Impacts of dietary metabolizable protein on performance and ruminal parameters of Holstein cows at early lactation

The effects of different levels of metabolizable protein (MP) on production efficiency and ruminal parameters of early post-partum dairy cows were examined. Forty-two multiparous and 16 primiparous Holstein cows were assigned to 3 diet treatments in a completely randomized block design immediately after parturition. . Diets were formulated to provide three concentrations of dietary MP [Low MP, 1893; Medium MP, 2023; and High MP, 2149 g/day of dry matter (DM)] while rumen-degraded protein (RDP) remained constant (11.3% of DM). Dry matter intake was linearly increased by treatment. Whole milk yield, fat corrected milk and protein content increased significantly when increasing MP content in the diet fed to cows. Digestibilities of DM and CP increased significantly with the increase of MP. Ruminal concentrations of acetate, propionate and butyrate and total Volatile fatty acidss were increased significantly (P<0.05) by the increase of dietary MP, however the rumen pH did not differ among treatments. Generally it can be concluded that, increasing the level of MP in the diet of cows at early lactation improved the productive performance of the cows as well as their rumen function and digestibility of feeds.