Colostrum

Colostrum is the first form of milk produced by mammalian females after birth. It is a thick, yellowish fluid that is rich in nutrients and immune factors, and it typically accompanies the newborn in the initial days before transitioning to mature milk. In humans, production begins around pregnancy end and is most abundant in the first one to three days; in dairy species, the initial milk is also highly concentrated and is followed by gradual transition to regular milk.

Colostrum has a distinctive composition, with higher protein content and lower lactose than mature milk. It contains elevated levels of immunoglobulins (such as IgA, IgM, and IgG in varying amounts by species), lactoferrin, lysozyme, cytokines, growth factors, and complex oligosaccharides. The immunoglobulin profile varies by species, with cow colostrum often rich in IgG and human colostrum emphasizing secretory IgA.

The principal function of colostrum is to provide passive immune protection to the newborn, supporting gut maturation and barrier function, and helping establish early gut microbiota. Its bioactive components contribute to infection defense and the development of the digestive system, which is especially important for vulnerable neonates, including preterm infants.

In practice, human colostrum is normally consumed via breastfeeding, and donated colostrum may be used when mother's milk is unavailable. In agriculture and some markets, colostrum from dairy animals is collected as a separate product or processed for supplements. Safety considerations include allergies to dairy proteins and, in some cases, regulatory guidance on supplementation and product labeling.