Abstract
The objective of this study was to investigate the effect of various concentrations of olive cake (OC) with or without supplementation of different concentrations of citric acids (CA) on the growth performance, utilisation, blood components, carcass and meat physical traits of the commercial broiler chickens. A total of 360 Ross-308 male broiler chickens at 28 day of age were distributed randomly among 9 treatments (40 chickens/treatment), with 8 replicates per treatment and five chickens in each replicate, during the experimental period from 28 to 49 days of age. The experimental design was a three by three factorial. The OC was supplemented at 0, 10 and 20% in isocaloric, isonitrogenous diets that were fed with or without 1 or 2 g/kg citric acid.
The results demonstrated that OC could be included in broiler diets up to 10% without CA supplementation. However, CA supplementation to the 20% diet increased growth and resulted in a feed conversion ratio and European production efficiency index score similar to that of the control diet. OC and/or CA had no negative effects on hepatocellular markers and meat physical characteristics. These results suggest that OC can be fed to broiler chickens during 28 to 49 days of age at 10% without CA supplementation, and can be increased to 20% when supplemented with 1 g/kg CA without adverse effects on feed conversion and health status of the broilers. Also, further studies are required to investigate the possibility of using higher percentages of OC with different feed additives to enhance the utilisation of OC in broiler diets. The positive impact on the environment from using this by-product should also be considered.