EFFECTS OF FEEDING YUCCA-SCHIDIGERA EXTRACT IN DIETS VARYING IN CRUDEPROTEIN AND UREA CONTENTS ON GROWTH-PERFORMANCE AND CECUM AND BLOOD UREA AND AMMONIA CONCENTRATIONS OF RABBITS

Yucca extract (YE) has ammonia-binding properties, It was hypothesized that by binding ammonia in the cecum, YE could influence cecal utiliz ation of crude protein (CP) and dietary urea. Two experiments were und ertaken using New Zealand White weanling rabbits (5-6 weeks of age). I n both experiments, YE was mixed at 250 mg kg(-1) of diet, and six ind ividually fed rabbits were used per treatment. In Experiment 1, the fo ur diets were: (1) high-protein (HP); (2) HP + YE (HPYE); (3) medium-p rotein (MP); (4) MP + YE (MPYE), The two protein levels were 23% and 1 9%. Average daily gain (ADG) was higher (P < 0.01) in HPYE vs. HP wher eas it was similar in MP vs. MPYE, There was no significant interactio n between CP and YE. Feed intake was similar among treatments. Feed/ga in in HPYE was better than in HP (P < 0.05). Cecal urea-N (CUN), cecal ammonia-N (CAN) and cecal pH did not differ significantly among the f our treatments. Plasma urea-N (PUN) concentrations differed among trea tments (P < 0.01). The PUN differed (P < 0.05) between HP and MP treat ments. The interaction of CP and YE was significant (P < 0.01), The PA N was higher (P < 0.05) for HP than for the other treatments. Cecal pr opionate was lower (P < 0.05) for MP than for HP treatments. In Experi ment 2, diets were: (1) low protein (LP); (2) LP + YE (LPYE); (3) LP urea; (4) LPU + YE (LPUYE), The two CP treatments were 16.5% CP and 1 6.5% CP + 2% urea. The ADG was highest (P < 0.05) for the LPYE, and wa s lower(P < 0.05) for the LPU than for the LP treatments. CUN was simi lar among treatments, whereas CAN was lowest (P < 0.05) in LPUYE. The PUN was higher (P < 0.05) in the LPU than in the LP treatments, and wa s higher for LPU than for LPUYE. There were no differences in PAN. Cec al acetate and propionate concentrations were higher in LPYE than in t he other groups, indicating a favorable effect of YE on cecal fermenta tion. It is concluded that YE modifies the utilization of dietary CP a nd urea by rabbits, by influencing cecal fermentation. This effect is probably mediated by ammonia binding.