One possible way to reduce urinary nitrogen (N) excretion is reducing the amount of dietary crude protein fed to dairy cows. In fact, decreasing dietary crude protein (CP) concentration from 184 to 151g/kg, linearly decreased urinary N expressed as gram per day or as a percentage of N intake (Broderick, 2003). Balancing diets for limiting amino acids could improve cow responses fed lower protein diets without increasing N losses in urine. High concentrations of methionine and lysine during early lactation may reduce the risk of metabolic disorders (Berthiaume et al., 2006). A number of blood metabolites are useful as monitors for signs of metabolic disorder. The aim of this experiment was to determine the effect of altering the dietary methionine concentration on some blood metabolite concentrations of early lactating Holstein cows.

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