Agriculture Reference
In-Depth Information
6
Basics and Applications of an Exponential
Nitrogen Utilization Model ('Goettingen
Approach') for Assessing Amino Acid
Requirements in Growing Pigs and Meat
Type Chickens Based on Dietary
Amino Acid Efficiency
F. Liebert*
Georg-August-University Goettingen, Goettingen, Germany
Abstract
Validated protein evaluation systems are required for improved efficiency of protein conversion pro-
cesses in food producing animals. Up to now, different procedures have been developed to connect feed
protein evaluation based on the value of individual amino acids and estimates of the individual amino
acid requirement. An exponential function for the relationship between intake of the limiting amino acid
in the diet and observed response on nitrogen deposition in the body is utilized within the 'Goettingen
approach'. This approach has the potential to model the process of converting feed into food protein by
taking into account an efficiency-based optimized dietary amino acid supply at a desired level of per-
formance within the estimated threshold value of genetic potential for growth. This chapter provides an
overview of the basics and current applications of the procedure. Finally, the results are applied to give
conclusions about the ideal dietary amino acid ratio for growing pigs and growing chickens. An import-
ant factor that may impact both on the derived requirements and the resultant ideal dietary ratios is the
variation of amino acid efficiency in feed. This factor has not been systematically investigated.
Introduction
utilization processes in the 'black box' of
food producing animals and in human be-
ings. As a consequence, based on nitrogen
(N) balance studies, fundamental concepts
were developed to provide comparable infor-
mation about the protein value of individ-
ual feedstuffs or diets. Parameters like net
protein utilization (NPU) according to Block
and Mitchell (1946) or biological value (BV)
as applied by Mitchell (1924) yielded first
Evaluation of feed protein quality is, today,
a 'must have' for modern farming systems
and a precondition to fulfill actual needs
both for resource management and sustain-
ability of processes to convert feed to food
protein for human nutrition. Several gener-
ations of nutrition scientists created con-
cepts to improve the basic knowledge about
