The speciation of lysine-complexed copper as a bovine nutritional supplement

Copper deficiencies in ruminants can be corrected by administering either free (inorganic) or complexed (chelated) copper. Chelated forms are thought to be more bioavailable as they are more stable, and may therefore be absorbed intact. Formation constants for the complexes between copper and the different ligands in the digestive tract can be used to predict if the chelate does, in fact, remain intact. Using a gravimetric autotitrator, the various complex formation constants for the copper(II) lysine system were determined at 38 degrees C, the temperature of the rumen environment. Formation constants for copper(II) complexes with the amino acids glycine and histidine were also determined at 25 and 38 degrees C. The formation constants for the copper(II) lysine system were then utilized in computer simulations to determine the fate of the complex prior to arriving at the rumen. The speciation of the copper(II) lysine system was determined in McDougall's solution, a simulated form of bovine saliva. Results suggest that if copper is administered as copper lysine "chelate," this will disintegrate and the copper will be present mainly as carbonate and phosphate complexes.