Colostrum is different from milk as it contains a mixture of both lacteal secretions and proteins found in blood serum. Colostrum production is under hormonal control and is influence by estrogen, progesterone, corticosteroids, growth hormones, and prolactin. During late gestation high levels of estrogen and progesterone initiate colostrum production. At parturition, the spike in corticosteroids and drop in progesterone facilitate the transition to normal milk production. In general, the first six milkings after parturition are considered colostrum due to differences in milk composition.

These differences in milk composition include higher levels of protein, fat, carbohydrates, vitamins and minerals. In addition, high levels of fat and lactose provide the energy necessary for the calf to regulate its own body temperature. This is critical, as research has suggested that without this energy source calves fat stores would only last about 18 hours. Moreover, colostrum represents the first time the newborn calf will obtain nutrients through digestion instead of from the placenta or maternal blood supply. In addition to energy, the high levels of vitamins and minerals in colostrum may be necessary to initiate the calf's metabolism and facilitate the development of its own digestive system. More interestingly, researchers have discovered that colostrum contains high levels of numerous growth hormones which include insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II), epidermal growth factor (EGF), transforming growth factor (TGF), insulin, cortisol, relaxin and thyroxine. Most notably IGF-I and II have been shown to be important for both mammary development and maturation of the digestive system, and may influence the long-term thrift and performance of the animal. Finally, because colostrum is fluid this helps hydrate the neonate and the warmth helps the calf overcome the initial shock of entering the world.

Combined these factors show how high quality colostrum is more than just IgGs and feeding this first meal as soon as possible following parturition can influence the long-term thrift of the animal and improve performance as she transitions into the lactating herd.