The objectives of this study was to investigate whether consuming of protected glutamine (PG) before parturition in close up period would affect dry matter intake (DMIkg/d), blood urea nitrogen (BUNmg/dl), body condition score (BCS) and biomarkers of oxidative stress, glutathione peroxidase activity (GPX units/ml PCV) and Total Antioxidant Status (TASmmol/L). Thirty six pregnant Holstein dairy cows were assigned into two treatment groups based on their BCS and expected calving date in t student examination. Treatment groups consisted of 1)glutamine supplementat - ion100 g/d per cow from 21d before calving until parturition (F), 2) glutamine unsupplementation from 21d before calving until parturition (N). There weren’t any significant differences among treatments in DMI and BCS on d -21,-14 ,-7 and calving day before parturition. There weren’t significant differences in The total antioxidant status(TAS) but plasma glutathione Peroxidase activity (GPX) was significant difference between two group and was greater for (F) group at -7d before calving (57.44 vs 47.94 and p≤0.05 respectively) and -14 (45.87 vs 41.72 and p≤0.04 respectively) before parturition. It seems that supplementation diets with glutamine on the close up period can enhance plasma glutathione Peroxides activity (GPX) and the best level of formaldehyde for protection of glutamine is 1%.
