Effects of Spirulina sp. on growth performance and antibody levels in hybrid catfish, Clarias macrocephalus x Clarias gariepinus (Burchell)

A 8-wk feeding trial was carried out for hybrid catfish with an initial average weight of 7 g in 235-l glass tanks attached to closed-recirculating system with 0.8 l/min flow rate. Feeds containing varying percentages of dry Spirulina sp. 0, 5, 10, 15, 20, 25 and 30% were tested with three replications for each treatment. All the feeds were formulated to contain dietary requirement for the catfish i.e. 30% protein, 7% fat and 360 kcal gross energy/ 100 g feed. The results showed that the feed with 10% Spirulina sp. achieved the best performance on weight gain, specific growth rate, feed conversion ratio, apparent net protein utilization and development of antibody levels against bacteria Aeromonas hydrophila. The total carotenoid contents in fish flesh increased with the level of Spirulina sp. supplemented. The supplementation of Spirulina sp. resulted in no changes of blood parameters or histology

Replacing palm kernel cake for fishmeal in sex-reversed red tilapia (Oreochromis niloticus Linn.) feed

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

Effects of mycotoxin T-2 and zearalenone on histopathological changes in black tiger shrimp (Penaeus monodon Fabricius)

The effects of T-2 toxin and zearalenone were studied in black tiger shrimp (Penaeus monodon Fabricius). In the experiment, black tiger shrimp were fed with different concentrations of T-2 toxin, i.e. 0, 0.1, 1.0 and 2.0 ppm and zearalenone, i.e. 0, 0.1. 0.5 and 1.0 ppm. Shrimp with initial average weight of 4.7 g were experimented for a-10-wk period. Supplementation of 0, 0.1 and 1.0 ppm T-2 produced no histological changes in hepatopancreatic, hemopoietic tissue or lymphoid cell while at higher concentration of 2.0 ppm atrophy, severe necrosis and degeneration of hepatopancreatic tubules, loose contact of hemopoietic tissue and lymphoid organ occurred. Similar observations were noted for the treatments with 0.5 and 1.0 ppm zearalenone - supplemented feed. Histological changes were, however, observed in hepatopancreatic tissue. The scale of histological changes correlated with feeding period and concentrations of zearalenone shrimp received