Nutrition & Health
Feedstuffs, January 30, 2012
11
Transito rapido tied to soybeans
Using a urease activity range to determine soybean
meal quality may need to be reconsidered based
on field observations of trypsin inhibitor levels in
supposedly good-quality soybean meal. This article
documents a potential cause of a syndrome
known as transito rapido.
By NELSON RUIZ*
I
N 1944, Caskey and Knapp devised
a method to detect inadequately
heated soybean meal using the
activity of the naturally occurring
urease enzyme that is present in
soybeans.
The presence of urease after
soybean meal processing was used
as an indirect marker to indicate the
presence of the main anti-nutritional
factors in soybeans: trypsin
inhibitors.
The method is fairly simple,
straightforward and consistent and
is based on urea’s transformation
by urease into carbon dioxide and
ammonia. Because ammonia is a
base, its release during the reaction
causes a rise in the pH of the test
solution (delta pH or pH rise), which
can be easily determined.
For decades, the range of change
in pH units from 0.05 to 0.20 has
served as an indicator of adequate
soybean meal processing. When the
change in pH was fewer than 0.05
units, there were concerns that the
soybean meal had been overheated;
if it was more than 0.20 units, the
soybean meal was underheated and
trypsin inhibitors were still active.
Through the years, this upper
limit of pH change has been
questioned, and suggestions
have been made that it should be
increased. For instance, Hayward
(1975) proposed that the upper
limit be set at 0.30, and Waldroup
et al. (1985) suggested that it be
raised even further to 0.50 units
of pH change. In Brazil, animal
feed manufacturers use 0.30 pH
units as the upper limit to indicate
the adequacy of soybean meal
processing (Penz and Brugalli,
2000).
For nearly 70 years, this simple
“urease activity range” has served the
animal feed industry, especially the
poultry and swine industries, and has
basically gone unchallenged in the
quality evaluation of billions of tons
of soybean meal.
Today, the urease activity range is
still relied on to evaluate the quality
of more than 100 million tons of heatprocessed soybean meal produced
worldwide each year.
The time has come to reconsider
the use of this simple change in pH
— particularly the upper limit — as
the standard method of determining
the adequacy of soybean meal
processing.
Field observations of negative
consequences have prompted a
new range to be proposed for use in
the poultry industry. The following
article will provide valid reasons for
why reconsideration is now highly
appropriate for the poultry industry.
Review
In 1969, Kakade and co-workers
published the first chemical
method for the consistent direct
*Dr. Nelson Ruiz is with Nelson Ruiz
Nutrition LLC in Suwanee, Ga.
January 30, 2012.indd 11
measurement of trypsin inhibitors
present in soybeans, and after several
modifications by different authors,
a number of methods currently
are available for the accurate
measurement of trypsin inhibitors.
However, the determination of
trypsin inhibitors is not as easy
and straightforward as determining
urease activity.
By 1987, Dale et al. demonstrated
that the lower urease activity range
breakpoint was baseless because the
minimum pH value for the reaction
was zero in the absence of urease
in soybean meal. These researchers
were able to show that no correlation
was found between the performance
of broiler chicks and that zero value
for urease activity.
To explain the poor performance of
some of the chicks at the zero level
of urease activity, another technique
— the solubility of the protein in
potassium hydroxide — was needed.
Today, the poultry industry
is well aware of the negative
issues associated with poor bird
performance when overheated
soybean meal is included in the
feed. Numerous publications in the
scientific literature have documented
that the digestibility of amino acids,
especially lysine, is severely affected
when soybean meal has been
overprocessed.
Also, the negative issues associated
with underheated soybean meal,
which arise from the presence of antinutritional factors, especially trypsin
inhibitors, are well documented and
understood.
A major contribution the global
oilseed industry could make to
the poultry industry would be to
acknowledge and accept that the
upper limit of the urease activity
range has no place today as a
major contributor to determine
the quality of soybean meal. The
global poultry industry is presently
experiencing problems associated
with soybean meal quality that
have arisen from continually
placing too much confidence in
the upper limit of the antiquated
urease activity range.
