The transition from passive to active immunity of the calf
Straub, O.C.
Deutsche Tierärztliche Wochenschrift 79(24): 613-615
1972
ISSN/ISBN: 0341-6593 PMID: 4567876 Document Number: 53770
The passive immunity acquired by the calf through the colostrum progressively declines until the calf is left unprotected. Then the calf is capable of immunological response when challenged by a virus, and may exhibit clinical symptoms of disease. During the period of gradual fading of immunity, animals may act as disease carriers and excretors of virus, though not themselves clinically ill. Passively protected calves should not be vaccinated until 3 or 4 months old. New animals in feedlots should be protected on arrival by vaccination or by serum or citrated blood from immune animals. All animals should be vaccinated at 4-5 months of age.