USE OF A CHEMICALLY-DEFINED AMINO-ACID DIET IN A N-BALANCE EXPERIMENT WITH PIGLETS .1. COMMUNICATION ON THE IMPORTANCE OF NONESSENTIAL AMINO-ACIDS FOR PROTEIN RETENTION

In a balance experiment with piglets of 10-15 kg live weight, a chemically defined amino-acid diet was compared to a commonly used diet with regard to growth and N retention. The amino-acid diet contained essential amino acids as recommended by CHUNG and BAKER (1991) and a complete mixture of non-essential amino acids (alanine, aspartic acid, glutamic acid, glycine, proline, serine). The commonly used diet was based on grain, soy bean meal, fish meal and skim milk powder. In both diets, 15.6 and 19.8 % crude protein, respectively, and 15.6 and 13.0 MJ ME/kg, respectively, were estimated. At similar energy-intake levels, growth rate was 24 % lower and energy expenditure 26 % higher as a result of feeding the amino-acid diet rather than the common diet. The amino-acid diet resulted in a 14 % lower absolute N retention but the percentage N utilization increased by 15 %-units. The apparent N digestibility of the amino-acid diet and the common diet was 94.4 % and 78.8 %, respectively. Both diets showed a similar biological value of the respective proteins of 87,8 % and 83,5 %. It was concluded chat, in order to increase growth rate and N retention, the amount of dispensable amino acids in the chemically defined diet should be raised and the pattern of indispensable amino acids should be further improved in order to attain an ideal protein.