EFFECTS OF ADDING NONESSENTIAL AMINO-ACIDS TO LOW-PROTEIN DIETS FOR GROWING PIGS ON N BALANCE .3. COMMUNICATION ON BALANCE STUDIES TO REDUCE N EXCRETION

In the first of two trials based on 7 x 4 N balances with growing pigs the biological efficiency of different supplements of L-glutamic acid + L-aspartic acid + L-alanine (NEAA) in the proportions 1.5:1:1 was investigated in comparison with N equivalent native protein diets. The protein contents of the 7 diets including the NEAA-supplements (given in brackets) had been each as g/kg: 100(+0), 125(+36), 150(+72), 125(+0), 137.5(+18), 150(+36) and 150(+0). In the second N balance trial with 14 pigs the diets 100(+0) and 150(+72) were buffered with 20 g/kg KHCO3 and the diet 150(+72) was delivered in a further group in 5 meals per day. Pure essential amino acid were added to meet the requirement in all diets. In trial 1 increasing native protein contents from 100 to 150 g/kg improved N retention and N utilization linearly. Adding of NEAA showed only at the protein level of 125 and 137.5 g/kg the same N balance as the native protein source. Increasing the protein level from 100 to 150 g/kg or from 125 g to 150 g/kg by NEAA supplements reduced N balance, N utilization and biological value significantly in comparison with the native protein level of 150(+0). Free amino acids and urea of the blood plasma were influenced by protein level and supplementation of NEAA. Low protein diets and intake of NEAA resulted in a extremely high urinary NH4+ excretion. In the second trial the lowered efficiency of NEAA was abolished by KHCO3. Meal frequency was without effect on N balance. Urinary NH4+ excretion was markedly diminished in all groups. The low efficiency of the supplemented NEAA was discussed in connection with an unsufficient transamination and an increased acid load caused by the used low protein basal diet.