Grains such as wheat and barley, combined with legumes and oilseed meals,
provide not only the bulk of essential nutrients for commercial poultry production and
reproduction, but are also the prime source of anti-nutritive components,
which are likely to have significant bearing on how effectively all dietary
components are utilised by poultry. Sources of variation in the physical and
chemical characteristics of grains used in poultry diets include variety,
seasonal effects, and growth sites, crop treatment and grain fumigants, and
post-harvest storage conditions and period of storage. The available energy
and protein contents of grains fed to poultry, which best represent nutritive
value, are extremely wide and in consequence there is an urgent need to
develop rapid and objective tests for the assessment of nutritive value prior
to including grains in poultry diets. Variation in the available energy and
protein content of grains can be attributed to a wide range of anti-nutritive
factors such as non-starch polysaccharides (NSP), enzyme activity, tannins,
alkyl resorcinols, protease inhibitors, α-amylase inhibitors,
phytohaemagglutinins, alkaloids, saponins, and lathyrogens. The relative
importance of such factors will also differ according to the type of grain in
question. However, NSP seem to be the predominant factor in Australia over the
past few years given the volume of published literature on this topic. This
argument is strongly supported by the fact that NSP-degrading enzymes are
routinely used in monogastric diets with great success throughout the world.
Numerous attempts over a long period have failed to provide unequivocal
evidence that nutritive value in grains for poultry can be predicted with
sufficient accuracy and precision by simple, low-cost physico-chemical
measurements used singly or in combination. Nevertheless, it is highly
desirable to continue to explore these simple measurements in the expectation
that useful statistical relationships with more complex measurements will
emerge, or that simple measurements can be used to fine-tune prediction
equations based on more powerful techniques such as near infrared
spectrophotometry.
Finally, the nutritive value of grains for poultry will be determined not only
by the chemical and physical properties of grains but also by the way that
these interact with the processes of ingestion, digestion, absorption, and
metabolism in birds. For this reason it is imperative that plant and animal
scientists join forces to improve the nutritive value of plant material as
feed for animals for the benefit of grain growers and producers of livestock.
Turmeric (Curcuma Longa): An Underutilized Phytogenic Additive in Poultry Nutrition