Wheat, like many other cereals, can vary widely in chemical composition because it is highly affected by cereal cultivar, soil type, environmental conditions and fertilization. However, most wheat used in feeds has 10 to 15 percent crude protein.
Wheat vs. maize
Wheat contains 50 percent more lysine and 300 percent more tryptophan than maize and has about the same amino acid profile (as relates to protein) as barley. Therefore, wheat-based diets need less protein supplementation than maize-based diets. Amino acid digestibilities in wheat are not drastically different from those in maize with digestibilities of lysine, methionine, threonine and tryptophan of 72, 84, 70, and 79 percent compared to 68, 85, 69, and 67 percent in maize.
The crude fiber concentration in wheat is 2 to 3 percent the same as in maize. However, wheat has only 1.5 to 2 percent lipids compared to 3 to 4 percent for maize, which contributes to the lower energy content compared with maize (about 95 percent the energy of maize).
Mineral concentrations in wheat are about the same as in maize. However, wheat has natural phytase that releases phytin phosphorus, much like an exogenous phytase. Thus, wheat has a phosphorus digestibility of 50 percent as opposed to just 15 percent in maize; this gives a digestible phosphorus value of 0.19 percent versus 0.04 percent for maize. Vitamin and trace mineral concentrations in wheat are not different enough from maize to justify changes in vitamin or trace mineral premixes when changing from maize to wheat.
Feeding Value . Wheat has been reported to have a feeding value 92 to 100 percent of maize. Wheat has 10 to 15 percent more digestible energy than barley and has about a 5 percent higher feeding value than sorghum. The feeding value does not differ among soft and hard varieties of wheat, or white and red varieties. Actually, within varieties, inherent variability (due to environmental conditions) may cause greater fluctuation in energy concentration than among varieties.
A test weight between 680 and 800 g/L does not affect energy concentration, but when test weight falls below 680 g/L, then energy density will most likely be affected. Frost damaged, or partially sprouted wheat has been shown to have the feeding value of normal wheat.
Particle Size. Pig research has shown consistent and significant increases in digestibility of nutrients and performance as particle size is reduced, but this has not been confirmed in poultry. Similarly, in pigs fine grinding has been blamed for increased stomach ulceration. However, more than one stressful factor seems to be needed for development of severe stomach ulceration. In contrast, poultry can be fed diets based in full or part on whole wheat without loss of performance, but this requires careful planning of the whole nutrition program.
Enzyme supplementation . Wheat contains a significant amount of non-starch polysaccharides known as pentosans, in addition to beta-glucans (which abound in barley). Pentosans are considered the primary source of anti-nutritional activity in wheat. In several research reports, the inclusion of enzymes to break down these anti-nutritional compounds has resulted in improved growth performance in pigs. But practical results have been variable, perhaps because wheat variety plays such a huge role in the response of pigs to enzymes. In contrast, results appear to be more consistent in poultry, where such enzymes as pentosanases and glucanases are used quite frequently.