Influence of sarsaponin on growth, feed and nitrogen utilization in growing male rats fed diets with added urea or protein.

Two experiments were conducted with growing male rats to determine the effects of 120 ppm of dietary sarsaponin (S) on nitrogen (N) metabolism when urea or protein are added to the diet. Growth, feed efficiency, N digestibility and balance, urinary N and ammonia-N (NH3-N), and cecal urease and NH3-N were measured. Growth and feed utilization were unaffected by dietary S. Adding urea or protein to the diet increased apparent N digestibility and increased urinary-N excretion. Urea did not affect N balance, whereas growth, feed utilization and N balance were maximized with 22% compared with either 16 or 28% dietary protein. Urinary NH3-N excretion was decreased by S when urea was added to the diet but was not affected when fed with increasing dietary protein. Cecal urease was decreased by S when urea was added or when the protein level was increased in the diet; effects on cecal NH3-N varied between the two experiments. Plasma urea-N was decreased by S. It is concluded that S has minor effects on N metabolism in rats and that NH3-N formation or excretion is only marginally affected by dietary S. If S decreases NH3-N level in confinement facilities, it is concluded that the effect is after the waste material is excreted by the animal, perhaps through reduced urease activity.