Evaluating Response
SINCE 1970, virulent strains of New
castle disease have produced severe
worldwide losses in poultry. If the dis
ease becomes so widespread in the
United Stales that it cannot he eradi
cated, an economical means of eval
uating vaccination procedures will be
come necessary.
Present methods of vaccination have
had highly varied results. Scientists
think this extreme variability may be
due to the particular strain and po
tency of the vaccine as well as the route
of administration.
In studies at ARS’ Southeast Poultry
Research Laboratory in Athens, Ga., a
simple and rapid microtest procedure
was evaluated for measuring response
of poultry to Newcastle vaccination.
During a year’s application in at least
one large diagnostic laboratory in Geor
gia, the manual-miciotest hemaggluti
nation-inhibition (HI) procedure
proved to be a very satisfactory com
promise between the old test tube
method fmacrotesting) and a highly
automated and expensive microtest
method. The automated microtest
method uses a machine costing $5,000
to 86,000 which automatically adds re
agents and makes the dilutions.
Hemagglutination (HA) is the
clumping reaction of red blood cells
when suspended in a liquid that con
tains Newcastle disease virus. Specific
antibodies directed against that virus
will inhibit the hemagglutination.
ARS researchers employed commer
cially available manual microtest equip
ment in conjunction with inactivated
HA antigen in the modified procedure.
In many laboratories, the HI test often
involves highly virulent HA antigens
which may serve as a source of con
tamination in virus isolation attempts.
Blood samples were obtained with
syringe and needle either from the wing
vein of the chicken or by cardiac punc
ture and then placed in tubes treated
with a silicone solution to aid in clot
release. After clotting was adequate and
the serum had been chilled at 4° C.,
sometimes overnight, it was harvested
with disposable glass pipettes and
placed in microtest plates.
Similar plates were prepared for
serum dilution by adding antigen-saline
mixture to each well. The sera were di-
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To Newcastle Vaccine
luted until there was lack of inhibition
of agglutination—evidenced by a dis
tinct “button” of red blood cells in the
bottom. From this end point the anti
body titers were determined.
Using stock inactivated antigen and
washed red blood cells which have been
piepared in advance, an experienced
technician can test as many as 700 sera
in approximately 7 hours.
The serum-storage plate, developed
by Southeast Poultry Research Labora
tory scientist Dr. James E. Williams
and biological laboratory technician
Alton D. Whittemore, occupies min-
American Model Crop Dryer
Because of the additional
acreage planted this year,
major grain growers are
turning to larger capacity
crop dryers. One that is
proving extremely popular is
the American Model 2420.
According to the
manufacturer, the 2420 can
dry up to 11,400 bushels in 24
hours, removing 5 points of
moisture, from 20 percent to
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Lancaster Farming, Saturday. Sept. 7,1974 —
imum frce/cr space and allows simul
taneous pickup .and dilution of 12 sera,
utilizing 12 microdiluters to each
mi< rodilutcr handle.
Equipment costs are If' times less
for the compromise manual method
than for the automated microtcst
method.
Described by veterinary medical offi
cer Charles W. Heard and biological
laboratory technician William J.
Wilkes, the procedure also affords sav
ings in reagents and makes possible a
reproducible determination of antibody
levels in serum.
15 percent. The dryer is ideal
for com, milo, beans, other
grains and seeds.
One of the outstanding
features is the completely
automated operation. As
long as wet grain is
available in the holding tank,
the dryer will continue to
cycle automatically...filling,
drying, cooling, emptying
and refilling. Controls may
be set for a specific drying
period and a separate
control regulates the grain
cooling time. These can be
easily changed to meet -
varying conditions of the
grain or weather. The im
proved controls are located
on the dryer in a tamper
proof box.
Another unique feature of
the Model 2420 is the cycling
burner. This provides an
ideal drying climate for the
grain since the moisture is
removed by a sweating
process rather than a con
ventional continuous
“baking” process. Alternate
short bursts of hot and cool
air move through the 12”
drying column. Moisture is
removed rapidly while
maintaining a lower kernel
temperature wheich aids in
maintaining grain quality.
The 2420’s twin burners
can generate up to 12 million
BTU’s of heat and 10 hp fan
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motors move the heated and
cooling air the full length of
the dryer. Fans are
automatically shut down
during the filling and emp
tying cycles. This keeps air
pollution to a minimum.
The American Farm
Equipment Company has a
complete line of dryers
ranging in capacity from
1,400 to 36,000 bushels per
day. These are available on a
purchase, lease or rental
basis. The company has
authorized distributors
throughout the major grain
producing areas of the
United States.
For additional information
on prices, contact the
American Farm Equipment
Company, 340 East Main
Street, Lake Zurich, Illinois
60047.
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Any of the ground leftover
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celery and one teaspoon prepar
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