In this study, 73 non-pregnant and clinically healthy and lactating Holstein cows without any clinical signs, and with a mean parity of 3.2 ± 1.4, days in milk at the beginning of study 110 ± 20 days, body condition score (BCS) of about 3.2 ± 0.3, and milk production rate of 48± 10 kg were selected and randomly placed in two treatment and control groups. In the treatment group (n=36), arginine (155 μmol / kg body weight) was injected once every 8 hours a day for 6 days, and in the control group (n=37) saline solution (0.11 ml/kg body weight, once every 8 hours a day) was injected for 6 days. The results showed that there was no difference between the treatment and the control group in terms of milk production (38.5 and 36 kg, P=0.3), fat (3.7 and 3.8%, P=0.8) and protein (3.1 and 3.1%, P=0.5) levels. It was concluded from this study that the use of arginine after the peak of milk production could not increase the fat, protein, and production levels of milk.

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