The objective of this study was to investigate the effect of a partial substitution of soybean meal with field pea -Pisum sativum- in Holstein lactating dairy cow diets on dry matter intake, milk yield and composition, blood metabolites, rumen ammonia-N concentration and pH. Eighteen lactating Holstein cows were ran-domly assigned into three groups based on parity, days in milk, and milk yield. Flaked field peas replaced soybean meal -SBM- at the levels of 0.0, 33 and 66% -P0, P33 and P66, respectively- and were fed to the animals for 33 days. Dry matter intake, milk yield, milk fat and protein content, blood metabolites, rumen ammonia-N concentration and pH were not significantly -P<0.05- affected by the diets. The results of this study demonstrated that field pea could safely replace soybean meal up to 66% in the diet of high-producing dairy cows

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