A sinusoidal equation as an alternative to classical growth functions to describe growth profiles in turkeys

Because of the relatively long growing cycle and the high cost of research into turkey production and nutrition, the potential benefits from modelling growth in this avian species are considerable. Though there are many studies aimed at evaluating animal growth models, the number of studies targeting growth models in turkeys is quite limited. In this paper we present a sinusoidal function to describe the evolution of growth in turkeys as a function of time based on data published by Aviagen. The new function was evaluated with regard to its ability to describe the relationship between body weight and age in turkeys and was compared to four standard growth functions: the Gompertz, logistic, Lopez, and Richards. The results of this study show that the new sinusoidal function precisely describes the growth dynamics of turkeys. Fitting the functions to different data profiles nearly always led to the same or less maximized log-likelihood values for the sinusoidal equation, indicating its suitability in describing growth data from turkeys.(AU)

A sinusoidal equation as an alternative to classical growth functions to describe growth profiles in turkeys

Because of the relatively long growing cycle and the high cost of research into turkey production and nutrition, the potential benefits from modelling growth in this avian species are considerable. Though there are many studies aimed at evaluating animal growth models, the number of studies targeting growth models in turkeys is quite limited. In this paper we present a sinusoidal function to describe the evolution of growth in turkeys as a function of time based on data published by Aviagen. The new function was evaluated with regard to its ability to describe the relationship between body weight and age in turkeys and was compared to four standard growth functions: the Gompertz, logistic, Lopez, and Richards. The results of this study show that the new sinusoidal function precisely describes the growth dynamics of turkeys. Fitting the functions to different data profiles nearly always led to the same or less maximized log-likelihood values for the sinusoidal equation, indicating its suitability in describing growth data from turkeys.

Crescimento em diâmetro do Pinus elliottii e Pinus taeda em áreas arenizadas e degradadas no oeste do Rio Grande do Sul / Diameter growth of Pinus elliottii and Pinus taeda in arenizated and degraded areas in the western of Rio Grande do Sul State, Brazil

Este trabalho foi realizado com o objetivo de estudar o desempenho do Pinus elliottii Engelm. e Pinus taeda L. em áreas arenizadas e degradadas por ação antrópica, na região da fronteira oeste do estado do Rio Grande do Sul. Em povoamentos, foram selecionadas árvores médias, que foram abatidas e seccionadas pelo método de Smalian, a fim de obter discos de madeira para a análise dendrocronológica, para a obtenção do diâmetro por idade. O crescimento em diâmetro, quando comparado entre espécies, apresentou tendências diferentes de níveis de desenvolvimento no tempo. O uso de variáveis dummy no modelo de crescimento permitiu definir uma equação única para estimar o diâmetro em função da idade para ambas as espécies, considerando os níveis de degradação do solo médio e baixo, como variáveis necessárias para estimar o crescimento destas espécies nestes tipos de solos arenizados e degradados.(AU)

This research aims to study the performance of Pinus elliottii Engelm. and Pinus taeda L. in the arenizated and degraded areas by antropic action in the western of Rio Grande do Sul state. In stands were selected medium trees, which were harvested and sectioned by Smalian method to obtain wood discs for dendro chronological analysis to determine the diameter by age. The diameter growth compared between species showed different levels of development over time. The use of dummy variables in the growth model enables a single equation to estimate the diameter as a function of age for both species, considering the medium and low levels of soil degradation, as variables necessary to estimate the growth of these species in these types of arenizated degraded soils.(AU)