Agriculture Reference
In-Depth Information
20
Amino Acid Requirements for Pullets
Based on Potential Protein Deposition and
the Efficiency of Amino Acid Utilization
M.A. Bonato,
1
N.K. Sakomura,
1
* E.P. Silva,
1
J.A. Araújo,
1
A. Sünder
2
and F. Liebert
2
1
Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil;
2
Georg-August-University, Goettingen, Germany
Abstract
The aim of this study was to estimate lysine (Lys), methionine (Met) and threonine (Thr) requirements for
pullets based on protein deposition and efficiency of amino acid dietary, based on the Goettingen University
approach. Three assays of nitrogen balance were conducted with White Dekalb pullets, in periods I (
14
to
28 days), II (
56
to 70 days) and III (
96
to 112 days). In each experiment,
56
pullets were distributed in a
completely randomized design, with five treatments and six replications. The treatments were five diets
with different nitrogen levels keeping constant the ideal ratio (amino acid/Lys), except for the amino acid
being tested. Each trial included a control treatment in which a small amount of the amino acid under in-
vestigation was added to a diet with the same composition as the diet with the lowest content of the test
amino acid to verify that the amino acid under test was first limiting in each trial. The data for nitrogen
intake (
NI
) and nitrogen excretion (
NEX
) were collected and fitted by an exponential equation for each
period to determine the nitrogen maintenance requirement (
NMR
). The maximum theoretical potential for
nitrogen retention (
NR
max
T
) was determined by the exponential relation between
NI
and nitrogen deposited
(
ND
) for each period. Based on diets limiting in Lys, Met and Thr, the efficiency (
bc
-1
) was obtained. The
quality of dietary protein (
b
) is dependent on concentration of the limiting amino acid in the protein of the
diet (
c
). Intake limiting amino acid (
LAAI
) was calculated. All fitted equations were significant (
P
< 0.01).
The
NMR
values determined were
270
mg/kg
0.67
/day,
303
mg/kg
0.67
/day and 348 mg/kg
0.67
/day, and the
NR
max
T
values were 3208 mg/kg
0.67
/day, 2353 mg/kg
0.67
/day and 1739 mg/kg
0.67
/day for each period. The
bc
-
1
values were:
50,
90
and
100
for Lys;
170,
230
and 350 for Met; and
100,
160
and
180
for Thr, for periods I, II
and III, respectively. These parameters were used in the formula and
LAAI
was determined considering
40%, 50% and 60% of
NR
max
T
for the periods I, II and III, respectively. In general, based on 50% of the
NR
max
T
values the requirements are lower than recommended in the literature, which is due to the methodology
applied in this study (factorial model, type of approach), although the requirements are consistent for pullets.
Introduction
2011). The egg is the main product of laying
hens in commercial enterprises and contrib-
utes to the food protein supply. To ensure
optimal development of layers (including
Poultry is one of the most important providers
of animal protein to human diets (EMBRAPA,
