A study was conducted to determine the
limiting amino acids for cattle fed soybean hullbased
diets. Ruminally cannulated Holstein
steers (335 lb) were maintained in metabolism
crates, fed the same basal diet (73% soyhulls,
19% alfalfa), and given the same intraruminal
infusions (400 g/day acetate to increase energy
supply without increasing microbial protein
supply). Steers were infused into the abomasum
with a complete mixture of the 10 essential
amino acids or the mixture with histidine;
tryptophan; arginine; phenylalanine; or the three
branched-chain amino acids (leucine, isoleucine,
and valine) removed. Nitrogen retention was
reduced by removal of either histidine or the
branched-chain amino acids, suggesting that
those amino acids were limiting.
