Air classification and other methods of separating peas into their component fractions produces byproducts which are suitable for use in the poultry feed industry. Coarse "pea chips" were examined in diets for male broilers up to 3 weeks of age. The AMEn was 2748 and 2696 kcal kg-1 (DM basis) for yellow and green pea chips, respectively (Igbasan and Guenter 1996{11}), which agrees with AMEn values of whole peas (Igbasan and Guenter 1996{10}). Coarse milling did not affect the amino acid distribution within the different size classes of pea particles (Leterme et al. 1990{127}). A technique which isolated the central part of pea cotyledons elevated starch while reducing protein and fibre levels (Otto et al. 1997{6}; Kosson et al. 1994 {24}).
Pea protein concentrate, a high-protein fraction derived from air classification of ground pea particles, is effective as a nutritive pellet binder ( 25g PPC kg-1 diet). However, fine pea particles should never be fed unpelleted as the diet will adhere to the inside of the beak, causing difficulty eating and beak necrosis (Brown, 1991).
Peas should be analyzed regularly for CP and fibre levels. Samples of a single pea variety ranged from 14.5 - 28.5% CP (dry, dehulled basis), indicating that environment has a large impact on pea protein variability (Reichert and MacKenzie 1982{133}). Fibre levels may also warrant analysis because a high crude fibre level (99 g kg-1) was implicated in the reduced AMEn content of peas for birds in-lay (2525 kcal kg-1, as fed; Askbrant and Hakansson, 1984{128}). Peas may be harvested at up to 20% moisture in an attempt to reduce split and cracked seeds; therefore, moisture content should be assessed regularly.
Pea CP levels are determined on the basis of nitrogen content. Non-protein nitrogen was present in the seeds, which reduced the true nitrogen-to-protein conversion factor (5.25) from that normally used (6.25). However, it is recommended that all CP calculations continue to use the 6.25 factor, lest peas appear at a disadvantage to the similarly inaccurate protein calculations of other feed ingredients (Sosulski and Holt 1980{139}; Mosse 1990{76}).
Producers who grow and utilize their own feedstuffs
should be aware that fertilization practices can affect the nutrient
profile of peas. Sulfur deficiency reduced the production of
legumin, a storage protein that contains methionine and cystine
(Evans et al. 1985 {127}), but sulfur fertilization increased
the total sulfur amino acid content of peas by 10% (Eppendorfer
and Eggum 1995{19}). Nitrogen and phosphorus fertilization increased
the seed content of these elements, and inconsistently improved
seed yield (Browning and George 1981{136}). These plants were
grown in sterilized soil, and consequently a similar nitrogen-related
improvement may not be seen in peas innoculated with Rhizobium
bacteria. Normal fertilization practices are likely to support
the growth of peas with maximized nutrient values.