WHEAT: COMPOSITION AND FEEDING VALUE FOR POULTRY - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 246

Non-starch Polysaccharides
Non-starch polysaccharides are the main constituents of cell wall materials, and make up
the portion of plant tissue that is not digested by endogenous secretions in the digestive tract
(referred to in human nutrition as 'dietary fiber').
Cell wall polysaccharides in wheat are mainly arabinoxylans and (1→3),(1→4)-β-D-
glucans, but also contain small quantities of cellulose. On average, wheat contains about 12%
non-starch polysaccharides, of which approximately 8% is arabinoxylans, 2% cellulose and
1% β-glucans (Table 1). Some of the most important characteristics of soluble arabinoxylans
is their ability to absorb water and readily form viscous solutions or gels. It is known that
arabinoxylans and other non-starch polysaccharides (NSP) create viscous contents in the gut
of poultry and pigs, which impede the digestion of nutrients by reducing the mixing of
digestive enzymes with their substrates. This characteristic has long been recognized as a
factor limiting the use of wheat in poultry diets.
Protein
Protein is the second most abundant constituent of cereal grains, with the protein content
of commercial wheat varieties ranging from 8-16%, depending on variety and growing
conditions (Lasztity, 1999). The average crude protein content of wheat, however, is higher
than those of other cereal grains. Glutenin (high molecular weight protein) and gliadin (low
molecular weight protein) are the main protein fractions of wheat and each contribute
approximately 30-50% of the total protein content in wheat, with the albumins and globulins
each contributing 5-10% (Lasztity, 1999). The first two fractions are often referred to as
gluten.
The concentration in amino acids in wheats with different protein levels is shown in
Table 2. It can be seen that the amino acid concentrations increase linearly with increasing
grain protein levels and, in view of its high protein level, that it is a better source on amino
acids than corn. Therefore, wheat-based diets require less protein supplementation than corn-
based diets.
Endogenous Enzymes
Wheat kernel has its own enzymes that are responsible for the hydrolysis of endospermic
starch, releasing energy for growth of the developing embryo when sprouting begins (Stevens
et al ., 1988). In addition to ∞-amylases activity, xylanases are also present in wheat (Bonnin
et al ., 1998; Cleemput et al ., 1995) with a main function of degrading the walls of aleurone
and endosperm cells, during the germination stage making starch and storage proteins
accessible to aleurone derived amylases and proteases (Mares and Stone, 1973a,b). Wheat is
also known to have high activity of endogenous phytase which increase the availability of
phytate-bound phosphorus and this is responsible for the higher availability of wheat
phosphorus for poultry in comparison to most other cereal grains (Selle and Ravindran,
2007).