Peas as an Alternative to Soybean Meal in Beef Cattle Finishing Diets

INTRODUCTION

Meat production currently faces numerous challenges, among which its dependence on global markets stands out.

• In particular, the use of soybean meal as the main protein ingredient in finishing feeds is raising increasing concern due to dependence on imports from third countries, where its production can have a considerable environmental impact (FEFAC, 2025).

To promote protein self-sufficiency, the European Parliament encourages the cultivation of protein crops, with peas standing out as they account for more than half of this production in Europe.

• Due to their high protein and starch content, this ingredient can replace both soybean meal and cereals in feeds (Cerisuelo, 2024).

However, their inclusion rate could be limited by the high ruminal degradability of their protein (Khorasani et al., 2001; Rotger et al., 2006), which can result in greater ammonia production in the rumen and promote a shift in nitrogen (N) excretion from feces to urine, where it may be more environmentally harmful because it is more prone to leaching and volatilization.

To date, there are no studies on the potential inclusion of peas in intensive finishing diets for beef-breed calves (the most common commercial type in Spain).

Therefore, the objective of this study was to determine, under these conditions, the impact of different pea inclusion rates replacing soybean meal and corn on technical and economic performance, ruminal fermentation, and nitrogen utilization.

TRIAL DESIGN

• The experiment was conducted at the La Garcipollera Experimental Farm (CITA-Aragón),

• using 32 male Parda de Montaña calves (210 ± 24.3 kg live weight and 152 ± 17.6 days of age at the beginning of the trial)

• under intensive finishing conditions, with feed and barley straw offered ad libitum until the animals reached 500 kg body weight.

The animals were allocated to four diets and received isoenergetic (11.7 MJ ME/kg) and isoproteic (13% crude protein) feeds that differed in the proportion of peas (0%, 15%, 30%, and 45% peas) replacing soybean meal and corn (hereafter 0%P, 15%P, 30%P, and 45%P, respectively).

Table 1. Feed ingredients

During the trial, the following were recorded daily:

• Individual feed intake using two ALPRO feeding stations (ALPRO Herd Management 7.0, DeLaval).

• Straw intake was calculated in relation to total intake (Costa-Roura et al., 2020).

The animals:

• Were weighed weekly to determine average daily gain (ADG) and feed conversion ratio.

• Blood samples were collected monthly to determine plasma urea concentration.

Ruminal fluid, fecal, and urine samples were collected at the beginning and end of the finishing period (Casasús et al., 2025) to characterize ruminal fermentation patterns and N balance across the different treatments.

• In ruminal fluid, pH, ammonia concentration (NH3-N), and the concentrations of different volatile fatty acids (VFA, including acetate, propionate, butyrate, and other minor acids) were determined.

• For the N balance, total daily N intake and its excretion in feces and urine were considered.

When the calves reached 500 kg, they were slaughtered at a commercial slaughterhouse.

After 24 hours of chilling at 4°C, the carcasses were weighed and carcass yield was calculated in relation to live weight before slaughter.

Carcass fatness and conformation were then determined by visual assessment (SEUROP conformation transformed according to an 18-point scale, and fatness 1–5 on a 15-point scale).

The economic results of the four diets were compared using a partial budget analysis.

The following technical and economic aspects were considered:

• Those affecting costs and revenues (ADG, days on feed, feed cost, carcass conformation, and carcass sale price),

• with the economic margin calculated as the difference between the revenues and costs described above (using 2017 prices).

A sensitivity analysis of feed cost was also performed in response to four scenarios with different relative costs of soybean meal and peas from 2010 to 2024 (Government of Catalonia databases, 2024), analyzed in constant 2024 euros.

The scenarios considered were as follows:

MAIN RESULTS AND DISCUSSION

The proportion of peas in the feed did not affect growth, total feed intake, or feed conversion ratio (Figure 1), which is consistent with other studies (Greenwell et al., 2018) and suggests that their amino acid content or degradability did not limit performance.

In fact, the 30%P diet resulted in an ADG 9% to 13% higher than the other diets and tended to reduce the finishing period required to reach the target slaughter weight.

• There were also no differences in carcass characteristics, with carcass weight, conformation, and fatness being similar among diets (Table 2).

Table 2. Effect of the proportion of peas in the feed on slaughter weight and carcass characteristics.

1 (Cold carcass weight / slaughter weight) × 100
2 Visual assessment (SEUROP classification)

Figure 1. Effect of the proportion of peas in the feed1 on growth, duration of the finishing period, feed intake, and feed conversion ratio.

1 Different letters (a, b) indicate significant differences among treatments (P<0.05).

Regarding ruminal fermentation, although all diets had a similar starch content, pH decreased and total VFA concentrations increased with increasing pea inclusion rate (Figure 2).

