Soybean meal is a widely used and palatable protein supplement for high producing dairy and beef cattle (McDonald et al., 1998; Rego et al., 2008; Krysl et al., 1989; Guthrie et al., 1988). More than 60% of its protein is degraded in the rumen, supporting microbial protein synthesis, while the fraction that escapes degradation can provide amino acids for absorption in the small intestine (INRA, 1988). Soybean meal also has a good amino acid balance and high cell wall digestibility (INRA, 1988). Studies have reported increased feed intake, milk yield or milk protein content in dairy cows (McDonald et al., 1998; Rego et al., 2008), and increased forage intake or nutrient digestibility in steers fed prairie diets (Krysl et al., 1989; Guthrie et al., 1988).
Responses depend on the basal ration and its protein supply: additional soybean meal may not improve production when protein requirements are already met and may increase nitrogen losses (Olmos Colmenero et al., 2006; Keller et al., 2022). Expeller meals retain more oil than solvent extracted meal and generally have higher energy value (Cromwell, 2012; Johnson et al., 2018). In the few trials assessing product quality, soybean meal was not associated with adverse changes in the milk or meat traits measured (Weiss et al., 2015; Menoury et al., 2026; Keller et al., 2021; Saro et al., 2019). Preruminant calves are considered separately because conventional soybean meal is not a straightforward substitute for milk proteins (Ansia et al., 2020; Burakowska et al., 2021).
Because much of soybean meal protein is degraded in the rumen, research has examined heat, mechanical and chemical treatments to increase its rumen undegraded protein (RUP) value and the amount of protein reaching the small intestine (Smith, 1986; Atwal et al., 1995; Wacyk et al., 2000; Chen KuenJaw et al., 2002; Colmenero et al., 2006; Castro et al., 2008).
Dairy cattle
Types of soybean meal and feeding value
Soybean meal can support milk production when it corrects a protein limitation in the ration (McDonald et al., 1998; Rego et al., 2008).
Conventional soybean meal
In grazing cows receiving maize silage, 1.4 kg soybean meal dry matter (DM)/cow/day, alongside 5.2 kg maize silage DM/cow/day, increased milk protein yield by 0.06 kg/cow/day in summer and autumn (McDonald et al., 1998).
In another grazing study, 6 kg concentrate/day containing 18% conventional soybean meal increased milk yield when grass silage was also fed, but not when cows grazed pasture alone; in the latter situation, soybean meal increased dietary nitrogen and feed cost without improving production (Rego et al., 2008).
In total mixed rations based on grass silage, increasing soybean meal from 5% to 10% or 15% of dietary DM formed part of a broader increase in crude protein. Milk and milk protein yields increased with dietary crude protein, but nitrogen use efficiency declined; responses were greater with treated canola meal than with conventional soybean meal (Gidlund et al., 2015).
More protein was not necessarily beneficial. In diets based on maize silage and supplemented with rumen protected methionine, diets containing 15% crude protein and 15% conventional soybean meal supported about 40 kg milk/cow/day, with lower nitrogen excretion than diets containing 17% crude protein and 19% soybean meal, without reducing milk or milk component yields (Nursoy et al., 2018).
Likewise, increasing solvent extracted soybean meal from 9.6% to 11.7% of dietary DM, alongside an increase in crude protein from 16.6% to 17.6%, did not increase milk yield and increased urinary nitrogen excretion by 54 g/day (Olmos Colmenero et al., 2006).
These studies show that soybean meal is a useful protein source, but not that it is always superior to other ingredients or that removing it necessarily reduces production (Doreau et al., 2014; Keller et al., 2022).
A ration containing 15% conventional soybean meal and 15% beet pulp produced more milk than one containing 30% dehydrated lucerne (26.0 vs. 24.1 kg/day); this comparison involved different ingredient combinations and does not isolate the effect of soybean meal (Doreau et al., 2014).
Expeller soybean meal
Expellers retain more oil than solvent extracted soybean meal and may provide more energy (Cromwell, 2012; Johnson et al., 2018).
However, a diet containing 4.6% solvent extracted and 5.9% expeller soybean meal did not sustain milk production as well as one containing 9.6% solvent extracted meal (Olmos Colmenero et al., 2006). Extruded soybean meal at 12% of dietary DM did not improve overall lactational performance and reduced milk protein yield (Harper et al., 2019).
Other soybean meals
In mid lactation cows, milk yields were similar with a diet containing 15.9% conventional soybean meal and diets containing either 11.2% conventional plus 4.4% heat treated soybean meal, or 11.6% conventional soybean meal plus 5.34% high protein distillers’ grains; all percentages are of dietary DM (Chesini et al., 2023).
In diets containing 16% conventional soybean meal, partly or fully replacing hexane extracted meal with 2 methyloxolane extracted meal did not change milk production or nitrogen utilisation (Menoury et al., 2025; Menoury et al., 2026).
Inclusion levels
The dairy cow trials cited here tested conventional soybean meal at 5–19% of dietary DM (Gidlund et al., 2015; Nursoy et al., 2018; Olmos Colmenero et al., 2006). Other studies used 15% of dietary DM with beet pulp (Doreau et al., 2014), 18% of a concentrate fed at 6 kg/day (Rego et al., 2008), or 1.4 kg DM/cow/day (McDonald et al., 1998). An earlier practical reference reported about 35% for dairy cows, above the levels tested in several recent studies (Ewing, 1997).
Beef cattle
Types of soybean meal and feeding value
Conventional soybean meal
Soybean meal can improve forage utilisation when protein is limiting. In Oklahoma, increasing soybean meal from 0 to 603 g DM/head/day increased forage intake and digestibility in heifers fed early cut prairie hay (Guthrie et al., 1988).
