SYSTEMS TO PREDICT THE ENERGY AND PROTEIN-REQUIREMENTS OF LAYING FOWL

There are several empirical formulae that describe input and output re lationships in egg production, but their applicability is restricted t o specific genetic, nutritional and environmental conditions. Simplist ic regression relationships are not an adequate basis for the optimiza tion of complex, dynamic and highly interactive production systems. Me chanistic and dynamic models that describe causes and interactions bet ween input and output relations are required. in order to evaluate nut ritional requirements and to predict bird responses to the concomitant influences of the internal and external factors, the development of s uch models seems currently to be the most profound challenge in poultr y science. This paper reviews current empirical systems for predicting nutrient requirements for egg production and discusses the advantages of incorporating mechanistic and dynamic elements.