The inclusion of olive cake, even those with high moisture, into multi-nutrient blocks has proved to be a promising way for their utilization, as they may decrease feed costs by 18 to 38 % (Ben Salem et al., 2003; Molina Alcaide et al., 2008).
Overall olive cake degradability was reported to be low (32 % after 72 h) (Nefzaoui, 1991). MS effective degradability was as low as 37 % or 42 % (Álvarez-Rodríguez et al., 2009 ; Molina Alcaide et al., 2008). N effective degradability is also very low (44 %) due to high N-ADF (Nefzaoui, 1991 ; Molina Alcaide et al., 2008). The rumen degradability of amino acids is higher (0.75 and 0.90, respectively) than that of CP (0.45 and 0.56, respectively). Exhausted olive oil cake is even less degradable with MS degradability as low as 12 % (Álvarez-Rodríguez et al., 2009). Nutritive values appear to be higher in crude olive oil cake than in the defatted cake. Crude cake may nevertheless limit the global digestibility of the diet since its high oil content reduces rumen fermentations by increasing fat and free fatty acids content and its high polyphenol and lignin content inhibits fermentation (Álvarez-Rodríguez et al., 2009; Zaidi et al., 2008; Sansoucy et al., 1985).
OM digestibility (OMD) in sheep can be predicted by the following relations (Gomez Cabrera, 2010, personal communication):
– OMD (%) = 104.29 – 1.4 ADF (% DM) (r = -0.88; n = 8; RSD = 4)
– OMD (%) = 89.82 – 1,37 (ADF – N-ADF) (% DM) (r = -0.91; n = 8; RSD = 3)