Evaluation of the parameters needed to describe the overall growth, the chemical growth, and the growth of feathers and breast muscles of broilers

Abstract

An experiment was carried out to collect data suitable for testing methods used to describe the potential growth and body composition curves of broilers. Males and females of two commercial broiler strain-crosses were grown to 16 wk of age with birds taken at 0, 2, 4, 6, 8, 12, and 16 wk of age for chemical analysis and for the measurement of feather weight and breast meat (Pectoralis major and Pectoralis minor) weight at these ages. The data were used to test the Gompertz growth equation and the assumption of chemical allometry, as well as to estimate the values of the growth parameters for the different genotypes. Feeding and environmental conditions were intended to be such that potential growth and body composition could be attained. The weights of the chemical components for each of the four genotypes were described in terms of the mature weight of these components, their rates of maturing, and the time taken to reach the maximum rate of growth of each component. Allometric relationships between the weights of the chemical components and that of body protein were estimated. The ratio of ash to protein was essentially constant. Water matured more slowly, and lipid faster, than protein. For males, and for females up to 8 wk, the models were satisfactory. For females after this age, lipid growth was faster than expected from the earlier period, probably in preparation for egg production. There were small, but important, differences in the values of some parameters between the strain-crosses. For each of the four genotypes the changes in weight of feathers and breast meat with time were described in terms of the Gompertz growth function, which described the data very well. The parameters of the function for each component and genotype-mature weight, rate of maturing, and the time taken to reach the maximum rate of growth B were evaluated. For the feathers, the value of the rate parameter was higher than that estimated for the body as a whole. For the two breast muscles, and for their total weight, the value of the rate parameter was similar to that for the body as a whole. There was a simple allometric relationship between the weights of the breast muscles and that of the whole body. As a consequence, the development of the yield of breast meat for a given genotype could be described by the values of the two parameters: mature yield and the allometric exponent. A description of each genotype of interest is seen as an essential first step in using a simulation model either to predict requirements, or to predict the effects of different feeding programs, and environmental conditions, on the performance of broilers.

Breeding for efficiency in the broiler chicken: A review

“…2 was used to calculate the energy retention for the extremes of body composition reported in the literature. In order to estimate the body compositions, the ratios of ash to protein and water to protein were assumed to be constant (0.2 and 3.4 kg kg −1 , respectively) (Gous et al 1999). The leanest body composition the birds could achieve in the scenarios had 20.2 % protein and 7.9 % lipid based on the data presented by Mussini (2012); the fattest had 16.1 % protein and 26.9 % lipid based on the data presented by Fleming et al (2007).…”

Methodologies for modelling energy and amino acid responses in poultry

“…The growth curves obtained in this way allow comparisons to be made between breeds and strains. Examples of such investigations are in Hancock et al (1995), and Gous et al (1999).…”

Consequences of genetic change in farm animals on food intake and feeding behaviour

“…An attraction of the function is this simplicity of its having just two parameters. The components of interest may be either the major chemical components of the body (protein, ash, water and lipid) or organ or tissue groups (Emmans, 1989;Gous et al 1999). The growth rates of the chemical components is of particular interest here, as these are needed to predict requirements (Emmans & Fisher, 1986).…”