Alberta Agriculture Food and Rural Development,6909 116 Street,
Edmonton, AB, T6H 4P2, Canada
Take Home Messages
Pea grain has not been widely used in diets for ruminant animals, partly because of cost and partly because of lack of information on the nutritive attributes of peas. Peas, like other legume grains, are characterized by the rapid ruminal degradability of the protein and slow degradability of the starch. Peas are a good source of protein and energy for the ruminant.
The nutrient composition of field peas grown in Alberta is given in Table 1. Peas contain approximately 24% crude protein, twice as much protein as barley grain, and two-thirds that of canola meal. The quality of this protein (rumen undegradable) is low relative to grains and other supplemental protein sources. The rumen undegradable or bypass protein content of peas is 22% (15) compared to 35% for canola meal (5) and 27% for barley grain (15). These low levels of rumen escape protein may not be a problem for ruminant animals at modest levels of performance, as the majority of protein needs can be met by microbial protein. However, in highly productive animals, peas may not provide adequate amounts of bypass protein which will necessitate supplementation of the diet with high bypass protein sources. The energy content of peas is higher than barley and is close to that of corn and wheat. The calcium, phosphorus, magnesium, and sulphur content of peas is similar to that found in cereal grains grown in Alberta. The potassium content of peas is approximately twice that normally found in cereal grains. The trace element content of peas is the same as that found in barley grain grown in Alberta. Peas are low in copper, manganese, and selenium and are marginal in zinc content. This is not surprising as the trace element content of feedstuffs is a reflection of the availability of the trace elements in the soils on which they are grown. Most crops grown in Alberta are deficient in these trace elements.
Table 1. Average nutrient composition of Alberta grown field peas (100% dry matter basis).
|Dry matter, %||91.6|
|Crude Protein, %||23.7|
|Rumen Undegradable Protein, %2||22|
|Digestible Energy2, Mcal/kg||3.84|
1 Alberta Agriculture Food and Rural Development based on 72 samples from 12 cultivars.
2 NRC 1989 Nutrient Requirements of Dairy Cattle.
3 Fonnesbeck, et al. (9).
Peas, like other legume seeds are characterized by having highly degradable protein and relatively slowly degradable starch. The protein in peas is completely digested by ruminant animals. Pea protein is highly soluble with a low rumen escape or bypass protein content. The National Research Council (15) assigns a bypass protein content of 22%, based on 4 measurements. This appears to be reasonable based on unpublished work in Alberta (11, 18). Peas have a higher level of soluble protein and a relatively slower rate of digestion of the degradable fraction in the rumen (2). Pea protein disappearance rate was approximately 1.6% per hour compared to 4.5% for soybean meal after 6 hours of rumen incubation time (Figure 1). As pea protein is completely degraded by ruminants, this suggests that the non-soluble, slowly degradable fraction is about 38%. The relatively slow initial rates of degradation has been observed in other studies (14). Degradation rate of pea protein from 6 to 12 hours of incubation appears to be similar to soybean meal. This may be advantageous in providing a more sustained release of nitrogen needed for rumen microbial growth. The comparatively low bypass protein content does not appear to be of significance for ruminants at low to moderate levels of performance.
The energy content of peas is similar to corn and wheat. Based on a compilation of research on site of digestion of starch in various feedstuffs Nocek (16) showed that approximately 76% of the starch in peas is rumen degradable with the remaining 24% escaping to the small intestine. By comparison, barley had about 87.5% rumen degradable starch and 12.5% escape starch. The starch content of peas ranges from 41 to 54% of the dry matter with approximately 50% of this being soluble. The non-soluble, rumen degradable fraction has a slow rate of degradation in the rumen (21). In high concentrate diets the ruminal degradation rate of pea starch is similar to corn and much slower than wheat, oats, or barley (Table 2).
Table 2. Ruminal degradability characteristics of starches from selected feed ingredients.
|Total Starch||Soluble Starch||Rumen Degradation Rate % Hr-1|
|% DM||% Starch||Slow||Fast|
Source: Robinson & McQueen (19).
A slow starch degradation rate would help control rumen pH which is especially important in animals that that are fed large amounts of grain. Fiber digestion is depressed at a rumen pH below 6.0 which contributes to reduced dry matter intake, milk fat depression, and increased digestive disturbances. A positive effect on rumen pH associated with the relatively slow starch degradation of peas has been demonstrated (Figure 2) with cows fed concentrates at 70% of ration dry matter twice daily by rumen cannula (20). This slow rate of starch degradation may also explain why high producing cows fed high grain diets had higher milk fat percentage when peas comprised a significant proportion of the concentrate (6).
