Colostrumphase

Colostrum phase refers to the initial period of lactation immediately after birth when the mammary glands produce colostrum, the first form of milk. This phase follows parturition and precedes the emergence of mature milk. In humans, colostrum phase typically lasts about two to five days, though the exact duration can vary among individuals and across species.

Colostrum is distinguished by its unique composition. It is rich in immunoglobulins, especially IgA, and contains higher concentrations of proteins, lactoferrin, leukocytes, growth factors, and cytokines compared to mature milk. It is relatively low in lactose and fat, which contributes to a thicker, more concentrated fluid. The combination of immune and growth factors supports the newborn's developing immune system and gut barrier.

The primary function of the colostrum phase is to provide passive immunity and to prime the neonate’s digestive system. The antibodies help protect against pathogens in the early environment, while growth factors and other bioactive components support intestinal maturation and microbiome establishment. As lactation progresses, the mammary gland gradually shifts to producing mature milk, with increasing lactose and fat that provide energy and nourishment for growing offspring.

Variation exists across species in the duration and composition of the colostrum phase. In agricultural settings, timely colostrum feeding is emphasized to optimize neonatal immunity, whereas in humans, early breastfeeding or colostrum supplementation may influence early immune development.