Submitted to: Australian Poultry Science Symposium
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 10, 1994
Publication Date: N/A
Interpretive Summary: An understanding of the endocrine factors regulating differentiation, growth and metabolism in avian species are needed so that the potential for maximizing hatchability and genetic potential can be realized. The hormonal regulation of growth and metabolism is dynamic and complex. This review has as its focus selected aspects on the role of hormones in regulating cell growth and metabolism in poultry with emphasis on the insulin-like growth factors (IGF-I and -II) and their binding proteins (IGFBPs). It is well-established that the synthesis and release of the IGFs are under the influence of somatotropin or growth hormone. The indirect effects of growth hormone are mediated via IGF and include increased amino acid uptake and protein synthesis, cell differentiation and proliferation. This review summarizes our understanding of the IGFs in poultry, and how this may impact metabolic events and potential use of these hormones to enhance poultry production.
Before biotechnology can be applied to improve production efficiency of poultry, a detailed knowledge of the genetic control of growth and the physiology and biochemistry of the regulatory factors must be clearly understood. This is best illustrated by the failure of simple and direct approaches, such as the injection of chicken ST, to have significant commercially relevant effects. Similarly, limited studies to date have failed to demonstrate that the administration of exogenous insulin-like growth factors (IGFs) will influence poultry growth and metabolism in a significant manner. Any affect that the IGFs may have on growth can not be entirely attributed to increased circulating or tissue IGF-I concentrations. Changes in insulin-like growth factor binding protein (IGFBP) physiology must also be considered as well as species specificity. It may be for example, that for exogenous IGF to be effective in positively influencing body growth and carcass composition in domesticated birds, co-administration of chicken IGFs and IGFBPs may be required. With the cloning and expression of the IGFs and the production of mass quantities of these hormones, the question of biological effects and usefulness of enhanced IGF status in poultry becomes critical.