Calves and Replacement Heifers
Peas have been successfully fed to young calves in a University of Alberta study (7). Ten female holstein calves were fed a 20% crude protein concentrate containing 50% peas as a replacement for barley, canola meal, and soybean meal (Tables 3 and 4).
The calves were one to four weeks post weaning at the beginning of the experiment. Both concentrates were consumed readily by the calves. Average daily gain, dry matter intake of concentrate and hay, and feed conversion efficiency were not different for the control and pea based concentrates (Table 5). These data indicate that peas can be used as a replacement for other protein sources in the starter rations for young calves. No work has been reported on the maximum level at which peas can be included in starter rations. However, there does not appear to be an upper limit on the amount that can be included in practical rations.
Table 3. Composition of concentrates.
|Ingredient||Control, %||Peas, %|
|Soybean Meal - 48||10.2||2.0|
|Meat and Bone Meal||1.0||1.0|
|Trace Elements/Vitamin Premix||+||+|
Table 4. Chemical composition of the experimental concentrates and hay.
|Dry Matter, %||84.5||83.5||87.5|
|% of dry matter|
|Neutral Detergent Fibre||21.0||18.4||67.9|
|Acid Detergent Fibre||7.1||7.0||38.9|
No work has been reported on the use of peas in replacement heifer rations. Beacom (4) conducted an experiment with light weight (160 kg) growing beef calves in which an 11% crude protein basal ration composed of 71% ground crested wheatgrass hay, 25% rolled wheat, and 2.9% acidulated fatty acids plus vitamins and minerals was fed. Six percent ground fababeans, field peas, or canola was added to the basal ration. Supplementation with the fababeans or peas increased daily gains and reduced feed to gain ratios by 12% compared to the basal ration. Supplementing with canola increased daily gains by 8% and improved feed efficiency by 9%. The canola contained slightly more protein (26% vs. 24%) than the peas. The greater improvement in performance of the calves fed peas, could be due to the higher starch and therefore higher energy content of the peas compared to the canola. More recent work (17) in which a barley/soybean meal based control ration was fed to 263 kg beef calves on a backgrounding diet demonstrated that the substitution of peas for barley and soybean meal on an equal protein basis resulted in similar dry matter intake, rates of gain and feed efficiencies (Table 5). These rations contained 14% crude protein and were composed of 70% concentrate and 25% oat hay. The growth rates of these calves was excellent at 1.38 to 1.39 kg per head per day, indicating that peas can be substituted for barley and soybean meal and still promote superior performance. The performance of the animals in these trials suggests that peas can replace mixtures of barley, canola meal, and soybean meal in the diets of replacement heifers as a source of protein and energy without impairing performance.
Table 5. Substitution of peas for canola meal, barley, and soybean meal in the diets of young calves.
|Initial body weight, kg||70.0||66.8|
|Average daily gain, kg||0.82||0.79|
|Dry matter intake, kg/d|
|Feed/Gain, kg DM/kg||3.41||3.14|
Source: de Boer et. al. (7).
Table 6. Effect of substitution of peas or hulless oats for barley and soybean meal on the performance of backgrounding calves.
|BW, kg||DMI, kg||ADG/kg||G/F|
ab Means within columns with unlike superscripts are different (P<.05)
Lactating dairy cows require large amounts of protein in their diets. Dietary protein requirements of 18 to 19% during early lactation and 16 to 14% during mid and late lactation are needed. Rumen undegradable or bypass protein is also required since rumen microbial protein production is not adequate to meet the needs of superior producing animals. Peas have a low bypass protein content compared to common protein supplements such as canola meal and soybean meal. The need for bypass protein is greatest during early lactation and declines as lactation progresses. Pea protein has been successfully substituted for soybean protein in late lactation cows in a study conducted at the University of Alberta (13). The soybean meal diet was formulated to satisfy the nutrient requirements of a Holstein cow weighing 600 kg and producing 22 kg of 3.5% fat milk at 200 days in lactation. A TMR consisting of 25% alfalfa silage, 25% brome grass silage, and 50% concentrate was fed ad libitum, twice daily. Four different 18.6% crude protein concentrates were used in which pea protein replaced soybean protein at 0, 33, 67 and 100%. Barley was the major grain source. Daily milk production, 4% fat corrected milk (FCM) production, and dry matter intake were not affected as the level of peas was increased (Table 7). This suggests that for late lactation cows, peas can completely replace soybean meal in the diet. Rumen fermentation and forestomach digestion of these diets were also compared (12). Based on the rumen fermentation characteristics and on nutrient flow to the duodenum, Khorasani et al. concluded that pea protein can replace about 70% of soybean meal protein in diets of late lactation dairy cows.
