Abstract
Abstract This study evaluated the addition of tung (Aleurites fordii) meal to the feed of Rhamdia quelen, as an alternative to animal protein sources. Silver catfish juveniles were fed different diets which included crude tung meal, chemically treated tung meal and a control without tung meal. The chemical treatment was based on the sequential application of acid and alcohol solutions and reduced the phytic acid from 1.63 to 0.61% and condensed tannin content from 0.025 to 0.018%. The nutritional response of fish to these ingredients was evaluated over nine weeks, based on growth performance, digestive enzyme activity and biochemical responses. After nine weeks, the diet containing crude tung meal caused reduced growth (weight: -57.9%; total length: -21.09%; specific growth rate: -99.74%). This diet also reduced acid protease and lipase activities, decreased concentrations of glucose, cholesterol and triglycerides in plasma and decreased liver glycogen and glucose concentrations. However, after nine weeks, fish fed with treated tung meal showed higher growth (weight, total length and specific growth rate similar to control) and reduced metabolic changes, possibly due to the removal of antinutrients and toxic substances. At the 32% level of inclusion, the chemically treated tung meal can be considered an alternative protein source for silver catfish.
Highlights
Among the most prominent oilseeds used for biofuel production in Brazil are soybean, sunflower, palm, castor and canola
The inclusion of crude tung meal in silver catfish feed resulted in a significant reduction in growth after three, six and nine weeks
Lower live weight (LW), total length (TL) and specific growth rates (SGR) were observed in these animals compared with those fed with diets containing treated tung meal and the control diet (Table 4)
Summary
Among the most prominent oilseeds used for biofuel production in Brazil are soybean, sunflower, palm, castor and canola. A promising new agricultural product is tung (Aleurites fordii), a perennial plant native to China whose fruits contain a high oil content (47–63%). The average fruit yield reaches 9,000 kg/ha, and the extracted oil is currently used in the production of paints and resins but could potentially be used as an alternative oil in the biodiesel industry[2]. The production of biofuels, like all industrial activity, generates large amounts shells, meals and pies (obtained from the mechanical pressing of oil seeds). A carefully studied and excellent alternative use for these by-products is in fish farming, since the commercial aquafeed companies are seeking alternative ingredients (considering both economic and environmental aspects) to replace the animal protein sources (fish and meat meals) that are traditionally used, as these have high costs and high heterogeneity in their nutritional composition[3]
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