Essential amino acids and their need by lactating cows
Metabolic protein is the main source of truly absorbed amino acids. The determination of metabolic protein and metabolic acids is an important, but very difficult task. To do this, you need to know the exact number of incoming protein fractions in the small intestine as part of the duodenal fl ow of chymus, their digestibility, the fl ow of metabolism of essential amino acids from the intestine to the bloodstream and the coefficients of their use for milk protein biosynthesis and maintenance of life. The purpose of the research was to determine the need of lactating cows for metabolic essential amino acids by factorial method. During the researches, developed standards needs to metabolic essential amino acids for lactating cows (g/kg) milk with a content of 3,3 % (33 g/kg) crude protein and 3,15 % (31,5 g/kg) of pure protein and to maintain 1 kg/body weight 0,75, which allows to calculate the daily requirement in the absolute number of amino acids (g). The assessment of security of rations of lactating cows metabolic lysine and methionine has been shown coincidence with the norms of needs in the amount of 93 %; daily milk yield of natural milk under this provision of lysine and methionine were 38,7 % and 39,4. The availability of metabolic methionine was at the level of 77-85 %, which is explained by the unprocessed coefficients of transformation of metabolic methionine into pure methionine of milk protein. In the total duodenal fl ow of amino acids approximately 60-70 % is microbial protein and 30-40 % is non-degradable protein in the rumen. It has been found that the digestibility of dry and organic matter in the rumen and the general digestive tract in relation to UDP:DP 35: 65 % crude protein is 2-3 % (absolute) higher than for UDP:DP = 50:50 % crude protein.