220
Studies on the Determination of Digestibility coefficients
and temperature and may be carried to almost
any distance according to the force and direction
of the prevailing air currents. This explains
why contact must be fairly close in order to
catch an infectious disease. A fine droplet mist,
though more persistent, is generally too dilute
to do harm. Thus dosage of infective material
is an important factor in transmission of air-borne
diseases.
The effective dose also varies rela-
tively and actually with every member of the
herd and with every species and strain of bac-
teria, because each individual has a special
resistance which can deal with particles of the
infective agent below a certain minimum but
variable number.
Most field strains of rinderpest are presumably
of a highly virulent nature and are associated
with high mortality and their wide prevalence
is probably at least partly dependent on such
factors as are discussed in this paper. On the
other hand, it may be noted that so far there
is only one outbreak of rinderpest on record—
and that of very mild intensity—which could be
attributed to goat virus, a remarkable fact in
view of the wide spread use of goat-adapted
virus for immunizing cattle in India. This
tends to support the observations above on the
transmission through the breath of the less viru-
lent goat-adapted virus in bulls.
SUMMARY
Hill-bulls infected with a virulent strain of
rinderpest virus are capable of transmitting the
disease by the expired air when exposed to
healthy
animals.
Under the experimental
conditions used a minimum of six hours exposure
and a distance of six feet between infected and
healthy animals were necessary for positive
results. The breath of bulls artificially infected
with the virulent strain is infective by the fifth
day. When, however, air in a semi-enclosed
space become charged with virus, a sufficient
quantity to infect may be taken up in at most
15 minutes by a susceptible animal breathing
that air.
Rinderpest was not transmitted to bulls under
normal conditions either by a less virulent strain
or by goat-adapted virus.
ACKNOWLEDGEMENTS
I am grateful to Dr F. C. Minett and Mr.
J. R. Haddow for their suggestions.
REFERENCES
Bhatia, H. L. (1935). The Role of Tabanus orients
Wlk. and Stomoxys Calcitrans Linn in the mechani:
cal transmission of rinderpest. Indian J. vet. Sci.
5, 2
Cooper, H. (1932). Rinderpest Transmission of In-
fection by Contact. Indian J. vet. Sci. 2, 383
Curasson, G. (1922). Les Insectes Piqueurs peuvent—
ils transmettre la Peste Bovine. Rev. Gen. Medc.
Vet. 31, 57. (Abs. in Rev. app. Ent. 1922. 10, 159.)
Dudley, S. F. (1928). Microbic dissemination in schools.
Lancet. 215, 849.
Hall, Norman. G. (1935). Investigations on rinderpest
Immunization. Thesis. H. Roth/Zurich 2, Todis¬
trasse 67
Hornby, H. E. (1926). Studies in rinderpest immunity :
(2) Methods of infection. Vet. J. 82, 348
Hutyra, F., Marek, J. and Manninger R. (1938). Special
Pathology and Therapeutics of the Diseases of Domestic
Animals. (Fourth Edition) Bailliere, Tindall & Cox.
London 1. 256.
Sen, S. K. (1925). Experiments on the Transmission of
Rinderpest by means of Insects. Mem. Dep. Agric.,
India, Ent. 9. 59
STUDIES ON THE DETERMINATION OF DIGESTIBILITY COEFFICIENTS
III. SINGLE TRIAL METHOD FOR THE DIRECT ESTIMATION OF INDIVIDUAL
DIGESTIBILITY COEFFICIENTS IN A MIXED RATION*
By INDU BHUSHAN CHATTERJEE, M.Sc. (Agr.), L.Ag. (Animal Nutrition Laboratory, Dacca)
(Received for publication on 13 December 1943)
THE estimation of the respective shares of
digestibility of individual feed and feed compo-
nents in a mixed ration offers a problem which
so far has been only partially solved. The
matter is much simpler when it involves a single
feed, since, by assuming the faeces as indigest-
ed residue, the amount apparently digested can
be calculated by the difference. When, how-
ever, two or more feeds are concerned, the
possibility of interaction between one feed and
another involves a deviation, the extent of which
is still unknown.
*Under the grant of the Imperial Council of Agricul-
tural Research India
In such cases the usual procedure of estima-
tion is by what may be called "the method of
elimination". It dates back since its inception
about 1860 by Henneberg and Stohmann and
is still in almost universal use. It requires one,
two or three successive feeding and metabolic
tests, depending on the number of feeds used.
The first trial is conducted with one feed, and,
when the digestibility of this feed is thus ascer-
tained, the second trial is conducted in which
this feed is given in combination with the