Colostrum contains a high percentage of IgG, especially bovine colostrum. Fat concentration in bovine colostrum is extremely variable. The somatic cell count in the milk also increases after calving when colostrum is produced. Colostrum present in mothers milk is an example of passive immunity. In normal situations, lambs nurse after standing, receiving vital colostrum milk. The early milk from mammals is called colostrum. In general, protein concentration in colostrum is substantially higher than in milk. Colostrum will gradually change to become mature milk. During the late stages of pregnancy, the milk changes to colostrum. Instead, transfer factors derived from cow colostrum and/or chicken eggs yolks are used predominantly today. Colostrum, vital for foal development, was considered unhealthy and withheld from newborns. Colostrum is crucial for newborn farm animals. The colostrum is collected within 24 hours of the cow giving birth. The makeup of the colostrum and the period of secretion varies from species to species. A baby not nursed by the mother was deprived of the laxative colostrum.