Table 7. Effect of substitution of pea protein for soybean meal protein on milk production and dry matter intake in late lactation dairy cows.
|Pea protein, %||0||33||67||100|
|Milk yield, kg/d||20.7||22.0||21.4||21.7|
|4% FCM, kg/d||20.2||21.8||21.9||20.7|
|Dry matter intake, kg/d||21.2||21.5||21.9||21.6|
Source: Khorasani et.al. (13).
Similar results were obtained in a field trial with a commercial dairy herd (22). A test concentrate contained 25% peas in place of canola meal, soybean meal, and barley (Table 8). The concentrates were isonitrogenous and were formulated to contain equal proportions of bypass protein (Table 9). Cows producing 45 kg milk were fed up to 1.4 kg daily of a commercial 36% crude protein supplement.
Table 8. Composition of concentrate mixtures.
|Ingredient||Control, %||Pea, %|
|Corn Gluten Meal||1.0||0|
Table 9. Nutrient composition of concentrate mixtures.
|Crude protein, %||16|
|Crude fiber, %||7.5|
|Vitamin A, IU/kg||8000|
|Vitamin D, IU/kg||1500|
|Vitamin E, IU/kg||15|
Concentrates were fed twice daily according to level of milk production. Alfalfa silage was fed free choice along with 3.5 kg of alfalfa/grass hay per head daily. During the five months of this trial, milk production averaged 24 kg/cow/day. Milk production was not significantly different between control cows and those fed the pea based ration except for the month of April (Table 10). Fat test did not differ between groups during the trial.
Table 10. Milk yield of a commercial dairy herd fed a soybean/canola meal based concentrate compared to a pea based concentrate.
|Milk Yield, kg d-1|
a,b Means with different superscripts are significantly different P<0.05.
Ward et.al., 1990.
These results indicate that peas can be used to replace other protein sources in diets of cows at modest levels of production.
The bypass protein content of peas is approximately 22% of the crude protein and is lower than most of the more common protein supplements (15). This low bypass protein content makes it difficult to formulate rations for early lactation and high producing cows utilizing large amounts of peas. To address this concern, a field trial was initiated in a high producing herd to see if practical rations could be formulated using peas as a protein source while maintaining peak milk yield as well as average production (6). Two 18.5% crude protein concentrates were formulated to contain similar amounts of bypass protein using meat meal and distillers grains. Soybean meal and canola meal were used in the control ration while the test ration contained 25% peas. Barley was the grain used in both mixes. The concentrates were fed through a computer controlled feeder according to level of milk production. A 50% alfalfa silage, 50% whole plant barley silage mixture was fed free choice along with 2.3 kg of alfalfa hay/cow daily. Milk yield ranged between 32 and 34 kg for the 6 month duration of this experiment. Milk yield peaked at approximately 60 days in milk and did not differ between the cows fed the pea based ration (40 kg/day) and the soy/canola based ration (41 kg/day). Persistency of milk production did not appear to be affected by concentrate source. During early lactation (1-100 DIM) milk yield was not affected by protein source, however fat test was higher for the cows fed peas as was fat corrected milk (FCM) production (Table 11). This suggests that peas can be used in rations that are balanced for undegradable protein with no adverse effect on peak milk yield. The higher fat test seen in early, mid, and the complete lactation suggests that rumen pH may not be depressed as much as with barley based diets. This could be due to less dramatic effects of peas on acetate:propionate ratios than is observed when barley is fed. In this study the grain portion of the pea based concentrate was 75%, including the peas; and 67% for the soy/canola based concentrate. During mid lactation, milk production was significantly less for the cows fed the pea based concentrate and as a consequence production during the entire trial was significantly lower for this group compared to the soy/canola group. During mid lactation, first calf heifers fed the pea based concentrate exhibited a 17% reduction in production which may be a reflection of their greater need for growth as multiparous cows were not affected similarly. Both test groups contained 40% or more first lactation animals. This trial indicates that peas can be used in rations for high producing animals fed properly balanced rations. In high producing dairy cows the use of peas should be limited only by the cost of providing adequate bypass protein.
