D. Carotene - is a precursor of vitamin A, and is a yellow pigment. Guernsey and Jersey cows convert much less carotene to vitamin A than other breeds of dairy cattle. Thus, milk from Guernsey and Jersey cows is yellow. A equivalents am milk from other breeds. Stage of Lactation and Persistency Colostrum vs. Milk See also The Neonate and Colostrum Lesson.
Colostrum is produced by the udder immediately after parturition.
The composition of colostrum is considerably different from the composition of normal milk. Three to 5 days immediately postpartum is needed for the secretions to change to the composition of milk. During this period the total solids, especially the immunoglobulins, are elevated. Newborn calves are practically devoid of immunoglobulins, the antibodies against various disease organisms. Calves must ingest the immunoglobulins from colostrum to acquire a passive immunity against common calfhood diseases.