Performance and milk composition of dairy goats as affected by the dietary level of stoned olive cake silages

Objective: The current study compared the effects of dietary levels of two phase stoned olive cake (OC) in form of silage (OCS) on milk production and quality of Saanen goats. Methods: The OCS included in total mixed ration (TMR) at dry matter proportions of 0.0 (OC0), 0.10 (OC10), and 0.20 (OC20). The TMR were fed to a total of 18 goats in a completely randomized design for a period of 5 weeks. Results: Dietary treatments had no effect on the milk yield of Saanen goats, but the daily milk fat production was greater (p<0.05) at feeding OC20. The total phenolic (TP) compounds contents increased (p<0.01) in each increment of OCS in TMR and this was also reflected in the TP contents of milk. The C8:0, C10:0, C12:0, and C14:0 saturated fatty acids (FAs) in milk fat decreased (p<0.01) with increasing dietary level of OCS, but the decrease (p<0.001) in C16:0 and the increase (p<0.01) in C18:0 in milk fat occurred similarly at each inclusion level of OCS. Only OC20 reduced (p<0.05) the total saturated FA, yet the reduction (p<0.01) in n6/n3 ratio and atherogenicity index occurred in both OC10 and OC20. Conclusion: Two phase stoned OCS increases milk quality not only through modifying the milk FA composition, but also by increasing the milk TP content. These favorable changes in milk quality are closely associated with the dietary level of OCS.