Little research has been reported in the scientific literature on the effect of processing on the nutritive quality of peas for ruminant animals. Work at Agriculture Canada, Lethbridge Research Station using esophogeal fistulated animals, has shown that peas do not survive chewing intact (18). This observation, along with the large kernal size of peas suggests that the nutritive value of peas will not likely be improved by processing methods usually employed by the dairy industry.
Peas are usually ground before incorporation into pelleted feeds. Inclusion of peas in pelleted concentrates generally improves pellet quality, resulting in more durable pellets with less fines produced with mechanical handling (3, 7).
Heat processing is often employed to denature protein in feedstuffs which can result in an increase in its bypasss protein content. Heat processing of cereals can result in gelatinization of the starch which increases the rate and extent of runimal degradation. As the protein in peas is highly degradable in the rumen, heat processing may improve the quality by increasing the bypass fraction. On the other hand, heat could increase the ruminal degradation of the starch, which may not be helpful. Steam flaking of peas (8) at 100C has been shown to have no effect on degradability of protein or on gelatinization of starch and as a consequence this process did not affect ruminal digestion or flow of protein and starch to the small intestine. As starch digestion was not affected by steam flaking, ruminal pH was not affected.
Table 11. Milk production and milk composition for cows fed pea or soy/canola meal supplemented diets.
|Soy/conola meal based||Pea based||SE|
Production, kg d-1
Production, kg d-1
ab Means within rows with different superscripts are significantly different P<.05.
Extrusion, on the other hand, resulted in gelatinization of the starch (8, 21). The difference in the effect of heat processing on starch gelatinization seen in these experiments may be due to the higher temperatures or the combination of time, temperature, and pressure involved in the extrusion process compared to steam flaking. Extrusion of peas produced a marked increase in rumen soluble starch content of the peas and in the extent of ruminal starch degradation (21). Total volatile fatty acid (VFA) production was increased when extruded peas were fed compared to ground peas (8) with a resulting drop on ruminal pH. Presumably this occurred because of an increased rate of ruminal starch degradation since the extent of ruminal degradation of the starch was not affected by extrusion. The gelatinization of the starch resulting from heating (extrusion) has resulted in a 53% increase in rumen microbial protein production (8) due to the increased fermentation of starch in the rumen. Therefore the effects of heat processing on digestion of pea starch in the rumen may be beneficial in that it increases microbial protein production, but it may have a detrimental effect on rumen pH.
Peas are low in bypass protein content and pea protein is highly soluble. Processes that would increase the bypass protein content, reduce solubility, or decrease the rate of ruminal protein degradation would improve the relatively low quality of pea protein for ruminants. Steam flaking has had no effect on protein degradability (8). Autoclaving or extrusion has dramatically decreased the soluble protein content of peas (2, 8, 21), rate of degradation of the non-soluble, rumen degradable fraction (2) and increased the slow rumen degradable fraction (21). Extrusion temperatures from 140C to 220C did not decrease the total tract digestibility of pea protein, suggesting that denaturation of the protein was not sufficient to result in over protection of the protein (21). These data suggest that heat processes hold promise for improving the protein degradability characteristics of pea protein. More research is needed on practical methods of treating peas to improve protein quality for ruminants.
Peas appear to be very palatable. Young calves readily consumed a starter concentrate mix containing 50% peas (7). Lactating dairy cows exhibited no change in concentrate consumption when abruptly changed from a barley, canola meal, soybean meal based concentrate to one containing 25% peas (22). In one field trial (6), fewer problems were observed in training first calf heifers to use a computer controlled concentrate feeding station when a pea based concentrate (25% peas) was used compared to a commercially prepared concentrate. Both concentrates were made with rolled barley mixed with a pellet containing all other ingredients.
