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Thirty groups of twenty juveniles each of Nile tilapia (Oreochromis niloticus, initial average weight 23.93 ± 0.80 g) were fed diets containing increasing amounts (0%, 25%, 50%, 75%, and 100% of levels used by the tilapia feed industry) of organic trace mineral (Fe, Zn, Mn, Cu, Se) supplementation for 56 days. Growth was not affected by the dose of mineral supplementation. However, body protein increased in fish fed intermediate doses of organic minerals, reaching a maximum at 40.44% supplementation. Doses >50% showed mild damage to the intestinal tissue. Body Fe, Zn and Cu deposition were highest at 28.32%, 24.43% and 78.45% supplementation, respectively. Tilapia could modulate intestinal morphology when fed different doses of organic minerals. As the supplementation doses increased, hemosiderin staining increased in the distal intestine and total body Fe content, indicating that the distal region of the intestine plays an important role in iron excretion by tilapia. Supplementation of organic trace minerals at intermediate doses does not harm Nile tilapia growth, but excessive trace mineral supplementation can impair body protein retention and promote histological alterations in the gut.

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This study evaluated the effect of exogenous digestive enzymes on the survival, growth performance and morphology of the digestive tract of juveniles of the longsnout seahorse Hippocampus reidi fed exclusively with Artemia and supplemented with five different concentrations of porcine pancreatin (PP) (0, 5, 25, 50 and 75 mg/L from birth until 30 days after release). The results found in the present study clearly show that there was a significant increase in survival and growth as well as substantial changes in the morphology of intestinal villi in seahorses fed exclusively with Artemia supplemented with 75 mg/L PP. Therefore, the use of digestive enzyme supplementation constitutes an important advance for the establishment of a more efficient and practical feeding protocol (exclusive use of Artemia) for juveniles of the longsnout seahorse.