24 Comisana ewes were fed on subterranean clover (SC, phytoestrogen content = 0.794 mg/g of DM) or Italian ryegrass (IR) for one year to verify the effects of a prolonged ingestion of phytoestrogens on growth rate and reproduction. The animal initial weights were: SC=25.3 kg ± 2.99 and IR=24.7 kg ± 3.83, respectively. Differences on growth became evident after one month of feeding; after 170 days ewe weights were 47.5±3.43 vs 41.1±4.35 kg (P≤0.01) and ADG was 145.5 g/d vs 107.2 g/d (P≤0.001). No differences were recorded on the onset of puberty and on lamb births: 14 for SC group (LW=4.83 kg) and 15 for IR (4.36 kg).