Agriculture Reference
In-Depth Information
15
Maintenance Requirements
for Amino Acids in Poultry
M.A. Bonato,
1
N.K. Sakomura,
1
*
J.C.P. Dorigam
1
and R.M. Gous
2
1
Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil;
2
University of KwaZulu-Natal, Pietermaritzburg, South Africa
Abstract
Maintenance may be defined as the state in which the animal can maintain all its vital functions without
any loss or gain in body tissue and without producing any product. Defining the amino acid require-
ments for maintenance by poultry is an area of nutrition that has still not been satisfactorily resolved.
A number of difficulties arise, among which are the difficulty in defining the methodology required to
measure these requirements, and in agreeing upon a general scaling rule that relates the maintenance
requirement to the animal's characteristics and state. Based on these assumptions one methodology was
used to estimate the methionine + cystine (Met+Cys), threonine (Thr), lysine (Lys) and valine (Val) main-
tenance requirements for poultry with several metabolic trials using Cobb
®
and Bovans White
®
roosters.
Measured amounts of a nitrogen-free diet and first-limiting amino acid were fed by intubation each day
for 3 days. A nitrogen-free diet containing energy, vitamins and minerals was made available
ad libitum
during the balance period, to ensure that the birds remained in positive energy balance. The excreta were
collected in trays for 3 days. The nitrogen content of the excreta was determined with dried homogen-
ized samples, as well as diet samples, in order to determine the nitrogen balance (
NB
). Linear regressions
describing the effect of each limiting amino acid intake on nitrogen retention were:
NB
= -
279
(±48.0)
+ 3.20 (±0.20) Met+Cys (
r
2
= 0.82);
NB
= -
191
(±59.7) + 2.53 (±0.20) Thr (
r
2
= 0.60);
NB
= -
304
(±38.5)
+ 3.56 (±0.20) Lys (
r
2
= 0.94);
NB
= -501 (±53.4) + 2.29 (±0.16) Val (
r
2
= 0.89); where the amino acid intake
is in mg/
BP
0.73
day. The Met + Cys, Thr, Lys and Val required to maintain the body at zero nitrogen
retention were estimated to be 87.2, 44.7, 85.2 and
219
mg/
BP
0.73
day, respectively.
Introduction
idea of the conservation status of an animal
that is not performing any work or producing
any product. In addition, nutrient intake and
excretion must be perfectly balanced in order
not to have losses or gains.
Many studies have been carried out
since the 1960s attempting to estimate the
maintenance requirement of each amino
acid for different chicken classes (broilers,
The estimation of the maintenance require-
ments of animals poses particular problems
because maintenance is a concept, and is there-
fore difficult to define and measure. A complete
description of the concept of maintenance was
made by Armsby and Moulton (1925), who
explained that maintenance involves the
