Colostrum and passive transfer

A calf is born with almost no circulating antibodies and depends on colostrum for them. The gut can absorb antibodies intact only for roughly the first day of life, and absorption is already declining within hours of birth.

Good practice is a first feeding of three to four litres of clean, good-quality colostrum as soon as possible after birth. Failure of passive transfer is conventionally defined as serum IgG below 10 g/L when measured at one to two days of age.

Written for the 2026 edition of the library.