Prediction of Individual Amino Acid Passage to the Small Intestine of Dairy Cows from Characteristics of the Feed

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Abstract
Passage of individual amino acids (AA) to the small intestine of dairy cows was measured in 33 periods with 2–5 cows in each period. The diets covered a wide range of different feedstuffs. The content of individual AA and feed protein degradability using the nylon bag technique was measured on each feedstuff. The measured duodenal flow of each individual AA was related to parameters measured on the feed using 3 different equations including different sources of information concerning microbial protein synthesis and undegraded feed protein. All 3 equations predicted the flow of individual AA to the duodenum with approximately the same precision resulting in R square values mostly higher than 0.9 and a coefficient of variation between 10 and 15%. Including more detailed information in the equation such as AA composition of feed protein failed to improve the precision of predicting the flow of individual AA to the duodenum, over and above what could be predicted solely from the amount of totally digested carbohydrates and the amount of undegraded dietary nitrogen in a diet.