Abstract:
1. In a study of the transmission of anti-bodies from immunized pregnant
cows to the colostrum and to their progeny it was noticed that the agglutinin
titre of the colostral whey and of the calf's serum might be several times that
of the dam. At the time of birth hardly any agglutinins, or no agglutinins at all,
could be detected in the calf's serum, but the titre suddenly rose to this high
level within 24 hours after the first suckle. The calf's titre remained high for
two weeks or more, and then gradually declined; but it remained at a significant
level for about three months.
2. When newly-born calves from immunized or unimmunized mothers were
fed on hyperimmune serum before the first suckle large amounts of agglutinins
could be detected in their sera twelve hours later. These agglutinins persisted,
though in progressively decreasing titre, for at least three months.
3. When the calves from immunized cows were inoculated with S. dublin
vaccine one, two or three weeks after a colostral feed, no rise could be effected
in the agglutinin titre and no difference could be detected in the titre whether the
calves had been inoculated or not. The immunity was apparently completely
blocked by the anti-bodies absorbed from the colostrum.
4. When the colostral immunity was challenged with virulent milk cultures
given by the mouth the calves exhibited a fair degree of resistance, and it was
extremely difficult to produce typical symptoms of paratyphoid in them. It is
believed that this immunity is sufficient to protect young calves against natural
exposure to paratyphoid. The immunization of pregnant cows as a means of
protecting new-born calves against paratyphoid is, therefore, recommended as
an additional method of combating the disease. But as hyperimmune sera, when
given before the first suckle, can also transmit anti-bodies to new-born calves
the use of immune sera is advised in cases where immune colostrum is not
available.
