooth-
some Easter ham. It's also played
an important part in some serious
medical research. The sensitive
snout of the pig is still the instru-
ment of choice for the devoted truf-
fle hunter and there is even a small
pet pig industry.
But still the pig presents a prob-
lem. Unlike cattle, pigs have a sim-
pIe stomach, a monogastric, single
chamber that makes them less
capable of handling rough forage
because they don't have the same
bacterial aid in digesting plant tis-
sue that their bovid cousins enjoy.
The elegant bovid rumen is a
wonder of natural engineering, two
dark, moist chambers where several
species of bacteria thrive. The grass
eaten by the cow is thoroughly
processed by this microbial com-
munity, breaking down the cellu-
lose walls into simple sugars which
the cow can use. Other bacteria
extract nitrogen compounds and
still others produce phytase, an
enzyme that breaks down phytic
acid or phytin, the phosphorus-rich
molecule abundant in seeds but
found in other cells as well. In the
other two chambers these byprod-
ucts are processed further and pro-
teins, vitamins and minerals are
pulled from the stingy molecules of
rough forage.
The pig's digestive tract is
nowhere near as complicated and
doesn't handle rough forage as
well.
"Cattle are definitely better with
respect to utilizing fibre," House
said. "They can make better use of
phytate because of the compliment
of enzymes that they have in the
microbial mass within the rumen,
they can break down the phytin
phosphorus and make it more avail-
able."
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This leads to a fundamental
problem with modern, large-scale
hog farming. Pigs have trouble
breaking down phytin because they
don't have the symbiotic help from
bacteria that cattle do.
Consequently, hog feed must be
fortified with a phosphorus supple-
ment to help feeder pigs grow to
market weight quickly.
The result is a phosphorus-rich
manure which makes an excellent
fertilizer,The problem is that most
fertilizers are applied with nitrogen
in mind and doing that with hog
manure leads to an overdose of
phosphates which can leach out and
cause trouble in waterways. The
real trick is to adjust the pig's diet
so that it can extract the phosphorus
in the feed and use it for growing
pig tissue instead of pushing it out
the back, unused in the manure.
"So we're looking at strategies
that we can minimize the impact
that we have by reducing nutrient
excretion by tailoring diets to meet
the phosphorus needs of the ani-
mals," House said.
There are a couple of ways of
doing that. One is to use an inor-
ganic form of phosphorus such as
dicalcium phosphate where the pig
uses most, if not all, of the phos-
phorus. The other is to supplement
the diet with phytase, the enzyme
that cattle use to break down phytin.
Research has shown that
adding phytase to the diet signifi-
cantly cuts the need for dicalcium
phosphate and lowers the amount
of phosphorus in the diet by .1
percent. This lowers the phos-
phorus excretion by 20 to 30 per
cent.
"From a dietary perspective we
want to look at meeting the needs
of the animal so that we 're not
overfeeding phosphorus to mini-
mize nutrient excretion," House ,
said; "But you want to do so with
the realization that at the end of the
day producers need to be able to
make a profit to sustain their liveli-
hood." |