EFFECT OF ABOMASAL INFUSION OF ASPARTATE ON NITROGEN-BALANCE AND PLASMA AMINO-ACIDS IN HOLSTEIN STEERS

We investigated the effect of abomasally infused aspartate (Asp) on N balance and plasma amino acids in steers. Four ruminally cannulated Ho lstein steers (180 kg) housed in metabolism crates were used in an exp eriment designed as a 4 x 3 Youden square. Steers received continuous abomasal infusions of water or water containing 40 or 80 g Asp/d. Stee rs were fed twice daily a diet containing 473 g/kg corn, 463 g/kg alfa lfa hay and 52 g/kg soybean meal at levels near ad libitum intake. Abo masally infused Asp had no effect on N balance. Infusion of 80 g Asp/d increased (P < 0.05) plasma concentrations of Asp, glutamate and alan ine. Metabolism of Asp by gut tissues probably prevented the large cha nge in plasma concentration of Asp that seems necessary to trigger hor monal responses. We conclude that abomasal supplementation of steers w ith up to 80 g/d of Asp does not enhance performance. (C) Inra/Elsevie r, Paris.