Breastfeeding that is needed for a baby's growth and development. Breastfeeding triggers biochemical reactions which allows for the enzymes, hormones, growth factors and immunologic substances to effectively defend against infectious diseases for the infant. The breast milk also has long-chain polyunsaturated fatty acids which help with normal retinal and neural development. The composition of breast milk changes depending on how long the baby nurses at each session, as well as on the child's age. The first type, produced during the first days after childbirth, is called "colostrum". Colostrum is easy to digest although it is more concentrated than mature milk. It
Colostrum factors through multiple pathways including nutritional support, immunological intervention (through its immunoglobulin and other anti-microbial factors) and growth/healing factor constituents. As pointed out by Kelly, inconsistency between results in some published studies may be due in part to variation in dose given and to the timing of the colostrum collection being tested (first milking versus pooled colostrum collected up to day 5 following calving). Some athletes have used colostrum in an attempt to improve their performance, decrease recovery time, and prevent sickness during peak performance levels. Supplementation with bovine colostrum, 20 grams per day (g/d), in combination with exercise training