The use of a by-product of the recently developed two-stage centrifugation process to extract olive oil, the dry and extracted two-stage olive cake (TSOC), in goats and sheep feeding is studied. Samples of TSOC were treated with PEG 4000 MW (0, 20, 60, 100 and 200 g per 100 g by-product). The addition of PEG significantly modified the CP and the N-ADF contents (P less than 0.05 and P less than 0.01, respectively). The IVOMD, increased significantly (P less than 0.05) when 100 g of PEG per 100 g by-product was added. The extent and rate of rumen degradation of CP were determined using the in sacco procedure, in goats and wethers. The effective rumen degradability and the rate of degradation significantly (P less than 0.05) increased with the addition of more than 20 g of PEG per 100 g by-product either in goats and wethers.