ABSTRACT
This study conducted to evaluate the influence of Ziziphus spina-christi leaves (ZSCL) as natural growth promoter and monensin as a synthetic growth promoter when both were supplemented into the basal diet that consisted of 40% berseem hay and 60% concentrate feed mixture (CFM) which served as control ration (R1). Tested rations consisted of control ration supplemented with 30 mg monensin (R2) or 15 g ZSCL (R3), per Kg DM intake. Nine Ossimi rams averaged 65±2.7 kg live body weight, 16-18 months old divided into 3 groups (3 animals each) according to live body weight for nutrients digestibility and dietary nitrogen utilization. Three Ossimi rams with rumen fistulae per treatment were used for rumen fermentation activity and total gas production. Twenty-one Rahmani lambs averaged 24±0.48 kg body weight and 4 months old divided into 3 groups (7 animals each) according to live weight for 120 days to investigate the growth performance of growing lambs fed the experimental rations. Results revealed no differences among the rations (P>0.05) in daily feed intake. Also, no effect was observed on digestibility of DM, EE and NFE among the experimental rations, while, digestibility of OM and CP in R2 ration were significantly (P<0.05) higher than R1 (control group), but similar to R3 ration. The rumen pH at 4 hrs after feeding did not significantly affected by rations. Total VFA concentration was significantly lower (P<0.05) with R2 ration compared with R1 and R3 rations. Ammonia-N, concentration also followed the same trend of TVFA'S among the experimental rations. Total gas production reduced (P<0.05) for R2 and R3 on incubation times; 24 hrs by (38.96 and 14.44%, respectively) and 48 hrs by (28.19 and 10.16 %, respectively), whilst, at 72 hrs time of incubation, total gas production significantly reduced (P<0.05) with R2 ration than R1 and R3 while no significant differences found between the two latter ones. Values of final weight and total gain of R2 were significant higher (P<0.05) than those of R1, but insignificant higher than R3. While, daily gain of R2 was significantly higher than R3. Therefore, the use of either monensin or ZSCL (15 g /kg DM) is highly recommended in the feeding practices of growing lambs as feed additives.