• The pH values remained within the normal range, well above those considered to cause subacute ruminal acidosis (<5.6, Nagaraja and Titgemeyer, 2007).

Regarding individual VFAs, propionic acid increased and the acetate:propionate ratio decreased, tending to be lower in the 30%P diet than in the 0%P diet (1.78 and 2.73, respectively, p=0.07).

• These results may be attributed to the greater degradability of pea starch compared with soybean meal and corn (Cerneau and Michalet-Doreau, 1991; Rotger et al., 2006), ingredients whose proportion in the feed decreased as pea inclusion increased.

Regarding ruminal protein degradation, NH3-N concentration increased with pea inclusion (Figure 2).

• This is consistent with other studies (Mendowski et al., 2021; Lobón et al., 2022) and may be explained by the fact that pea protein is highly soluble in the rumen and has greater effective degradability than soybean meal (Pereira et al., 2017).

Figure 2. Effect of the proportion of peas in the feed1 on ruminal fermentation patterns (pH and concentrations of NH3-N and volatile fatty acids)

1Different letters (a, b) indicate significant differences among treatments (P<0.05).

Figure 3. Effect of the proportion of peas in the feed1 on daily N intake, fecal and urinary N excretion, and N retention.

1 Different letters (a, b) indicate significant differences among treatments (P<0.05).

There were no differences among treatments in N intake or retention (Figure 3),

• which is consistent with the similar performance and feed conversion ratios observed and agrees with findings reported in dairy cows (Froidmont and Bartiaux-Thill, 2004; Vander Pol et al., 2008).

However, N excretion decreased in feces and increased in urine proportionally to the pea inclusion rate (Figure 3).

This would indicate greater ammonia loss in the rumen, possibly due to an imbalance between the energy and protein supply available for microbial growth.

• This excess ammonia is absorbed and metabolized into urea in the liver, which is released into the bloodstream and is largely lost through the urine (Calsamiglia et al., 2010).

This greater elimination of non-retained N through urine could have environmental implications because of its greater potential to contaminate air, soil, and groundwater in the form of ammonia, nitrous oxide, and nitrate (Dijkstra et al., 2013).

The economic results (Table 3) indicate that increasing the proportion of peas in the diets increased feed cost by up to 5%, but did not affect either total feeding cost or revenue from carcass sales (carcasses had similar weight and conformation).

Although the 30%P diet showed the best economic result (NS), the margin varied by only 3% between the highest and lowest values.

• If the cost per unit of protein or energy differs among ingredients, higher costs should be compensated for by an improved feed conversion ratio or a higher sale price (Froidmont and Bartiaux-Thill, 2004), which did not occur under our conditions, where final weight was fixed.

Table 3. Effect of the proportion of peas in the feed on economic performance.

Actual feed, housing, and carcass prices (2017).
1 Calculation based on days on feed
2 Calculation based on carcass weight and conformation (Table 2)

Figure 4. Effect of the proportion of peas in the feed on gross margin under different ingredient-cost scenarios1.

1 Scenarios: 1. Original (2017), 2. Maximum soybean meal cost (2022), 3. Maximum soybean meal cost/pea cost ratio (2021), 4. Minimum soybean meal cost/pea cost ratio (2012).

Finally, the sensitivity analysis under the four scenarios with different relative costs of soybean meal, peas, and the remaining ingredients is presented in Figure 4.

• Including peas in the diet resulted in a higher gross margin compared with 0%P in almost all scenarios, from the original scenario (1) to the maximum difference observed in Scenario 2 (with the maximum soybean meal cost recorded for 2022).

The profitability of intensive finishing diets is highly sensitive to fluctuations in ingredient prices.

• Thus, including peas is more profitable when soybean meal is expensive, but loses competitiveness when the opposite occurs.

Undi et al. (2024) also identified peas as a competitive alternative to distillers dried grains (DDGs),

• but warned that feed manufacturers may be reluctant to replace commonly used ingredients if alternatives do not have a stable supply and price over time.

Although the area dedicated to legume cultivation has increased considerably over the past decade, with Spain leading European pea production, its contribution to the feed protein market remains very low compared with imported soybean meal.

In this regard, in addition to their value in animal nutrition, the agronomic and environmental benefits of legume cultivation for soil and biodiversity should also be considered.

CONCLUSIONS

Our results indicate that, despite differences in ruminal fermentation and nitrogen utilization patterns, replacing soybean meal and corn with peas did not affect growth or feed conversion efficiency in finishing calves.

• Furthermore, the results support the economic potential of including up to 30% peas in feeds, although at the cost of increased urinary nitrogen excretion.

At the regional scale, it is necessary to assess whether the greater efficiency of pea crops in fixing atmospheric N in soils can offset the increase in N emissions from urine when peas are used in livestock feeding.

Acknowledgements