Dr. Jacquie Jacob Ph.D., University of Kentucky
NOTE: Before using any feed ingredient, make sure that the ingredient is organic and that it is listed in your Organic System Plan and approved by your certifier.
Field peas are grown primarily in temperate regions, but are used as a food source worldwide (Castell et al., 1996). Traditionally, the poultry industry only made use of screenings left from milling field peas. Today there are varieties of field peas grown specifically for use in animal feeds. With the banning of meat and bone meal in animal feeds, and the fear of GMO-soybean meal entering the feed chain, the use of field peas in poultry diets has become more popular in Europe and Canada (Cowieson et al., 2003). With the increasing prices of soybean meal in the United States, field peas may become a feasible alternative here as well.
Different varieties of field peas are available. Genetics, seeding time and the agronomic conditions under which the peas were grown all affect the nutrient content of the harvested peas (Nikolopoulou, 2007). There are green-, brown- and yellow-seeded varieties of field peas. There is some variability in the average nutrient content among the different types of peas, but considerable variability among some pea varieties within each color category. Most of the differences are related to the size of the pea and the thickness of the hull. There is also variation due to genetics and growing conditions. When analyzing the different green-, brown- and yellow-seeded varieties of field peas, only the brown-seeded field peas were found to contain tannin (Igbasan et al., 1997).
Peas are valued as a source of both protein and energy. Reported protein contents range from 15.6% to 32.5% crude protein (Castell et al., 1996). As with most crops, the growing environment can affect protein content. Hot, dry growing conditions tend to increase protein content. The protein of field peas is highly digestible and has an excellent amino acid profile. Peas have high levels of lysine— more so than soybeans. Peas, like most of the pulse crops, are low in the sulfur-amino acids methionine and cystine. The amino acids of field peas and canola complement each other and are an alternative combination protein source available for poultry diets. The available energy content of field peas is similar to that of barley.
Starch is an important dietary source of energy. Compared to most cereals, field peas have a relatively high starch content (Laudadio and Tufarelli, 2010). Unfortunately, the starch is not as well digested in some varieties of field peas. There are two main classes of starches—amylose and amylopectin. The starches have different sizes, shapes and composition. The glucose molecules of amylose are connected to each other in chains with α-(1→4) linkages. In amylopectin, the chains of α-(1→4) linked glucose are connected in a highly branched structure with α-(1→6) linkages between the chains. Amylopectin is easier to digest than amylose. So the relative content of amylose and amylopectin will influence the digestibility of starch in field peas. Processing methods have been developed that improve starch digestion, such as micronization (Laudadio and Tufarelli, 2010). Micronization is a dry-heat process where infrared electromagnetic short waves are used to heat the grain. Micronization has been shown to improve the nutritive value of field peas (Laudadio and Tufarelli, 2010). Such procedures, however, may not be allowed in certified organic poultry diets—check with your certifying agency before feeding peas that have been processed using micronization. The addition of feed enzymes has also been shown to increase starch digestion for some field pea varieties (Cowieson et al., 2003).
Traditional use of field peas in poultry diets was restricted to the waste material from milling peas for human consumption. Such material should not be included in poultry diets at more than 15% (Igbasan and Guenter, 1996).
Field peas can be included in the diet of several different classes of poultry, although the recommended maximum levels differ greatly from one research report to another. Early studies recommended maximum levels for layer diets of 25% (Perez-Maldonado et al., 1999); 30% for broilers (Farrell et al., 1999); 25% for turkey starter diets; and 55% for turkey finisher diets (Savage, 1986). Commercial feed enzymes can be added to increase protein digestibility in diets containing high levels of field peas (Cowieson et al., 2003).
Today, peas can be a valuable energy and protein source for several different classes of poultry, as long as proper measures are taken to ensure that the diets meet specific nutrient requirements. New varieties with lower levels of trypsin inhibitors allow for greater inclusion of field peas without the need for roasting, which is required when using whole soybeans.
This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.