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This study aimed at assessing productive growth performance, blood physiology, intestinal histology, body composition and bone mineralization parameters of silver catfish juveniles fed diets containing different inclusion levels of sorghum, considering three combinations (0%, 50% or 100%), supplemented or not with phytase enzyme (0 and 1500 FTU kg −1 ). The apparent feed conversion and specific growth rate were benefited by supplemented diets (P < 0.05). The highest protein efficiency rate was obtained for the supplemented diet containing corn (P < 0.05). The viscerosomatic index was lower when corn/sorghum diet (P < 0.05) was offered, whilst the hepatosomatic index was lower in corn and corn/sorghum diets regardless of supplementation (P < 0.05). Regarding blood parameters, variations were observed (P < 0.05), however they were kept within the limits for the species. Histomorphometry variables also displayed variations, which were observed in fish fed with sorghum and sorghum/corn diets, supplemented or not (P < 0.05). Proximate composition of carcass varied for both aether extract and mineral matter for supplemented diets (P < 0.05). A variation of Ca content (P < 0.05) regarding bone mineralization was observed when corn and sorghum were used in the same proportion. Sorghum replacement of corn in diets for R. quelen may be a feasible alternative, and phytase supplementation with improves fish performance.

This study evaluated the use of wheat middling as a replacement for corn in diets supplemented or not with phytase, used to feed Rhamdia quelen silver catfish juveniles. A total of 288 juveniles were used and randomly distributed in 24 aquariums. Data were analyzed by factorial variance and, when significant, means were analyzed with the Tukey's test. Fish were fed four times daily until apparent satiety over the course of 45 days. The results of zootechnical performance showed that diet composition influenced the fat-somatic index with the 100% substitution level showing the lowest indexes. Fish fed with 100% wheat middling without phytase had the lowest chemical composition values of ethereal extracts in carcasses. Fish fed with phytase and 100% wheat middling had the lowest values of calcium and manganese in bone mineral composition. Intestinal histology analysis showed differences in villus height and villi total height in fish fed with the 67% replacement diet without phytase. The number of goblet cells was not statistically significant. It was concluded that wheat middling, supplemented or not with phytase, can effectively substitute corn in silver catfish diets without losses to productive performance, carcass chemical composition, bone mineral composition, and intestinal morphology.

Harina de girasol con y sin suplementación de fitasa en dietas para juveniles de bagre (barbudo, Col.;Rhamdia quelen) Farelo de girassol com e sem suplementação de fitase em dietas para juvenis de jundiá (Rhamdia quelen) meal with and without phytase supplementation in diets for silver catfish (Rhamdia quelen) juveniles. Rev Colomb Cienc Pecu 2019; 32(4): 285-297. AbstractBackground: The cost of feed in fish farming can exceed 70% of the total costs. Thus, the feed industry have sought to formulate balanced diets including low-cost by-products. Objective: To evaluate sunflower meal as a partial substitute (0, 10, and 20%) for soybean meal, with or without phytase supplementation (1,500 FTU/kg) in isoproteic (27% crude protein (CP)) and isoenergetic diets (3,400 kcal/ED/kg of feed) for silver catfish (Rhamdia quelen) juveniles. Methods: A total of 360 fish (weight: 15.77 ± 0.56 g) were randomly distributed in 24 tanks in a completely randomized design following a factorial scheme (3x2) with 4 replicates. The fish were evaluated on the following variables after 90 days: productive performance, hematological variables, histology of intestinal tissue, bromatological composition of carcass, and composition of bone mineral matter. Results: 20% dietary inclusion of sunflower meal improved weight gain and protein efficiency. No difference was observed in the other treatments and no interactions were observed between the other factors. Conclusion: 20% sunflower meal can be included in the feed of silver catfish as a substitute for soybean meal. Phytase inclusion (1,500 FTU/kg) did not improve the nutritional value of the treatments. ResumenAntecedentes: El costo de la alimentación en piscicultura pueden superar el 70% del costo total. Las industrias de alimentos para peces han intentado formular dietas balanceadas con subproductos de menor valor en el mercado para minimizar costos. Objetivo: Evaluar la harina de girasol como sucedáneo parcial (0, 10 y 20%) de la torta de soya, suplementada o no con fitasa (1.500 FTU/kg) en dietas isoprotéicas (27% de PB) e isoenergéticas 3400 kcal / ED / kg de ración) para bagre (barbudo, Col.; Rhamdia quelen). Métodos: Los peces, 360 juveniles (15,77 ± 0,56 g), se distribuyeron aleatoriamente en 24 unidades experimentales, en un diseño completamente al azar, en esquema factorial (3x2) y 4 repeticiones. A los 90 días se evaluó: desempeño productivo, variables hematológicas, histología de tejido intestinal y composición bromatológica de la carcasa y de la materia mineral de los huesos. Resultados: La inclusion de 20% de harina de girasol mejoró la ganancia de peso de los peces y la tasa de eficiencia proteica de la ración, sin diferencia para las otras evaluaciones ni interacción entre los demás factores evaluados. Conclusión: La harina de girasol se puede utilizar en un 20% de la ración del bagre (barbudo, Col.) como sucedáneo a la harina de soja. La inclusión de fitasa (1.500 FTU/kg) no mejoró el valor nutritivo de estas raciones. Palabras clave: acuacultura; acuicultura; bagre; barbudo;...