Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Jeffery O. Hall


Jeffery O. Hall


Jong-Su Eun


Kerry A. Rood


Allen J. Young


Juan J. Villalba


Dirk K. Vanderwall


Cows have a protein requirement for growth, maintenance, and lactation. In order to meet those protein requirements, dairy farmers can supplement or feed cattle with specific amino acids, the building blocks that make-up protein. However, in order for the amino acid product to be effective it must avoid degradation in the rumen and be delivered in the small intestine for absorption. Lysine and methionine have traditionally been recognized as the most limiting amino acids for lactating dairy cows. Therefore, nutrition companies have focused on finding ways to encapsulate or protect lysine and methionine from rumen microbes. The N-acetyl-L-methionine and N-acetyl-L-lysine are amino acid derivatives and developmental forms of amino acids for dairy cows. Three separate nutrition studies were conducted to investigate the use of lysine and methionine acetylated derivatives as sources of amino acids for lactating dairy cows. The initial study investigated milk production responses of lactating dairy cows when supplemented with N-acetyl-L-methionine. Supplementation of N-acetyl-L-methionine increased milk fat concentration and yield and 3.5% fat-corrected milk yield. Results from the first study suggest that N-acetyl-L-methionine did not impact rumen metabolism, but increased milk fat concentration by providing methyl donors to the mammary gland, resulting in increases in milk fat yield. The second study investigated lactational performance of dairy cows when supplemented with Nε-acetyl-L-lysine, Nα, ε-acetyl-L-lysine, or AjiPro®-L as a source of rumen-protected lysine. Feeding the Nα, ε-acetyl-L-lysine and AjiPro®-L diets decreased dry matter intake. Milk yield was not altered by rumen-protected lysine supplementation. Findings from the study suggest that supplementing Nα, ε-acetyl-L-lysine to dairy cows decreases dry matter intake, but maintained milk yield leading to improved milk production efficiency. The final study evaluated the bio availability and lactational performance of dairy cows supplemented with N-acetyl-L-methionine. Overall, milk production parameters were not affected by N-acetyl-L-methionine supplementation. Bioavailability was higher for diets with N-acetyl-L-methionine compared with the control diet. Residue of N-acetyl-L-methionine was not detected in plasma, milk, liver, or muscle samples. Overall, findings suggest that N-acetyl-L-methionine is deacetylated and absorbed as methionine into the bloodstream of cows, supplying lactating dairy cows with a bioavailable source of rumen-protected methionine.



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