Agriculture Reference
In-Depth Information
21
A Comparison of Two Approaches for
Ratios of Fast-growing Broilers
J.C.P. Dorigam,
1
N.K. Sakomura,
1
* A. Sünder
2
and C. Wecke
2
1
Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil;
2
Georg-August-University Goettingen, Goettingen, Germany
Abstract
Two approaches using the amino acid (AA) dilution method, the comparative slaughter and nitrogen
(N) balance methods, were used in the present study to re-evaluate the assumptions of ideal ratios
between the essential amino acids (EAA): lysine (Lys), methionine + cystine (Met+Cys), threonine
(Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine +
tyrosine (Phe+Tyr), glycine + serine (Gly+Ser) and histidine (His) for growing broilers of the Cobb
500 genotype over three periods (I:
6
to 21 days, II:
22
to 37 days, and III:
38
to 53 days). In each trial
120
male chickens were housed in metabolic cages for assessment of individual N balance and AA
efficiency. An AA-balanced diet (BD) was formulated according to the recommendations of Brazilian
tables for the ideal protein in growing broilers. The diets with different limiting AAs were created
by dilution of the BD with maize starch to achieve 0.70 of the AA level in BD and supplemented
with crystalline AAs, except for the AA under study. The AA-diluted diets led to significant impair-
ment of protein utilization and indicated the valid limiting position of these AAs. Also, at the start
and end of the trial a group of birds with the mean body weight of each replicate was killed with no
blood loss to determine N deposition using the comparative slaughter technique. The mean values
of the optimum ratios of the
11
tested EAAs determined by comparative slaughter in the three
periods are: Lys
100,
Met+Cys
65,
Thr
66,
Trp
17,
Arg
108,
Val
79,
Ile
61,
Leu
122,
Phe+Tyr
128,
Gly+Ser
155
and His
41.
Based on observed AA efficiency data, the optimum ratios determined by
N balance are: Lys
100,
Met+Cys
72,
Thr
65,
Trp
17,
Arg
106,
Val
76,
Ile
67,
Leu
107,
Phe+Tyr
115,
Gly+Ser
137
and His
35.
There are some differences among the results obtained by the two methods
(the broken line model and the Goettingen approach) and they will be discussed in accordance with
the key assumptions.
Introduction
protein can be considered to be the degree to
which the composition of the absorbed AA
mixture satisfies the AA balance required by
the animal (Wang and Fuller, 1989). Conse-
quently the estimation of the essential amino
acids (EAAs) required by an animal can be
In poultry feed formulation the quality of a
dietary protein is associated with its amino
acid (AA) composition and its bioavailabil-
ity. In another words, the quality of a dietary
