Adjustment of growth models in broiler chickens

Leandro Félix Demuner,Vinicius Camargo Caetano,Daniel Emygdio De Faria Filho,Cesar Gonçalves De Lima,Julian Andrés Muñoz,Diana Suckeveris,Douglas Emygdio De Faria

doi:10.1590/s0100-204x2017001200013

Leandro Félix Demuner, Vinicius Camargo Caetano + Show 5 more

Open Access

https://doi.org/10.1590/s0100-204x2017001200013

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Abstract

Abstract: The objective of this work was to investigate adjustments of the Gompertz, Logistic, von Bertalanffy, and Richards growth models, in male and female chickens of the Cobb 500, Ross 308, and Hubbard Flex lines. Initially, 1,800 chickens were randomly housed in 36 pens, with six replicates per lineage and sex, fed ad libitum with feed according to gender, and bred until 56 days of age. Average weekly body weight for each line and sex was used to estimate model parameters using the ordinary least squares, weighted by the inverse variance of the body weight and weighted with a first-order autocorrelated error structure. Weighted models and weighted autocorrelated error models showed different parameter values when compared with the unweighted models, modifying the inflection point of the curve and according to the adjusted coefficient of determination, and the standard deviation of the residue and Akaike information criteria exhibited optimal adjustments. Among the models studied, the Richards and the Gompertz models had the best adjustments in all situations, with more realistic parameter estimates. However, the weighted Richards model, with or without ponderation with the autoregressive first order model AR (1), exhibited the best adjustments in females and males, respectively.

Highlights

The current lineages of broiler chickens are a result of successful selection programs to achieve rapid growth, improvements in body conformation, and a consequent reduction in animal slaughter age (Zuidhof, 2014)
Performance of broiler chickens by adjusting growth curves. These curves arise from mathematical models that synthesize the development of the animal, in three or four parameters, evaluating the responses of the treatments over time, identifying the younger and heavier animals in a given population (Freitas, 2005)
Despite the weekly removal of birds, the mean body weight was close to the average recorded in the manuals of the respective lines

Summary

Introduction

The current lineages of broiler chickens are a result of successful selection programs to achieve rapid growth, improvements in body conformation, and a consequent reduction in animal slaughter age (Zuidhof, 2014). Performance of broiler chickens by adjusting growth curves. These curves arise from mathematical models that synthesize the development of the animal, in three or four parameters, evaluating the responses of the treatments over time, identifying the younger and heavier animals in a given population (Freitas, 2005). Modeling in animal production has a fundamental role in helping to maximize the system by producing high-precision estimates. This estimation depends on the non violation of statistical assumptions and can produce imprecise results, especially in cases with few samples (Mazucheli et al, 2011)

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