Five isonitrogeneous and isocaloric feeds containing various levels of palm kernel cake (0, 10, 20, 30 and 40%) as a replacement for fishmeal were fed to four replicate groups of sex-reversed red tilapia (Oreochromis niloticus Linn.) fingerlings, mean initial weight 3.02-3.03 g, in 235-l aquaria fitted with a closed recirculation system for 10 weeks. The results showed declines in growth, feed utilization and digestibility coefficient with increases in the levels of supplemented palm kernel cake. The maximum growth was achieved in the fish given the feed with 10% palm kernel cake and was different from that when the basal feed (formula 1) was used. Satisfactory results of feed utilization, (feed conversion ratio, protein efficiency ratio, apparent net protein utilization) and digestibility coefficient were noted in the fish groups given the feed with a maximum of 20% palm kernel cake in their feeds. The supplementation of palm kernel cake at any levels in the feeds had no effects on fish’s blood parameters or hepatosomatic index. It was concluded that the maximum of 20% palm kernel cake could be supplemented in the feed for sex-reversed red tilapia while maintaining satisfactory growth, feed utilization, digestibility coefficient and normal fish physiology. Besides, the feed cost was kept minimum compared to the supplementation of other levels of palm kernel cake in their feeds.
