The need to feed a growing population leads to a trend for highly specialised
units where animals of high genetic merit are raised in optimum conditions.
Advances in husbandry techniques are also made in response to the needs
for rearing high genetic merit livestock.
Improvements in feed efficiency which have been gained over
the last decades are a further example of the improvements which have
been achieved from a combination of good breeding and good husbandry
techniques. The nutrition of livestock has played a critical and essential role
in these developments and is an element which needs to be continually updated as new scientific information becomes available.
Protein was recognised very early as an “organic body building substance”
of strategic importance to an organism. With the development of feed nutrient analysis early in the nineteenth century, the first qualitative assessment
of animal feeds was made possible. Yet, despite these developments, in
practice, diets continued to be dominated by the concept that formulations
were considered in terms of ingredients. New approaches are focusing on
dietary nutrient supplying independently of the ingredients per se. It is well
accepted that amino acids, as nutrients, are building blocks of protein and
play an essential role in the nutritional composition of a feedstuff. Historically
it was only the economic incentive which resulted in the use of supplemental
amino acids in feed formulation. However there has been a gradual evolution and more emphasis is now being given to supplement amino acids in
terms of sustainability and total nutrient supply.
Only as a result of developments in analytical techniques has it been
possible to demonstrate that an evaluation of protein to the point of
the effectively utilised essential amino acids is required to optimise
feed formulation and that this yields both practical and financial benefits. Over the last 2 decades crude protein concept has lost its overrated status which it had held since the start of nutrient evaluation.
The world population continues to increase, with over 9 billion people predicted in 2050. Correspondingly the requirement for protein
to feed the increasingly affluent world population will rise. Thus as
agricultural production becomes ever-more concentrated in specific
regions it becomes even more important to use all natural resources
as wisely and sparingly as possible. In this respect, the concept of
sustainable agriculture is not solely related to animal production but
also incorporates all aspects of animal feeding and the use of feeding
regimes adjusted to demand.
Amino acids are essential nutrients which are an integral part of these
feeding regimes. In most instances they may substitute feed protein
sources, helping to save and spare protein, reduce nitrogen excretion
and minimise greenhouse gas emissions. In the future, amino acids
will become even more important to ensure that animal production
systems are environmentally sustainable and make optimum use of
the limited natural resources.
History of amino acid use in animal feed
Over the last 60 years the availability of supplemental amino acids
has provided producers of feed and animal protein to maintain the affordable supply of food while society has greatly changed and grown
its consumption.
Without amino acids it would have been very difficult, if not impossible,
to produce the quantity of meat, milk, fish and eggs demanded by European consumers. The availability of amino acids has allowed feeds
to be produced using smaller quantities of protein rich raw materials
allowing these limited scarce resources to be used more sparingly.
Starting in the 1950’s with methionine, amino acids have enabled fish
meal to be eliminated from meat and egg production and at the same
time allowed poultry producers to increase production based upon the
use of vegetable protein sources. Availability of lysine in the 1960’s
has allowed these developments to progress further and be replicated
in other species. Since then the amino acids threonine, tryptophan,
valine, isoleucine, histidine, and arginine have all become available.
Amino acids and mixed feeds
Compound feeds used either as the sole component of a diet or as
supplements to other feed materials, represent the major part of the
total agricultural economic outlay and remains one of the most important concepts in agriculture.
The past decade has seen major increases in compound feed production coupled with a trend towards larger livestock units and higher
performance levels. This has increased the importance attached to
the utilisation of new findings in the areas of physiology of nutrition
and in the design of new compound feed formulas. These developments place continuously higher demands on the formulator to
produce feeds capable of meeting the requirements for high performance, cost-effective and environmentally friendly feeds. The following diagram shows the result of a very simple experiment with only one small supplement of an amino acid to a pig feed (Figure 2).
Without using amino acids, lowering the protein content of the feed
by 2% from 18 to 16% in the starter and 16 to 14% in the finishing
diet, resulted in poorer growth (-2% crude protein no amino acids)
compared with the controls (control no amino acids). However, after
the addition of lysine to the low protein diets (-2% crude protein with
amino acids) the level of performance was raised to that of the controls. Moreover, the pigs given the low protein diets with supplemental
lysine excreted significantly less nitrogen compared with the controls.
For many years, amino acids have provided the opportunity to achieve
improved animal performance coupled with a saving in protein use
and above all at a lower cost for animal production. In addition to
these benefits, both animal producers and consumers have become
increasingly more aware of the additional positive effects such as improved animal health and a reduced nitrogen load on the environment.