In New Mexico, 0.5 kg DM/head/day did not increase forage intake in steers grazing blue grama rangeland, but increased total tract organic matter and nitrogen digestibility (Krysl et al., 1989).
Its value also depends on the protein already supplied by the ration. In a forage based finishing diet that provided adequate metabolisable protein, omitting the additional protein supplement reduced urinary nitrogen excretion without affecting nitrogen or energy utilisation; methane emissions were similar to those from the conventional soybean meal diet (Keller et al., 2022).
Cold pressed soybean cake
Mechanically extracted cake retains more oil than solvent extracted soybean meal, so its energy value and feeding response depend on processing (Chipa et al., 2010).
In South Africa, young Nguni cattle received isonitrogenous feedlot diets containing 0%, 6%, 13% or 20% cold pressed soybean cake. Growth responses were best at 6–13%; 20% provided no additional benefit (Chipa et al., 2010).
Inclusion levels
In growing and finishing beef cattle diets, conventional soybean meal was included at 5.5–6.5% of dietary DM (Keller et al., 2021; Basiel et al., 2024). The 6.5% level was used in a maize based U.S. feedlot diet for beef × Holstein steers (Basiel et al., 2024).
In a 139 day U.S. feedlot trial, soybean meal replaced 50% or 100% of dried distillers grains with solubles initially included at 20% of dietary DM, corresponding to about 10% or 20% soybean meal. Full replacement increased final body weight but was associated with more severe liver abscesses (Ross et al., 2024). An earlier practical reference reported about 35% for beef cattle (Ewing, 1997).
Calves
Types of soybean meal and feeding value
Conventional soybean meal
Conventional soybean meal is a common protein source in solid calf starters and after weaning. In young calves receiving diets based on maize and soybean meal, methionine was identified as the first limiting amino acid, followed by lysine; responses to amino acid supplementation were less evident in older calves (Abe et al., 1998; Abe et al., 1999).
Conventional soybean meal is not a straightforward substitute for milk proteins in liquid feeds for preruminant calves. Residual trypsin inhibitors and antigenic proteins in inadequately treated soybean products can impair intestinal digestion and health (Ansia et al., 2020; Burakowska et al., 2021).
Fermented soybean meal
Fermentation can reduce antinutritional and antigenic constituents of soybean meal (Heuzé et al., 2025). In a Korean experiment, fermented soybean meal in starter feed increased body weight gain at four weeks (0.54 vs. 0.30 kg/day) and preweaning starter intake, although the advantage was not consistent at every age (Kim et al., 2012).
In a 9 week trial in Holstein calves reared in cold weather and abruptly weaned at 59 days, replacing one third or one half of the starter’s 27% conventional soybean meal with fermented meal (9% or 13.5% of starter DM) increased overall average daily gain (719 and 797 vs. 626 g/day). Feed intake and feed efficiency did not differ over the full trial, although both were higher in the fermented meal groups during the post weaning week (Rezazadeh et al., 2019).
Inclusion levels
A practical reference for calf concentrates is approximately 20% toasted soybean meal (Ewing, 1997). In trials with Holstein calves, conventional soybean meal accounted for 23% of starter DM or 24% of starter feed on an as fed basis (Senevirathne et al., 2017; Burakowska et al., 2021).
Sheep
Types of soybean meal and feeding value
Conventional soybean meal
Conventional soybean meal is used in supplementary concentrates for housed and grazing sheep during pregnancy, lactation and rapid growth. Its value depends on forage quality and animal requirements.
In Irish ewes, about 200 g/head/day in pregnancy diets based on maize silage improved ewe intake, weight and condition at lambing, increased lamb birth weight and reduced age at slaughter. Reducing soybean meal in high quality grass silage diets did not impair performance (Keady et al., 2021).
In Jordan, adding 125 or 250 g/day of conventional soybean meal to a low quality forage diet changed daily gain in Awassi lambs from −67 g/day without supplementation to 59 and 96 g/day, respectively; the two supplemented groups did not differ significantly (Obeidat et al., 2020).
In Spain, heavy Assaf lambs fed indoor finishing diets received 5.8–11.5% soybean meal as dietary crude protein increased from 13.4% to 17.3% of DM; daily gain increased from 221 to 297 g/day (Saro et al., 2020).
Inclusion levels
Across the trials reviewed, conventional soybean meal supply ranged from about 73 to 250 g/head/day in lambs and 179–200 g/head/day in ewes (Saro et al., 2020; Obeidat et al., 2020; Keady et al., 2021). Older practical guidance reported soybean meal at about 30% of dietary DM for ewes and 20% of dietary DM for lambs (Ewing, 1997).
Goats
Types of soybean meal and feeding value
Protein requirements in goats vary with physiological stage and production level; they are not uniformly low. Conventional soybean meal can supplement a ration when its protein supply is insufficient, with its contribution assessed against the animals’ needs and the whole diet (Sahlu et al., 2004).
Conventional soybean meal
In Italian dairy goats, replacing 250 g conventional soybean meal/head/day with the same amount of ground maize reduced dietary crude protein from 16% to 12.2% of DM. Milk yield and composition did not differ significantly, while nitrogen use efficiency increased from 28.0% to 37.2% and milk urea decreased (Rapetti et al., 2020).
In growing male Anhui white goat kids in China, a diet containing 20% conventional soybean meal on an as fed basis and 13.4% crude protein on a DM basis maintained growth, whereas a diet containing 16% soybean meal and 12.0% crude protein reduced growth performance. Soybean meal inclusion and dietary crude protein changed together in this comparison (Zhu et al., 2020).
Inclusion levels
The cited trials used 250 g conventional soybean meal/head/day in Italian dairy goats and 20% of complete feed on an as fed basis in growing male kids (Rapetti et al., 2020; Zhu et al., 2020).
