Early nutrition as a tool to improve the productive performance of broiler chickens

The final phase of embryonic development and the immediate period after hatching are pivotal moments in the life of broiler chickens. The lack of food for newly hatched chicks leads to decreased body weight. Under commercial conditions, the hatched eggs placed on the same hatching shelves are usually hatched within a period of 24-36 hours, which results in the early hatched chicks falling under harsh conditions of prolonged fasting period, and other periods are added to this period including determining sex, sorting, vaccination, and transporting to the farm, these factors directly contribute to the delay in growth. In addition, this period is very important, as the body weight increases during the first week 3-4 times, and the accompanying clear development in the digestive system, a negative impact on the immune ability of hatched chicks was observed as a consequence of the delay in obtaining food and thus become more sensitive to disease and thus the increase in mortality rates. To maximize the use of nutrients and the growth of chicks, early growth and development of the gastrointestinal tract (GIT) are crucial. It is possible to increase the rates of body growth and improve the gut development rate and thus increase the chicken's productive performance by conducting some strategies during the early stages of age, such as feeding the embryo by injecting eggs with nutrients or directly after the hatch, feeding newly hatched chicks immediately after pipping the eggs results in improved growth, increased the efficiency and development of digestive functions. This review discusses the early nutrition of various nutrients and their impacts on gut health, histomorphology, microbiology, and immunology. Additionally, it will shed light on the future vision of early nutrition as a strategy to modify gut health, promoting broiler chicks' health status and production.