Endocrine Control of Postnatal Growth in Poultry

Abstract

This paper provides an overview on the role of several endocrine factors in the regulation of the somatic growth (skeletal muscle and bone development) and body composition in meat-type poultry. The hormones of both the somatotrophic axis (GH and IGFs) and the thyrotrophic (T₄, T₃) axis are a prerequisite for normal growth and development. Posthatch hormone therapy does however not stimulate growth but rather to the contrary. In ovo treatment with somatotrophic hormones seems to elicit positive responses in postnatal growth and adiposity. Androgens are anabolic and their plasma levels are positively correlated with growth rate, whereas estrogens are clearly lipogenic. The androgen : estrogen activity ratio may certainly not be underestimated in growth and adiposity regulation, even in juvenile poultry. Leptin has appetite-reducing properties in chickens and hepatic leptin expression is controlled by several hormones. Finally, feed restriction as well as diet composition is used as models to illustrate how endocrine factors interact with the intermediary metabolism in a deterministic and mechanistic way.