Agriculture Reference
In-Depth Information
18
Description of the Growth of Body
Components of Broilers and Laying Pullets
E.P. Silva,
1
N.K. Sakomura,
1
* S.M. Marcato
2
and R. Neme
3
1
Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil
;
2
Universidade Estadual de Maringá, Maringá, Paraná, Brazil
;
3
Ilender
Pharmaceutical Corporation, Campinas, São Paulo, Brazil
Abstract
This review presents a description of the growth of broiler and laying chicken strains studied at the
Laboratory of Poultry Science, Universidade Estadual Paulista (UNESP)-Jaboticabal. Two commercial
broiler strains and four laying strains were assessed. Ross 308
®
and Cobb 500
®
broilers were reared to
56 days of age using 1920 broiler chicks divided into four groups (two strains × two sexes), each with four
replicates of
120
birds, resulting in
16
experimental units. The four laying strains studied, to 126 days of
age, were Hy-Line Brown, Hisex Brown, Hy-Line White W-
36
and Hisex White. Three hundred chicks of
each strain, all females, were separated into groups to create four replicates of
75
birds, resulting in
16
experimental units. Every week, the birds were weighed and a sample was selected for carcass analysis
based on the average weight of the experimental unit. Measurements were made of their chemical com-
ponents (water, protein, lipid and ash) from which the growth of each component was described using
the Gompertz function. Allometric coefficients were determined for the chemical components of the
body in relation to the feather-free protein weight of the body. Differences between the broiler and laying
strains were observed in some parameters of the Gompertz function. Among the broiler strains, differ-
ences were observed in the protein content of the body and in the weight of the feathers. Differences
between laying strains were in protein weight and rate of maturing. The allometric coefficients revealed
little difference between the genotypes, in both broiler and laying strains, indicating that it is possible to
use generalized parameters to describe the growth of chemical components of the body using allometry.
The different rates of growth between genotypes indicate that the intakes of energy and amino acids
required to enable them to reach their genetic potential would differ between genotypes.
Introduction
authors separates the requirements for main-
tenance and weight gain, which introduces
the need to predict the growth of the animal
because many modifications can occur in
the physical and chemical composition of the
bird from birth to maturity (Emmans, 1981).
Therefore, applying a mathematical descrip-
tion of growth assists in describing the
changes in body composition as the animal
Body composition was suggested as a means
of estimating the amino acid requirements of
poultry in the 1950s (Williams
et al
., 1954),
and later it was applied in a factorial model
to predict the protein and amino acid require-
ments of poultry (Hurwitz and Bornstein,
1973). The factorial model described by these
