Nevostruyeva I. Nitrogen metabolism in rumen and synthesis of milk components in cows at different degradability of dietary protein

Influence of undegradable protein level in cows diets on rumen metabolism and milk precursors formation in first third of lactation has been investigated. Increase in the dairy cows diets part of undegradable protein from 29.7 to 41.2 % by extrusion of rapeseed meal, from 31.7 to 43.9 % by extrusion of soybean meal, and from 28.5 to 39.5 % by extrusion of sunflower cake increased quantity of protein-linked and decreased quantity of free amino acids in the rumen contents and elevated protein input in the duodenum. In the cows fed by extruded feeds the feces and urine nitrogen excretion were lower. Use of extruded high-protein feeds elevated concentration of protein metabolites in the arterial blood plasma and improved usage of amino acids for of milk components synthesis. Increase of undegradable protein consumption by extrusion of rapeseed meal, soybean meal, and sunflower cake increased average daily yields to 8.9, 15.2 and 13.8 % respectively.