Data sheets: Peas

Introduction

Peas (Pisum sativum) are a fast-growing herbaceous legume that produce dehiscent pods containing several seeds that can be globular or angular, round or wrinkled, depending on the variety. Peas are highly genetically diverse. Selection and breeding programs have created many varieties that differ in flower color and shape and color of the pea, etc. One of the most important characteristics associated with both flower and pea color is tannin content, with white-flowered varieties producing peas without tannins. Peas are a good source of protein and energy, but their nutritional value is highly variable and depends largely on antinutritional factors (lectin and trypsin inhibitors), protein allergenicity, protein structure, and tannin and fiber content. The white-flowered hortense subspecies with a low concentration of antinutritional factors (5-5.5 IU trypsin inhibitor/mg DM) is the most widely used in the production of peas as a source of feed protein because its level of inclusion is not limited. It is a high quality, highly digestible, and palatable protein source, rich in lysine, but like other legumes, it is deficient in sulfur-containing amino acids. It has a low fat content (1%), a high starch content (43%), and about 4% sugar content. The fibrous fraction associated with the hull and seed coat is easily digestible in pigs (digestibility coefficient >70%), which allows for the use of the entire pea seed in most physiological phases of pigs, except in young animals. The limitation of its use in piglets is not only subject to its fiber but also to the difficulty of starch digestion and the presence of antinutritional factors, aspects that with heat processing favor its incorporation as a source of protein for piglets at weaning. Other technological treatments such as decortication or micronization together with heat treatment greatly improve the digestibility of protein and starch, although this increases the cost as a source of protein for pigs. In terms of their characteristics as a crop, peas are a cool-season crop that can be found both in spring and autumn, which in agronomy can be interesting in introducing the concept of double cropping, alternating short-season cereals with peas.

Comparative study of nutritional values

The systems used in the comparison are: FEDNA (Spain), CVB (the Netherlands), INRA (France), NRC (United States), and Brasil (Brazil).

¹There are no published data for peas in the BRASIL evaluation system, which does not include the ingredient in its system, since total pea production in South America does not exceed 2% of total world production.

Unlike other vegetable protein sources, pea protein is not very variable compared to other protein sources from the extraction industry where processing plays a very important role. However, the source of variation may be associated with the variety grown and the growing conditions that will determine both the digestibility of the protein and starch fractions and lead to changes in the proportion of fiber. Although peas are a source of protein included by most of the evaluation systems, BRASIL does not consider it as an ingredient because it is not an ingredient typically cultivated in South America.

For this review, the values used at the commercial level in the FEDNA, INRA, CVB, and NRC evaluation system tables have been chosen. It is observed that the protein content is very stable (CV<3%) and is not conditioned by the level of fiber (CV~7.5%), so that the fiber content, depending on variety and growing conditions, can be double the variation of protein without negatively affecting the final content. The variation in the protein digestibility coefficient is 3% with the two extremes being CVB (86% digestibility coefficient) and NRC (80% digestibility coefficient) while FEDNA and INRA, with similar digestibility coefficients, present intermediate values. It is important to emphasize that when the whole pea seed is used in the manufacture of feed, the type and content of fiber and starch determine the energy value and digestibility. In terms of net energy (NE), the values are very similar and the differences between the extremes are not more than about 100kcal NE/kg. While INRA and FEDNA present lower values (-50 with respect to the mean), CVB and NRC, with similar values, present the highest. These differences can be explained by a difference in the weighing given to starch digestibility and the fermentable fiber fraction in the energy prediction equations used by CVB and NRC. Starch content is not very variable (CV<2.6%) but INRA, although it gives the highest starch concentration of the evaluation systems, it estimates a lower value of NE for young animals while CVB with the lowest starch value estimates a higher value of NE assuming a negligible influence on the energy content associated with the sugar content (also not very variable). These differences are clearly reduced and standardized for sows and adult animals where the capacity of fiber fermentation and starch digestion reduces the differences between energy estimation values to <20Kcal/kg. In terms of total amino acids, taking lysine as a reference, it is observed that there are no great differences between FEDNA, CVB, and BRASIL (<1.5-2%) although NRC estimates values of almost +3% for lysine and isoleucine and +5% for tryptophan with respect to the average of the rest of the evaluation systems. However, it should be noted that peas have a low concentration of sulfur-containing amino acids compared to the rest of vegetable protein concentrates. With the exception of CVB, which gives higher values for sulfur-containing amino acids (+7%) and arginine (+3%), the rest of the systems present very stable values. The lysine digestibility coefficient presents a range between 79% and 83% (FEDNA, CVB, and INRA) with the extreme being 85% for NRC. The Ca, P, and phytic P mineral content is very low and small changes cause great variation (CV>5% to 10%) but with little impact at the applied level.

