EFFECT OF DIETARY PROLINE SUPPLY ON N-BAL ANCE OF PIGLETS .3. COMMUNICATION ON THE IMPORTANCE ON THE IMPORTANCE OF NONESSENTIAL AMINO-ACIDSFOR PROTEIN RETENTION

In a metabolism trial with 6x4 piglets of 15 kg live weight, the effec t of L-proline additions to a proline-free chemically defined amino ac id diet on N-balance was studied. Proline was added to the N and energ y-equivalent diets at 0, 0.35, 0.7, 1.05, 1.4, and 2.1%. All diet grou ps contained 0,48% L-arginine and 2,0% L-glutamic acid in order to mee t the pigs' requirement of these amino acids. Increasing poline supply improved daily growth rate from 342 g to 411 g and feed conversion ra ce from 1.66 g to 1.35 g feed/g gain. Dietary proline levels of 1.4% a nd 2.1% maximized daily N retention from 1.27 to 1.53 g/kg LW(0,75). N utilization thereby increased from 64% to a maximum of 73%, and the b iological value of the diets from 73% to 83%. Increasing dietary proli ne levels showed linearly elevated plasma proline contents, while the plasma urea content was reduced by half. The results indicated that yo ung pigs cannot synthesize proline sufficiently for maximum N utilizat ion and N retention. For these parameters, dietary proline levels of 0 .7 and 1.4% are required.