Regulation of development by nutrition and by the somatotrophic and thyroid axes in the neonatal pig

The neonatal period is a particularly critical stage during which the long- term development of the individual can be affected. The rapid somatic growt h is accompanied by tremendous anatomical, physiological and chemical compo sition changes. This period is also associated with dramatic changes in the endocrine system which plays a central role in the control of metabolism a nd growth. The review focuses primarily on the somatotrophic and thyroid ax es. Changes in hormone and binding protein concentrations in plasma, as wel l as receptor expression in target tissues, are considered. After birth, th e ability of the neonate to express its growth potential is related to milk intake and milk quality. There are interactions between nutrition, endocri ne parameters and development. Tn addition to nutrients, colostrum and milk contain a large group of biologically active components such as enzymes, h ormones, growth factors and immunological agents that may be involved in th e neonatal development. The possible role of milli-borne insulin-like growt h factor-I (IGF-I) on body growth, the gastrointestinal tract and protein s ynthesis in neonates has been the subject of considerable investigation in the past ten years. There is increasing evidence that milk-borne IGF-I sign ificantly affects gastrointestinal growth and development. The effects of t his factor on development of other tissues and/organs are not so clear. (C) 2000 Elsevier Science B.V. All rights reserved.