Six ponds were stocked by 1000 of Nile tilapia fingerlings for each pond (4000 fingerlings/feddan). The six ponds assigned into two groups, each group composed of three ponds, the three ponds of each group stocked with 100, 200 and 300 silver carp for the first, second and third pond, respectively. The three ponds of the first group had the first feeding regime (M) (fertilized with 50 kg poultry litter/pond/week) and the three ponds of the second group had the second feeding regime (F)(fish feed containing 30% crude protein).
Tilapia fish fed supplementary feeds compared with fish fed the first feeding treatment (natural food) show higher percentages of dressing (50.3 vs. 47.7%) and flesh (39.2 vs. 37.3%) and lower percentage of head (30.8 vs. 33.3%), viscera (7.1 vs. 7.7%) and by-products (54.5 vs. 56.8%). The differences between these components, due to feeding regime were significant for dressing and head percentages.
The second stocking rate (SR2) had higher percentage of dressing (50.1%) compared with 49.2 and 47.6% for the first (SR1) and third (SR3) stocking rate, respectively. The differences between dressing percentages were significant.
The carcasses of silver carp fish fed the first feeding treatment had higher percentages of by-products (51.3 vs. 49.%) and lower percentages of flesh (48.2 vs. 50.8%) compared with fish fed the supplementary feeding. The three stocking rates had insignificant effect on carcass traits.
Tilapia flesh of the first treatment (M)compared with the flesh from fish fed supplementary feed, had higher and significant percentages of protein (87.02 vs. 84.00%) and ash (7.54 vs. 6.23%) but lower percentages of fat (6.12 vs. 10.53%). The same trend was obtained with respect to chemical composition of by-products. Tilapia flesh raised in the first stocking rate had the lowest protein percentages (82.82%) and the largest fat percentage (9.98%), whereas the third stocking rate had the largest protein percentage (87.37%) and the lowest ash percentage (6.21%). The same trend of results was obtained with respect to chemical composition of by-products.
Silver carp flesh from fish raised under the first feeding treatment (M)compared with that fed the supplementary feed (F) had larger percentages of dry matter (22.14 vs. 20.98%), protein (84.39 vs. 77.65%), fat (9.52 vs. 6.48%), and lower percentages of ash (6.99 vs. 8.67%) and moisture (78.86 vs. 79.02%). Stocking rates of silver carp had insignificant effect on percentages of protein, fat and ash.
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