46
ABSTRACTS
[Vol. XXVI, Part I,
Field study of the epidemiology and clinical manifestations of parasitic bron-
chitis in adult cattle. J. F. MICHEL and A. SHAND (1955). Vet. Rec., 67, (14)
T HE authors describe and discuss 17 cases of outbreaks of husk in adult cattle
and their histories, selected from a large number to illustrate the great diver-
sity encountered. In the great majority of outbreaks the infection is said to be
endemic on the farm, generally in a sub-clinical form. The various outbreaks have
no simple factor in common. Whether any external factor renders the adult animals
susceptible to infection does not emerge from this investigation, but inadequate
nutrition also does not appear to be such a predisposing factor. Gradual exposure
to infection is less dangerous than sudden exposure. The longer the animals remain
unexposed to infection the more susceptible they become. The ultimate source of
infection is the small number of larvae disseminated in the faeces of carrier animals
and not those which persist on the ground through the winter. The indications are
that the larvae do not persist on the ground even as long as five months. The
small number of larvae disseminated by carrier animals may turn into a source of
dangerous level of infestation on the ground in two ways : (i) by intervention of
calves who become lightly infected but pass sufficient larvae in the faeces to raise
the level of infestation of the pasture and (ii) directly, where the conditions are
particularly favourable for the larvae. Lush ley pastures appear to represent a
particularly favourable vehicle for the survival and transmission of the infection.
The level of infection on the ground may remain dangerous even after an intervening
hay cut has been taken.
The symptoms appear 12 days or more after exposure to heavy infection or 12
days or less after a move to after-math, or even without any obvious precipitating
cause. The nature of symptoms of husk varies according to their severity. The
most severely affected animals may either get cough or their sudden acute illness
or even death may be the first sign of an impending out-break. The less severely
affected animals often develop symptoms later and then only cough. A continuous
range of symptoms of increasing severity from an occasional mild cough to acute
respiratory distress with pulmonary oedema and emphysema closely resembles the
condition known as fog fever. This fog fever syndrome, when associated with para-
sitic bronchitis, is most frequently seen in adults but may be found in young stock
also. On its appearance the animal presents a pricture of extreme distress, and
conveys the impression that death might supervene at any moment from oxygen
starvation. The other clinical manifestations are : cessation of feeding and drinking,
depression in milk yield, abortion in the later stages of pregnancy and loss of weight
and condition. Complete recovery is possible within three weeks but severely
affected animals may remain desperately ill for months. (S. R. G. M.)
A study of the protein requirements of fattening feeder lambs. L. F. BUSH,
J. P. WILLIAMS and P. B. MORRISON (1955). J. Anim. Sci. 14, 465-469
T WO hundred and ninety-seven feeder lambs were used in three experiments,
spread over three years. Three levels of protein, viz. 10.0 per cent, 11.0 per cent
and 11.8 per cent on the total ration basis were used every year. In addition, the
effect of supplementation with various proportions of alfalfa hay to corn silage, the