Agriculture Reference
In-Depth Information
to Amino Acid Intake
H.C.P. Bendezu,
1
* N.K. Sakomura,
1
K.S. Venturini,
1
J. Sato,
1
L. Hauschild,
1
E.B. Malheiros
1
and R.M. Gous
2
1
Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil;
2
University of KwaZulu-Natal, Pietermaritzburg, South Africa
Abstract
This study was designed to measure the responses of Dekalb laying hens to three amino acids such that
the optimum economic amino acid intakes of these hens could be determined, taking into account vari-
ation in body weight and potential egg output in the population as well as changes in egg revenue and feed
price. Three experiments were conducted with Dekalb White laying hens during the period from
33
to
48
weeks of age, with each trial being divided into four periods of 28 days. Responses were measured to
intakes of lysine, methionine + cysteine and threonine. The laying hens were distributed in a completely
randomized design among eight treatments and six replicates. The treatments consisted of increasing
levels of each of the amino acids under test to obtain a response curve. These levels were obtained using
a dilution technique, and a control treatment was included to confirm that responses were due to the test
amino acid. Egg production (%), feed intake (g), body weight (kg), egg output (g/day) and egg weight (g)
were measured. The control treatment confirmed that the amino acid under test was limiting in each
assay. The Reading model was fitted to the data in each trial using the relevant amino acid intakes and egg
outputs. The coefficients of response obtained were 8.58 mg/g, 7.96 mg/g and 6.73 mg/g egg output, and
36.6 mg/kg, 50.8 mg/kg and 37.2 mg/kg body weight for lysine, methionine + cysteine and threonine, re-
spectively. Assuming a maximum egg output of
55
± 12.5 g/day, an average body weight of 1.45 ± 0.2 kg
and a cost ratio of the amino acid (c/mg) and egg (c/g) of 0.0023 (lysine), 0.0025 (methionine + cysteine)
and 0.0034 (threonine), the optimum economic intakes of each amino acid under current Brazilian condi-
tions were 746, 717 and 593 mg/bird/day for the three amino acids, respectively.
Introduction
Synthetic amino acids such as methionine
(Met), lysine (Lys) and threonine (Thr) are com-
monly used in the poultry industry because they
are limiting in diets based on maize and soybean
meal and because they are now readily available
at a competitive cost. Their inclusion repre-
sents 7% of the cost of the feed (MDIC, 2012).
Responses to amino acids have been
studied extensively because of their nutritional
Feed represents more than 70% of the cost of
production of eggs. In this context, protein is
one of the most costly nutrients and therefore
there is benefit in reducing any excess protein
in the feed by making use of synthetic amino
acids wherever feasible to reduce both the ex-
cess waste of nitrogen and the production cost.