Recent findings

1. Net energy value of canola meal, field pea, and wheat millrun fed to growing-finishing pigs.

Two experiments were conducted to determine net energy (NE) values of soybean meal, Napus canola meal, Juncea canola meal, field pea, and wheat millrun using indirect calorimetry, and compare the determined NE values with the calculated NE values of the same feedstuffs based on a prediction equation. The study reported that, the NE value for SBM and canola meals can be predicted based on the DE value and the macronutrient composition of the same feedstuffs. However, the NE value for field pea and wheat millrun may not be predicted precisely based on the DE value and the macronutrient composition of the same feedstuffs.

2. Nutrient digestibility of heat-processed field pea in weaned pigs

There is a concern to include field pea grain in diets because of lower energy digestibility compared with soybean meal and corn grain and the presence of trypsin inhibitors that may affect protein digestion. Processing using heat and friction may reduce trypsin inhibitor activity in field pea grain and increase both energy and protein digestibility; however, its effect on weaned pigs remains unknown. However the present study showed that, cold-pelleting reduced trypsin inhibitor activity and increased the energy value of field pea grain, and extrusion reduced trypsin inhibitor activity and increased ileal digestibility of some amino acids compared with raw field pea grain fed to weaned pigs.

3. Growth performance of weaned pigs fed raw, cold-pelleted, steam-pelleted, or extruded field pea

Field pea is an alternative starch and protein source for swine; however, feeding raw field pea to weaned pigs may reduce feed efficiency (G:F). However, growth performance of weaned pigs fed field pea processed using treatments with heat, friction is unknown, and for this reason, it was aimed to study the impact of their inclusion in weanling diets. The study reported that, weaned pigs fed 400 g field pea/kg diet in substitution of SBM could maintain growth performance. Greater ADFI for field pea diets than SBM diet indicated that pigs compensated for the reduced energy value of field pea diets. Raw field pea can be included in late nursery diets without thermal treatment to replace 300 g SBM and 100 g wheat grain/kg diet.

4. Efficiency of pea seeds in sow, piglet and fattener feeding

Two varieties of pea, one white flowering (cv. Tarchalska) and one colour flowering (cv. Milwa), partly replaced soybean meal in the diet of sows and their progeny: piglets and growing pigs. The effect of a feed enzyme supplement was also determined on animal performance and carcass and meat quality estimated using standard methods.. The peas had little effect on the physical traits of the meat; they improved its water-holding capacity but did not change its colour and lightness. The variety Cv. Tarchalska significantly lowered all estimated sensory properties. It was concluded that pea seeds, especially the colour-flowering varieties, may be a suitable replacements of soybean meal, in moderate amounts, in the whole cycle of pig nutrition.

5. Prediction of the amino acid digestibility of legume seeds in growing pigs: a meta-analysis approach

However, the use of alternative ingredients such as legume seeds may help to reduce feed cost and environmental impact. In fact, legume seeds are an important source of essential amino acids (EAA) and can therefore be an alternative to oilseed meals. However, the accurate use of these legume seeds requires a precise knowledge of the standardized ileal digestibility of EAA, which may vary depending on its botanical variety. A meta-analysis was performed on available literature. Results showed that dietary CP and crude fibre (CF) were, respectively, the best predictors of each standardized ileal digestibility of EAA for faba bean, lupin and pea and soya bean (. For the dEAA content, the best prediction models included dietary CP and ADF for faba bean, lupin and pea and soya bean, respectively. Models developed in this study allow predicting the digestibility of EAA in these alternatives feedstuffs.

References

FEDNA: http://www.fundacionfedna.org/
FND. CVB Feed Table 2016. http://www.cvbdiervoeding.nl
INRA. Sauvant D, Perez, J, y Tran G, 2004, Tables de composition et de valeur nutritive des matières premières destinées aux animaux d'élevage,
NRC 1982. United States-Canadian Tables of Feed Composition: Nutritional Data for United States and Canadian Feeds, Third Revision.
Rostagno, H,S, 2017, Tablas Brasileñas para aves y cerdos, Composición de Alimentos y Requerimientos Nutricionales, 4° Ed