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ABSTRACTS
Earlier work on vaccination against foot-and-
mouth disease, though extensive, was quite un-
successful. The use of formolized virus by French
workers, however, showed that the prospect was not
altogether hopeless. This vaccine was intensively
studies by workers in various countries and in
Germany it was found that the vaccine could protect
100 per cent of guinea-pigs and 66 per cent of cattle
against generalization of the infection. This method
was, however, unsuitable for field application as a
considerable proportion of batches of the vaccine
were infective. The optimum concentration of formol
lay within such a narrow range that on one side the
vaccine was often infective and on the other it failed
to protect ; this optimum could not be constantly
attained. Recently, some Danish workers studied
the adsorption of this virus on aluminium hydroxide
and found that, under certain conditions, the adsorp-
tion was so strong that the virus could not generally
be eluted by chemical means ; and, by subcutaneous
inoculation in guinea-pigs no disease, but immunity,
was set up, the degree of which corresponded with
the quantity of adsorbate injected. On intracuta-
neous inoculation into the foot-pads, however, the
adsorbate was still infective but this infectivity
could be removed by heating at 25°-37°C. without
loss of immunizing property. When used in cattle
such a vaccine set up the disease instead of immu-
nizing and the results could have no practical appli-
cation.
Such was the state of affairs when work on the
problem was begun at Riems (The German Foot-and-
mouth Disease Research Station is situated at the
Baltic island of Riems, off the coast of Greifswald).
Earlier Work confirmed the findings of Danish workers
and a constantly safe and useful vaccine for cattle
could not be made even by more prolonged incuba-
tion. This difficulty was overcome by the addition
of 0.05 per cent formalin and 48-hour incubation at
25°C. which sufficed to make a constantly safe and
efficient vaccine. This work showed that a solution
of this difficult problem had been provided by the
action of formalin on the virus stabilized by adsorp-
tion. The vaccine has been used on over three
million animals in the field ; none of them developed
the disease. Some of the inoculated animals when
infected 10-14 days afterwards proved immune to
massive infection.
The method of preparation of the vaccine is des-
cribed in detail under the following headings. The
interested reader should refer to the original : (1) Ob-
taining the virus including choice of production
strains and method of infecting the virus-producer
animals ; (2) Preparation of the virus containing
material for incorporation in the vaccine ; (3) Mixing,
drawing off and incubation of the vaccine; (4)
Chemical test of the various reagents required and
the vaccine itself ; and (5) Biological test of the
vaccine for safety, bacterial contamination and
immunizing capacity. [ M. A.]
Fertility and hatchability when the environ-
mental temperature of chickens is high. BURT
W. HEYWANG (1944). Poultry Science 23, 334
THE influence of high environmental temperature on
the fertility and hatchability of eggs laid by White
Leghorn pullets has been investigated. The birds
were kept at normal, rather than at artificially
controlled, temperature conditions. They were
trapnested and the eggs, collected from the nests at
hourly intervals, were kept in a refrigerator at 55°F.
till incubated. They were saved for incubation on
the six week days and placed in the incubator the
following Monday, during 12 periods between March
29 and August 21, 1943. During this entire period
the same White Leghorn cockerels remained with the
different groups of pullets.
The data on fertility and hatchability were grouped
into six lots depending upon whether the eggs were
saved during a period when the maximum tempera-
ture was between 80°-84.9°, 85°-89.9°, 90°-94.9°
95°-99.9°, 100°-104.9° or 105°-109.9°F. The average
for each of the ranges was determined from the
individual figures of the period.
The figures for eggs laid by 108 pullets, when
examined, showed that when the average maximum
environmental temperature was 82.8°. 86.2°, 93.0°,
97.5° and 101.8°F., the fertility of their eggs was,
respectively, 91.9, 93.6, 91.8, 88.8 and 82.9 per cent,
and the percentage of chicks hatched from their
fertile eggs was, respectively, 78.9, 77.7, 78.4, 71.8
and 68.0.
The eggs laid by 63 pullets of the above group,
when the average maximum air temperature was
106.8°F., were also incubated. The average figures
of fertility and hatchability for this set of birds,
when the average maximum environmental tempera-
ture was 82.8°, 86.2°, 93.0°, 97.5°, 101.8° and 106.8°F.,
were, respectively, 92.5, 92.4, 91.6, 86.8, 80.4 and
73.8 per cent for fertility, and 78.8, 79.3, 78.5, 72.2,
67.9 and 55.1 per cent for hatchability from fertile
eggs.
The experimental results were analysed statistically
and p was determined for the fertility and hatchabi-
lity of the eggs laid at different environmental
temperatures. This showed that at the average
maximum temperatures of 101.8° and 106.8°F.
fertility and hatchability were significantly lower
than those of the eggs laid at the average maximum
temperatures of 82.8°, 86.2° and 93.0°F.
It is therefore concluded that fertility and hatch-
ability are lowered when chickens are kept under
high environmental temperatures. [ T.S.K.]
Studies in bovine mastitis—Modes of spread
of Streptococcus agalactiae infection in dairy
herds. A report on observations organized by