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Abstract

Thirty multiparous Holstein dairy cows with average body weights of 687±15 kg and body condition scores of 3.25±0.15 were allocated to 1 out of each 3 groups, immediately after parturition (DIM=11) and in a completely randomized design. The first group was fed diet low in Rumen Undegradable Protein (RUP; 5.1% of dry matter), the second group fed with medium RUP (7.2% of dry matter) while the third fed with high RUP (9.8% of dry matter). Diets were similar in Net Energy Lactation (NEL) and Rumen Degradable Protein (RDP). Statistical analysis of data obtained on dry matter intake indicated that an increase in RUP would result in greater dry matter intake. Increase in dietary RUP content, increased yield of milk and 4% FCM yield in fresh cows (d 1 to 21). Milk protein content as well as yield and Somatic Cell Count (SCC), and total efficiency were significantly different among experimental diets. Also, increased levels of RUP in the experimental diets increased blood concentrations of glucose, blood urea nitrogen and cholesterol while decreasing non-estrified fatty acids. Compared with the control diet, feeding diets 2 and 3 increased concentrations of total protein, albumin and globulin, while reducing ?-hydroxybutyric acid and aspartate aminotransferase activity, but had no significant effect on estrogen concentration. Change in body condition score differed among experimental diets. Overall, results indicated that the experimental diets with medium RUP (7.2% of dry matter) improved the animal's performance as well as its health.

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