ABSTRACTS
301
the Agricultural Research Council of the
United Kingdom. Imperial Bureau of Animal
Health, May 1944, Review Series No. 2
THIS report deals with the researches that were
carried out in 20 dairy herds consisting of various
breeds of cows, in five different centres extending
from Ayrshire to Kent over a period of 21 months.
The important cause of bovine mastitis which reduces
the milk yield of dairy herds is Streptococcus agalactiae
though other streptococci, staphylococci and diph-
theroid bacilli cause mastitis in cattle. Mastitis due
to staphylococci is more frequent and important
than was once supposed. The observations described
in this report indicate clearly the routes by which
infection occurs and the cause of persistent herd
infection.
The methods of collection, sampling and examina-
tion of both milk and teat swabs that were adopted
as a standard throughout the investigation have
been described in detail. These examinations have
shown that Sir. agalactiae is a common inhabitant of
the bovine udder or teat canal, even in the absence
of clinical symptoms. Various workers have recorded
the incidence of mastitis due to Str. agalactiae.
Minett reported its isolation from milk of 38.3 per
cent of cows the infection varying from 10 per cent
to 71 per cent in different herds. But there is no
recorded information regarding the occurrence of
this organism on the exterior of the teat. In this
investigation of 16,482 samples of milk examined
Str. agalactiae was isolated from 38.8 per cent. The
results of examination of milk and teat swabs of
different herds are given in tabular form. It was
noticed that some cows which gave consistently
positive milk tests gave very irregular results from
teat swabs, while in others, where milk tests were
negative, positive teat-swab tests were obtained.
The relation between positive milk samples and
positive teat swabs are given. Of the 2177 positive
milk samples 816 or 37.5 per cent were positive for
teat swabs. On the other hand of the 3599 negative
milk samples only 526 or 14.6 per cent were positive
for teat swabs. But of the total positive teat swabs,
61.5 per cent were associated with positive milk
samples. It was proved that the successive positive
teat swabs may not be due to true skin infection but
to repeated contamination by milkers' hands.
Sores, cracks and other blemishes on the teats become
infected very frequently with Str. agalactiae. It was
also noted that heavy skin infection may also occur
in the absence of any lesions on the teats. It was
also proved that Str. agalactiae infection often
persists in the dry udder and also on the teats during
the dry period. The persistent infection in dry cow
is a factor in the maintenance of infection in the
herd.
A search for Str. agalactiae in sites other than the
cow's udder was made with the following findings:
1. The occurrence of Str. agalactiae on the teats of
heifers that have not been milked is extemely rare.
But Str. agalactiae frequently appears in the milk of
first-calf heifers during their initial lactation.
2. Str. agalactiae could not be isolated from the
throat and nostrils of calves or from the vagina of
cows. Some workers, have claimed isolation of
this organism from the mouths of calves suckling
infected cows about eight hours after suckling.
3. Str. agalactiae can be isolated from the great
majority of the hands of milkers who are daily
handling the teats of the cattle in any average herd.
4. Str. agalactiae is not a natural human parasite.
When found on the milkers' hands or in the throat,
this is simply the result of contamination from milk.
5. Sir. agalactiae has been isolated from churn
handles, lids, door, knobs, broom handles and from
the cups of milking machines.
6. The air of cattle sheds is contaminated with
Str. agalactiae, but air-borne infection is of minor
importance as compared with contact infection.
A study of the relation between Str. agalactiae in
milk and clinical symptoms indicated that 283 or
14.3 per cent of 1,977 samples of milk yielding Str.
agalactiae were associated with signs of clinical
mastitis, while only 129, or 3.7 per cent of 3,460
samples of milk not yielding Str. agalactiae were
associated with signs of clinical mastitis. In other
words, signs of clinical mastitis were approximately
four times as frequent when Str. agalatiae was present
in the milk as when it was absent.
Methods of control are detection of infected cases,
eliminating them from the herd, or isolating and
milking the infected cows last. [M.K.S.]
The effect of feeding cottonseed meal as the only
concentrate on several properties of milk.
1. Fat, total solids and ash content. P. G.
MILLER and G. H. WISE (1944). J. Dairy Sci. 27,
275-279
THE object of the experiment was to determine the
effect of feeding cottonseed meal as the only con-
centrate on several properties of milk to a group of
Holstein herd. This was compared with a control
group of an equal number of similar animals which
was fed on a concentrate mixture consisting of four
parts of corn gluten meal, two of wheat bran, two of
ground corn and two of ground oats. The roughage
allowed to both the groups was the same and com-
prised either corn or soybean silage or pasture. In
addition, both the groups were given an allowance of
2 per cent bone meal and 1 per cent salt. The
experimental observation extended to a period of
16 consecutive months.
The data presented showed that four months after
the animals were placed on their respective feed, the
milk yielded by the experimental group had com-
paratively a lower percentage of total solids, fat and