What question did this study set out to answer?

The study aimed to assess the impact of dietary crude protein adjustments on milk yield and nitrogen efficiency in Holstein lactating cows.

March 21, 2026Open Access

Dietary replacement of soybean meal with heat-treated fermented soybean meal on milk production and nitrogen efficiency in lactating dairy cows

Key Points

The study aimed to assess the impact of dietary crude protein adjustments on milk yield and nitrogen efficiency in Holstein lactating cows.
13 Holstein cows were divided into two dietary groups: soybean meal (SBM) and heat-treated fermented soybean meal (HFSBM).
Cows were stratified by days in milk, parity, and milk yield, using a completely randomized design.
Various parameters including milk production, ruminal ammonia, and blood urea nitrogen levels were measured.
No significant differences were observed in overall milk production or composition between the SBM and HFSBM diets.
Ruminal ammonia concentrations were lower in the HFSBM group, indicating improved nitrogen utilization.
Total protein levels in blood were higher with the HFSBM diet, and nitrogen efficiency tended to increase.

Abstract

Objective:We investigated the effect of reducing dietary crude protein (CP) and rumen degradable protein (RDP) while increasing rumen undegradable protein (RUP) on milk yield and composition, nitrogen (N) metabolism, and rumen and blood parameters in Holstein lactating cows.Methods: Holstein cows (n = 13) were stratified by days in milk (91.75 32.39), parity (2.58 1.44), and milk yield (42.86 kg 6.6), and randomly assigned to one of two dietary groups (soybean meal (SBM) or heat-treated fermented soybean meal (HFSBM) group) in a completely randomized design.Results: There were no differences in dry matter intake, milk production, milk composition (fat, protein, lactose, somatic cell count, -hydroxybutyrate, and milk urea nitrogen).Ruminal ammonia concentrations were lower in the HFSBM group than in the SBM group.Ruminal total volatile fatty acid concentrations, acetate and propionate proportions, and blood urea nitrogen concentrations, did not differ.Calcium levels in the blood were lower both before feeding (0 h) and 3 h post-feeding in the HFSBM group compared to the SBM group.Total protein levels in blood were higher in the HFSBM group.There were no differences in digestibility of dry matter (DM) or CP, NDF.N outputs from feces and urine did not differ.Nitrogen efficiency tended to be higher in the HFSBM group. Conclusion:Replacing SBM with HFSBM did not affect milk production but reduced ruminal ammonia concentrations, indicating that reducing dietary CP by increasing RUP levels can be implemented in dairy production without negatively impacting cow performance.

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