Requirements
for amino acids can be expressed in ideal amino acid profiles (defined as a
percentage of lysine) or in mg amino acids per gram of egg produced. Actually,
three different stages and corresponding ideal amino acid profiles can be
distinguished: growth, growth combined with (start of) egg production, and egg
production. Although all essential amino acids could be a limiting factor,
lysine is the most commonly observed limiting factor for growth because
development of muscle mass is at high level, while it is methionine during egg
production.
At the
start of egg production, feed intake capacity is still limited and might not
cover the nutritional requirements for amino acids which results in a
deficiency. Therefore, amino acid levels should be adjusted towards actual feed
consumption observed and egg mass produced. Later on in the production cycle,
requirements for e.g. digestible methionine reduce with approximately 12% from
60 weeks towards 90 weeks of age. However, birds within the same flock will
differ in their production performance level and consequently show variety in
their requirements for methionine. This stretches the approach that later on in
the production cycle, after growth has been finished (approximately 30-35 weeks
of age), amino acid levels should be determined based on daily egg mass
produced (deposition and egg weight) and not on the age of the birds.
Another important fact to take into account is that
the ‘average laying rate in percentage’ does not match individual performances
and it could be that two thirds of the flock performs above this average. If
the average laying rate is used to estimate the daily amino acid requirements,
this can lead to an underestimation of the actual requirements of most of the
birds. Because of differences between birds in performance, nutritional
requirements have to take into account flock uniformity by feeding and managing
the weakest birds while allowing the best birds to produce at their genetic
potential. This can be achieved by respecting a safety margin for the inclusion
of digestible amino acids in a situation where uniformity is low. If levels of
digestible amino acids are set above theoretical concentration (+5%) excellent
results can be achieved. To conclude, provide enough amino acids (take daily
egg mass and actual feed intake into account), keep flock uniformity in mind
and provide amino acids above theoretical requirement for excellent results.