This study evaluated the effects of
branched-chain amino acids on nitrogen
retention and plasma branched-chain amino
acid concentrations. Five ruminally cannulated
Holstein steers (387 lb) were used in a
5 × 5 Latin square. Steers were limit-fed
soybean hull-based diets twice daily (7.5
lb/day, as fed basis). Energy in the form of
acetate (400 grams/day) was continuously
infused into the rumen. Treatments were
continuous abomasal infusions of 1) 115
grams/day of a mixture of 10 amino acids, 2)
10 amino acid mix with leucine removed, 3)
10 amino acid mix with isoleucine removed,
4) 10 amino acid mix with valine removed,
and 5) 10 amino acid mix with all three
branched-chain amino acids removed. Nitrogen
retention decreased (P<0.06) in response
to removal of leucine, valine, or all three
branched-chain amino acids. Changes in
nitrogen balance of growing cattle limit-fed
soybean hull-based diets demonstrate limitations
in the basal supply of leucine and
valine, but not isoleucine.
