THE EFFECT OF DIETARY ARGININE SUPPLY ON THE N-BALANCE OF PIGLETS .4.COMMUNICATION ON THE IMPORTANCE OF NONESSENTIAL AMINO-ACIDS FOR PROTEIN RETENTION

In a metabolism trial with 6 x 4 piglets of 15 kg live weight, the eff ect of L-arginine additions to an arginine-free amino-acid diet on N b alance was studied. Arginine was added to the N- and energy-equivalent diets at 0, 0.3, 0.4, 0.5, 0.6, and 1 %. All diet groups contained 1. 4 % L-lysine, 2 % L-glutamic acid and 1.4% L-proline in order to meet the requirement of these amino acids. N balance was measured for a wee k after 2 weeks diet adaptation. Increasing arginine supply up to 0.5 % improved daily growth rate from 30 to 365 g, daily feed intake from 224 to 494 g, and feed-conversion rate from 7.46 to 1.35 g feed/g gain . Dietary arginine level of 0.5 % maximized daily N retention from 0.5 9 to 1.46 g/kg LW(0.75). N utilization thereby increased from 59 to 74 % and biological protein value of the diets from 76 to 83 %. Arginine levels above 0.5 % did not further improve these mentioned parameters . Plasma urea was decreased by 50 % at 0.5 % dietary arginine. At the same time, plasma arginine increased linearly from a very low starting level. Renal excretion of erotic acid and ammonia were not dependent on arginine intake. From the data, it was calculated that piglets coul d only synthesize 40 % of the arginine retained in the tissue protein al an arginine supply that just met the requirement. Urea synthesis wa s not affected by the arginine free diet. Urinary erotic acid was not suitable for indicating the arginine status. The arginine requirement was estimated at a dietary content of 0.55 %.