Mixed feeding schedules in semi-intensive pond culture of Nile tilapia, Oreochromis niloticus, L.: is it necessary to have two diets of differing protein contents?

摘要

Two semi-intensive grow-out trials of Nile tilapia, Oreochromis niloticus (L.), each consisting of seven mixed feeding schedules (rhythmic presentation of high and low protein) and two constant, a high-protein and the other low-protein feeding schedules, were carried out simultaneously for 60 days. Mixed feeding schedules were achieved, in Trial 1, by alternating the presentation of a high feed ration (H; 2.3% body weight (BW)) with a low feed ration (L; 1.5% BW) of a single diet A (crude protein content 33%), and in Trial 2, by alternating the presentation of diet A with diet B of a relatively low protein content (crude protein content 22%). In both trials, significant improvements in protein utilization parameters, such as apparent protein conversion efficiency and protein efficiency ratio against continuously high protein feeding were obtained because of the adoption of mixed feeding schedules without any significant decline in the growth parameters such as net fish yield or daily weight gain. In both trials, the mixed feeding schedule ensuring 2 days of high followed by 3 days of low protein presentation, viz. 2H/3L, of Trial 1 and 2A/3B of Trial 2 performed the best. Improvement in nutrient utilization in both trials was comparable; however, at existing market prices cost saving because of adoption of mixed feeding schedules was greater in Trial 1.