The current study was carried out to investigate the effect of Long-term betaine supplementation on performance of Saidi lambs during growing period. Twenty-four local Egyptian lambs (Saidi) with 7 months of age and average body weight of 25 ±1.36 kg were used. Lambs were allocated to one of the three experimental treatments of eight replicates (control group, low betaine supplementation (LBS); supplemented with 1500 mg betaine /kg concentrate mixture or high betaine supplementation (HBS); supplemented with 2500 mg betaine /kg concentrate mixture) at RCBD design. Concentrate mixture was fed to cover 80% of the daily requirements while the other 20% was supplied by offering wheat straw ad libtum.