ABSTRACTS
Protein standards for milk production. J. MACKINTOSH (1939).
Agric.
Progress 16, 195-201.
T HE paper describes the results obtained in a large-scale experiment on the protein
standards for milk production. The experiment was conducted during the winter
and spring periods of 1935-36 and 1936-37 on farms in the south of England.
The author has drawn attention to the investigations carried out during the past few
years in the United States as well as in some European countries, which have shown that
equally good results could be obtained in practice by the use of ration supplying appre-
ciably lower quantities of protein equivalent than the usually recommended 0.6 lb.
for the production of 10 lb. of milk containing 3.7 per cent of fat. Having this consi-
deration in mind he has studied the effect of two production mixtures, one designed to
comply with the accepted English standard, the other supplying approximately 2/3rd
of this amount. In order to avoid complications arising from the use of different food-
stuffs, the protein mixtures in both ' high ' and ' low ' groups were made up of the same
materials by varying the proportion of the constituents. The maintenance ration was
adjusted as far as possible to comply with the usual standard, viz. 6 lb. of starch equi-
valent and 0.6 lb. of protein equivalent per 1,000 lb. live-weight.
During the first winter some 500 cows and in the second winter some 900 cows were
under experiment. The cows in each farm were grouped in pairs, both animals in each
pair being as similar as possible in breed, age, date of calving, milk-yield, etc. After
pairing, one in each pair was allocated to a different production mixture.
The effect of the high and low protein mixtures showed that the lower protein con-
tent in the production mixture (a) had no detrimental effect on the fatness, handling
properties or appearance of the cows, (b) was equally effective for milk production and
(c) produced milk of almost identical composition.
From the result of the experiment, the author concludes :—
(1) The protein standards for milk production, under the environmental condi-
tions studied, could be lowered by 30 per cent without detriment to the
condition of the cows and the yield or quality of the milk.
(2) When hay is limited and straw is largely used in the maintenance ration, the
reduction of protein standard by 20 per cent is more advisable. [S. K. T.].
On vaccination of calves against infectious abortion.
A. THOMSON
(1939). J. Comp. Path. 52, 192.
A NUMBER of recent American laboratory experiments are detailed to show that it
is possible to protect cattle against infectious abortion by vaccinating them as calves.
This vaccination consists of a single subcutaneous injection of living Brucella abortus
of low virulence. It seems that the idea behind calf-hood vaccination was
that the infection set up by vaccination may pass off in the long period between
vaccination and pregnancy, as no localisation could take place for want of a developed
udder : and yet the calf develops sufficient resistance to a subsequent infection.
The author has tried the utility of calf-hood vaccination under field conditions.
The same strain of low virulence (No. 19) as used in the American experiments was
employed for vaccine production. The vaccine was prepared by suspending well-
developed agar surface cultures in physiological saline solution. It was intended to use a
suspension equal in opacity to 10× tube 1 of McFarland's nephelometer, but actually a
thicker emulsion was used. The vaccine was introduced by the subcutaneous route in
three to ten c.c. doses. The treated calves had fever for a couple of days but had no
other serious disturbances. There was no instance of abscess formation.
Six large farms were available for this experiment. In each farm roughly about two-
thirds of the number of calves were vaccinated, the other one-third being left unvaccinated
as controls. The calves for vaccination and control were picked at random and during
the period of observation they lived together under identical conditions. The age of the
animals ranged from three to eight months but most of them were between four and six
months of age.
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