Abstract. This experiment was conducted in order to evaluate the effect of undegradable
dietary protein (UDP) level on milk production and composition of 24 lactating dairy cows.
Treatments consisted of T0: ) control diet without UDP (forage and concentrate were offered in
total mixed ration); T1: control diet without UDP (forage and concentrate were offered
separately); T2: control diet + UDP 40 gr/L milk + mineral mix; and T3: control diet + UDP 60
gr/L milk + mineral mix. Data were analyzed using analysis of variance (ANOVA) and the
differences between treatment means were examined by duncan multiple range test (DMRT).
The results showed that UDP supplementation significantly (p