Test questioned
For many years, the upper urease
activity range limit was believed and
accepted to be correct because it had
been used by and served the poultry
industry for decades.
As far as the lower limit of the
range (0.05 pH units) is concerned,
the late Dr. Felipe Consuegra (former
poultry nutritionist for Ralston
Purina in Colombia) explained the
importance and practical value
of using the potassium hydroxide
protein solubility (KOHPS) test
almost 10 years before the test was
presented by Dr. Nick Dale at the 1987
Georgia Nutrition Conference.
The KOHPS test was developed and
used by Ralston Purina, but it was
never published or presented at a
professional meeting.
As early as 1979, it was known
that commercial soybean meal lots
displaying a pH rise of 0.0 did not
OUTBREAK SIGNS: A transito rapido outbreak is when broiler droppings
lose their normal shape and consistency, do not display the characteristic
white uric acid cover, contain undigested feed that is visible to the naked
eye, usually have a yellowish-orange color, are frequently watery and contain
sloughed intestinal tissue.
necessarily mean that they were
being overheated.
Transito rapido
In 1998, while I was involved with
the Venezuelan operations of
Continental Grain Co., a shipment of
more than 7 million metric tons of
soybean meal originating from South
America arrived at two feed mills.
Within a couple of days after this
soybean meal was formulated into
broiler feeds, every broiler farm that
received feed containing soybean
meal from that shipment experienced
an immediate and severe outbreak
of the syndrome commonly referred
to as “transito rapido” (rapid feed
passage).
A transito rapido outbreak is
when broiler droppings lose their
normal shape and consistency, do
not display the characteristic white
uric acid cover, contain undigested
feed that is visible to the naked eye,
usually have a yellowish-orange
color, are frequently watery and
contain sloughed intestinal tissue
(pictured). Broilers in a flock
experiencing a transito rapido
outbreak have extremely dirty
feathers, lack bodyweight uniformity
and display poor pigmentation, and
upon necropsy, proventriculitis is
frequently observed.
As a consequence, the litter
becomes wet and slippery, feed
conversion is negatively affected,
bodyweights are lower than the
desired standard and considerable
economic losses may be realized.
Kouwenhoven (1992) has described
a similar condition as a lymphocytic
proventriculitis of infectious origin.
The syndrome has also been
characterized as malabsorption (ter
Huurne and Smits, 1999).
In the 1998 Venezuela outbreak,
after one week from the onset, it
was suspected that the new lot of
soybean meal may have been the
cause, which prompted a decision to
immediately remove that shipment of
soybean meal from the feed formula.
Within 48 hours after the soybean
meal was removed, the transito
rapido outbreak began to subside and
eventually disappeared completely.
Routine analyses — including
KOHPS, urease activity and proximate
analysis — of the soybean meal
were performed, but the results did
not reveal anything abnormal. Also,
necropsy of several birds revealed no
signs of an infectious agent.
Samples of the soybean meal
were brought to the U.S. for trypsin
inhibitor analysis (using the American
Organic Chemistry Society method)
and for the analysis of 21 different
mycotoxins, 10 biogenic amines and
other suspected responsible agents
that may have caused the transito
rapido problem. Again, the results
yielded nothing unusual.
There was no reasonable
explanation for the transito rapido
outbreak, and no one knew what to
do with almost 7,000 mt of soybean
meal that remained in storage.
Several fairly similar outbreaks
occurred in other Latin American
countries, especially Mexico, toward
the end of the 1990s and in the
beginning of this century.
One lesson from these outbreaks is
that soybean meal is always involved.
Decreasing the inclusion level of
the lot of soybean meal involved
in a given outbreak or switching to
another lot from another supplier
seems to completely stop the transito
rapido outbreak.
Trypsin inhibitors
So, what does all of the previous
discussion have to do with the
original suggestion that the urease
activity range is outdated?
Most of the outbreaks that have
been thoroughly investigated are
related to the presence of excess
trypsin inhibitors in commercial
lots of soybean meal and/or fullfat soybeans that have been
inadequately processed.
• Continued next page
1/26/2012 2:44:29 PM