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THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ I, III
3. The isolation of the species of the organism in question is difficult to accomplish. There
appears to be no certain period during the course of infection in which the organism can be regularly
isolated.
4. The microscopic study of the tissues of 33 birds has shown these definite lesions ; perivascular
foci of hyperplasia in the spleen, perivascular foci in conjunction with the interlobular vessels of the
liver and hydropic degeneration of the parenchymal cells of the liver, cloudy swelling and necrosis
of tubular epithelium of the kidneys and peribronchiolar lesions in the lungs.
Further: The disease has been found to exist in naturally infected flocks. Fourteen birds ob-
tained from two of these flocks reacted to the agglutination test and showed typical microscopic
lesions.
Although the disease is not necessarily fatal, it may be of considerable economic importance due to
the greatly decreased egg yield of the infected birds.
The Mineral Requirements of Dairy Cattle.—J. A. CRICHTON, M.A., The Rowett
Research Institute, Aberdeen. (From the Journal of Dairy Research, Vol. II, No. 1,
December 1930.)
SUMMARY AND CONCLUSIONS.
The most important fact brought out by a review of the present position of our knowledge of
mineral metabolism and the mineral requirements in the dairy cow is, that, in spite of the amount of
work which has been done on the subject, our information is exceedingly scanty. We know that
deficiency of calcium or phosphorus may affect rate of growth, milk yield, breeding capacity, and in
all probability susceptibility to certain diseases. We know also that even on what are counted good
rations, depletion of the tissues, especially of calcium, in heavy milking cows during lactation is
common. In some districts deficiency of iodine causes patholgical conditions, and it is common
knowledge based on practical observations that even on pasture there is liable to be a deficiency of
chlorine. With regard to the possibility of deficiencies of other mineral elements and the effect
of such deficiencies on the health and milk production of cows, we have not yet even begun to
accumulate knowledge. It is thus impossible to make a final pronouncement with regard to any of
the main problems. We need many more data on the metabolism of minerals in the lactating
animal and on feeding experiments of long duration with rations of different mineral content.
Such information as we have, however, suggests that the subject is one of great potential prac-
tical importance, and that if the necessary information were available it might be applied to the
more economical production of milk, both by increasing milk yield and by reducing mortality from
disease.
With regard to the information we do possess, much of it is not immediately applicable in practice
because the data have been accumulated with diets and under conditions which have no parallel
in practice. The following conclusions sum up in a general way the practical bearing of our present
knowledge.
It will be convenient in summing up the position to deal first with calcium and phosphorus, the
two elements required in largest amounts, and the two on which most observations have been made.
In the case of hand-fed calves the meals and other concentrates used to make up milk substitutes
are different in their mineral content from milk, and liable to be deficient in certain elements.
Further, the factors which make for the assimilation of calcium do not occur in ordinary concentrates
to the same extent as in fresh milk. The experimental data, as far as they go, indicate that if the
ration be balanced by the addition of a suitable mineral mixture and some cod-liver oil, the " con-
dition " of the calves is improved and their rate of growth increased.