A utilização de procedimento linear-platô para descrever a resposta de um indivíduo a ingestão de um nutriente na população tem sustentação teórica, uma vez que cada indivíduo tem seu máximo potencial de produção determinado geneticamente, e qualquer aumento no consumo de nutriente limitante acima de manutenção resulta numa resposta linear na massa de ovo até atingir o potencial genético e, portanto, atendendo a exigência do indivíduo. No entanto, por causa da distribuição do peso corporal e da massa de ovos na população, a resposta média da população é curvilínea, a qual anula a possibilidade de definir uma "exigência" para o nutriente limitante, e, ao invés disso, leva à possibilidade de definir uma ingestão ótima econômica do nutriente. O Reading Model descreve a resposta da população à ingestão do nutriente limitante, integrando as respostas dos indivíduos que constituem a população. A resposta da população é obtida invertendo um modelo fatorial simples, usando parâmetros para descrever o peso corporal, máximo potencial de produção e as respectivas distribuições (normal) e covariância. Reading Model descreve a resposta da população à ingestão do nutriente limitante, integrando as respostas dos indivíduos que constituem a população. A resposta da população é obtida invertendo um modelo fatorial simples, usando parâmetros para descrever o peso corporal, máximo potencial de produção e as respectivas distribuições (normal) e covariância. A resposta média da população é representada por um modelo linear-platô com uma forma sigmoidal. O Reading Model tem sido amplamente utilizado para estimar a ingestão ótima econômica de aminoácidos para poedeiras comerciais, com diferenças no peso corporal e massa de ovo

The use of a linear-plateau procedure to describe the response of an individual in the population has theoretical support, since the maximum potential performance of each individual is genetically determined, and any increment in intake of the limiting nutrient above maintenance will result in a linear response in output until this genetic potential, and hence requirement, is reached. However, because of the distribution of body weights and maximum potential outputs in the population, the mean response of the population is curvilinear, which negates the possibility of defining a 'requirement' for the limiting nutrient, and instead leads to the possibility of defining an optimum economic intake of the nutrient.. The Reading model describes the response of a flock to a limiting nutrient by integrating the responses of the individuals making up the population. The response of the population is obtained by inverting a simple factorial model using parameters to describe the mean body weight and maximum output of the flock, their distributions (normal) and covariance. The average response of the population is represented by a linear plateau model with a sigmoidal shape. This model has been widely used to predict the optimum economic intake of amino acids for commercial laying flocks varying in body weight and potential egg output

The objective of this paper is to present some of the issues faced by those whose interest is to predict responses in poultry, concentrating mainly on those related to the prediction of voluntary food intake, as this should be the basis of models designed to optimise both performance and feeding programmes. The value of models designed to predict growth or reproductive performance has been improved inestimably by making food intake an output from, as opposed to an input to, such models. Predicting voluntary food intake requires the potential of the bird to be known, be this the growth of body protein or lipid, the growth of feather protein, or the rate at which yolk and albumen may be deposited daily in the form of an egg, and some of the issues relating to the description of potentials are discussed. This potential defines the nutrients that would be required by the bird on the day, which can be converted to a desired food intake by dividing each requirement by the content of that nutrient in the feed. There will be occasions when the bird will be unable to consume what is required, and predicting the magnitude of these constraints on intake and performance provides the greatest challenge for modellers. This paper concentrates on some issues raised in defining the nutrient requirements of an individual, on constraints such as high temperatures and the social and infectious environment on voluntary food intake, on some recent differences in the response to dietary protein that have been observed between the major broiler strains, and on the methodologies used to deal with populations of birds, and finally with broiler breeder hens, whose food intake is constrained by management, not by the environment. These issues suggest that there are still challenges that lie ahead for those wishing to predict responses to nutrients in poultry. It is imperative, however, that the methods used to measure the numbers that make theories work, and that the theories themselves, are robust and unambiguous such that the resultant models can be used to assist the poultry Industry to become more efficient especially when designing feeds and feeding programmes.