Peas can be used as a major source of supplemental protein for ruminants. The amount of peas that can be used should be governed by the cost of competing protein sources and the cost of providing higher bypass protein supplements for highly productive animals. Processing does not appear to be necessary. Heat processing through extrusion or roasting should markedly improve the bypass protein content of peas. The relatively slow degradation rate of starch in peas may be beneficial to animals fed diets containing a high concentration of grain by lessening the decline in rumen pH. This benefit would be greatest when grains with a rapid rate of starch degradation, such as barley, are used.
1. Alberta Agriculture, Food and Rural Development, Crops and Soils Diagnostic Center, Edmonton, Alberta, Canada, T6H 4P2
2. Aguilera J.F., M. Bustos and E. Molina. 1992. The Degradability of legume seed meals in the rumen:effect of heat treatment. Anim. Feed Sci. Technol. 36:101.
3. Atkins R., Federated Cooperatives Ltd., Edmonton Alberta. Personal communication.
4. Beacom S.E. 1985. Using farm grown feeds as protein supplements in rations for growing beefcalves. Miscellaneous circular. Agriculture Canada Research Station, Melfort Sasketchewan, Canada.
5. Canola Council of Canada, 1993. Canola Meal Feed Industery Guide. D Hickling editor. Winnipeg, Manitoba, Canada, R3B 0T6
6. Corbett R. R., E. K. Okine and L. Goonewardene.1994. Effects of feeding peas to high-producing dairy cows. Can. J Anim. Sci. 75:625-629.
7. de Boer G., R. R. Corbett and J.J. Kennelly. 1991. Inclusion of Peas in Concentrates for Young Calves. 70th Annual Feeders Day Report, University of Alberta.
8. Focant M., A. Van Hoecke and M. Vanbelle. 1990. The Effect of Two Heat Treatments (Steam Flaking and Extrusion) on the Digestion of Pisum sativum in the Stomachs of Heifers. Anim. Feed Sci. Technol. 28:303.
9. Fonnesbeck, P.V., H. Lloyd, R. Obray and S. Romsberg. 1984. I.F.I. tables of feed composition. International Feedstuffs Institute, Utah State University, Logan UT 84322.
10. Hodge R. W. and B. Bodganovic. 1983. Feeding hay supplemented with peas or low protein oats to crossbred lambs born in the spring. Australian Journal of Experimental Agriculture and Animal Husbandry. 120:19.
11. Khorasani G.R., University of Alberta. Personal communication.
12. Khorasani, G.R., E. Okine, R. Corbett and J.J. Kennelly. 1995. Ruminal fermentation and forestomach digestion pf peas by dairy cattle. Ann Zootech 44 suppl:180
13. Khorasani G.R., E. Okine, R. R. Corbett and J.J. Kennelly. 1992. Peas for Dairy Cattle. 71st Annual Feeders Day Report, University of Alberta.
14. Lindberg J.E. 1981. The Effect of Basal Diet on the Ruminal Degradation of Dry Matter, Nitrogenous Compounds and Cell Walls in Nylon Bags. Swedish J. Argic. Res. 11:159.
15. National Research Council. 1989. Nutrient Requirements of Dairy Cattle. Sixth Revised Edition, Update 1989. National Academy Press, Washington D.C., USA.
16. Nocek, James E. 1996. Fuel for milk: delivering carbohydrate to the rumen and intestine at the right price. In Advances in Dairy Technology. University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
17. Poland, W.W., D.G. Landblom, and R.L. Harrold. 1996. Feeding value of field pea and hulless oat in growing calf diets. J. Anim. Sci. 74 Suppl1:279
18. Rode L., Agriculture Canada, Lethbridge Alberta. Personal communication.
19. Robinson P.H. and R.E. McQueen. 1989. Non-structural Carbohydrates in Rations for Dairy Cattle. Proceedings of the Western Canadian Dairy Seminar.
20. Valentine S.C. and B.D. Bartch. 1987. Fermentation of Hammermilled Barley, Lupin, Pea and Faba Bean Grain in the Rumen of Dairy Cows. Anim. Feed Sci. Technol. 16:261.
21. Walhain P., M. Foucant and A. Thewis. 1992. Influence of extrusion on ruminal and intestinal disappearance in sacco of peas (Pisum sativum) proteins and starch. Anim. Feed Sci. Technol. 38:43.
22. Ward D., R.R. Corbett, W. Slack and L. Goonewardene. 1989. Field Peas as a Protein Source for Lactating Dairy Cows. Farming For The Future Project Number 89-F023-5, Alberta Agriculture and Rural Development.