Author:
Ravindran V.,Bryden Wayne L.
Abstract
Methodology to evaluate the protein quality or amino acid availability in feed
ingredients for poultry using in vitro (enzymic,
chemical, or microbiological assays), indirect
in vivo (plasma amino acid assays), or direct
in vivo (growth or digestibility assays) measurements
has been reviewed. The specific applications and limitations of these methods
are examined. In vitro assays are useful in providing
information on heat damage in selected protein sources under defined
conditions, and on relative ranking of different samples, but they cannot form
the basis of practical feed formulations. While growth assays remain the only
direct means of confirming nutritional relevance of values obtained by other
procedures, in vivo digestibility assays appear to be
most useful, at present, to estimate amino acid availability. Amino acid
digestibility assays in poultry should be based on the analysis of digesta
from the terminal ileum rather than excreta, because of the variable and
modifying effects of hindgut microflora. Techniques used to estimate
endogenous amino acid losses in poultry are discussed. The needs for
correction of endogenous losses in amino acid digestibility calculations and
the relative merits of apparent and true digestible amino acid systems are
still being debated. It is, however, clear that both digestible amino systems
are superior to the total amino acid system currently employed to formulate
practical diets. Digestible amino acid values are likely to form the basis of
poultry feed formulations in the future. In particular, there is an urgent
need for more precise information on the variation in digestible amino acid
contents of locally grown ingredients and on the factors causing this
variation (e.g. variety, location, season, agronomic practices, processing,
etc.).
Subject
General Agricultural and Biological Sciences
Cited by
150 articles.
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