Dirk Hoehler, A. Lemme, V. Ravindran, W.

L. Bryden and H. S. Rostagno. 2006. Feed Fo

rmulation in Broiler Chickens Based on Stan

dardized

Ileal Amino Acid Digestibility. En: Editores:

L. Elizabeth Cruz Suárez, Denis Ricque Marie, Mireya Tapia Salazar, Martha G. Nie

to López,

David A. Villarreal Cavazos, Ana C. Puello Cruz y Armando García

Ortega. Avances en Nutrición Acuícola VIII .VIII Simposium Int

ernacional

de Nutrición Acuícola. 15-17

Noviembre. Universidad Autónoma de Nuev

o León, Monterrey, Nuevo León, México.

ISBN 970-694-333-5.

197

Feed Formulation in Broiler Chicke

ns Based on Standardized Ileal

Amino Acid Digestibility

Dirk Hoehler

1

, A. Lemme

2

, V. Ravindran

3

, W. L. Bryden

4

and H. S. Rostagno

5

Degussa Corporation, Feed Additives

1

1701 Barrett Lakes Blvd., Suite 340

Kennesaw, GA 30144, USA

Phone: 678-797-4326

Fax: 678-797-4313

E-mail: dirk.hoehler@degussa.com

Homepage: http://www.aminoacidsandmore.com

Degussa AG, Feed Additives

2

63457 Hanau, Germany

Institute of Food, Nutrition and Human Health

3

Massey University, Palmerston North

New Zealand

School of Animal Studies, University of Queensland

4

Gatton QLD 4343, Australia

Departamento de Zootecnia

5

Federal University of Vicosa

Vicosa, Brazil

Summary

Analysis of ileal contents rather than excreta is a mo

re reliable method for assessing amino acid digestibility in

poultry. Debate will continue among nutritionists about the re

lative merits of apparent a

nd true digestible amino acid

systems. However, there is no doubt that all digestible amino systems are superior to the use of total amino acids in

feed formulations. Present methods

of evaluating amino acid availability

have specific applications and

shortcomings. Standardized ileal digestibility is discusse

d as the concept of choice and some areas for future

research are highlighted. Performance data in growing broiler chicks demonstrate the advantages of feed formulation

based on standardized ileal digestibility

of amino acids in feed ingredients.

Dirk Hoehler, A. Lemme, V. Ravindran, W.

L. Bryden and H. S. Rostagno. 2006. Feed Fo

rmulation in Broiler Chickens Based on Stan

dardized

Ileal Amino Acid Digestibility. En: Editores:

L. Elizabeth Cruz Suárez, Denis Ricque Marie, Mireya Tapia Salazar, Martha G. Nie

to López,

David A. Villarreal Cavazos, Ana C. Puello Cruz y Armando García

Ortega. Avances en Nutrición Acuícola VIII .VIII Simposium Int

ernacional

de Nutrición Acuícola. 15-17

Noviembre. Universidad Autónoma de Nuev

o León, Monterrey, Nuevo León, México.

ISBN 970-694-333-5.

198

Introduction

It is known that a proportion of dietary amino ac

ids is excreted undigested and that individual

raw materials differ widely in this respect. Thus,

the higher the inclusion levels of raw materials

with low amino acid digestibility in diets formulat

ed on the basis of total amino acids, the less

reliable will be the prediction

of performance (Esteve-Garcia

et al.

, 1993; Fernandez

et al.

, 1995;

Pertillä

et al.

, 2001a). In this situation, costly safety

margins are usually applied to avoid

potential reductions in performance.

Knowledge of digestibility coefficients (DC) fo

r individual amino acids in

raw materials and the

requirement of digestible amino acids for a

defined production target (such as maximising

growth, breast meat yield and/or

profitability, or minimising feed

conversion ratio and/or feed

costs per kg gain or breast meat)

therefore enables formulation of

diets closer to the requirements

of the animals. Diets based on digestible amino acids may encourage the use of alternative

protein sources, because such formulations will

improve the precision of least cost diets and

reduce nitrogen output from poultry operations. Fina

lly, diet formulations on a digestible amino

acid basis may also offer economic benefits (Rostagno

et al.

, 1995).

A large volume of published data on the amino aci

d digestibility of raw

materials for poultry is

available, but there is consider

able confusion in the terminology

used due to differences in the

methodology employed for determining the DC

(Ravindran and Bryden, 1999). The different

methodological approaches of assessing amino aci

d digestibility are br

iefly reviewed, with

emphasis on ileal digestibility. The need for

correcting digestibility estimates for endogenous

amino acid losses will be highlighted, followed

by a discussion on the measurement of inevitable

losses. Finally, the concept of ‘standardizing’ il

eal digestibility values by correcting for basal

endogenous amino acid recoveries will be introduce

d, along with a table of “Standardized Ileal

Amino Acid Digestibility for Broilers” for a range of raw materials.

What is Digestibility?

Digestibility can be defined as th

e fraction of a certain nutrient i

ngested with the diet that is

absorbed by the bird, i.e. not excreted in the f

aeces. Digestibility can therefore be calculated by

measuring dietary amino acid input (AA

diet

) and excreta amino acid output (AA

excreta

) as follows:

Digestibility (%) = ((AA

diet

– AA

excreta

)/AA

diet

) x 100

The assay of digestibility has

become the most favoured techni

que for estimating amino acid

availability. Digestibility assays may be separa

ted into two main categories: excreta and ileal

digestibility. Excreta digestibility involves the co

llection of excreta from intact or caecectomized

birds. For measurement of ileal di

gestibility, the digesta are collected

from the distal part of the

ileum. The latter method is technically more

complex, but it eliminates some confounding

factors.