No abstract

Fish waste processed in the form of silage may constitute an alternative to the use of fishmeal (FM). In this study, the composition and quality of the acid silage produced from tuna viscera (TV) were characterized and the digestibility of the nutrients of this product was determined for jundia Rhamdia quelen, using ytrium oxide as an inert marker and a completely randomized design. At the end of thirty days, 61.74% of the crude protein of TV was solubilized. Acid silage from TV presented good nutritional composition (high protein, good amino acid profile and essential fatty acids) and good microbiological quality. Crude protein digestibility was similar (88.52%) for TV and FM, but dry matter digestibility was higher (P<0.05) for (TV) (92.20%). Tuna silage presented a high nutritional quality and nutrient digestibility for jundiá juveniles, R. quelen. Therefore, this novel ingredient has potential as an alternative protein source in aquafeeds.

Soy lecithin (SL) is a source of phospholipids, which play a crucial role in determining cell membrane structure, fluidity, and functionality. This study investigated the effects of dietary SL on the performance, nutrient digestibility, and body composition of Nile tilapia juveniles (average initial weight 12.2 g) raised at 22 °C. The experimental diets contained increasing levels of SL (0.0, 21.0, 43.0, and 64.0 g kg−1). The best weight gain and feed efficiency occurred with 42.2 and 49.8 g kg−1 of SL inclusion, respectively, estimated through quadratic regression after 90 days of feeding. The body composition of the fish was also affected by feeding with SL, with a decrease in total body lipids and viscerosomatic and hepatosomatic indices but an increase in polyunsaturated fatty acids. A digestibility trial using only two diets (0SLD and 43SLD) revealed increased lipid and fatty acids digestibility in fish fed with 43SLD. In addition, the consumption of digestible nutrients was the highest in fish fed the diet 43SL. Therefore, SL supplementation is beneficial in fall/spring diets for Nile tilapia juveniles as it can improve growth, lipid digestibility, and body composition when supplemented within the range of 42 to 50 g kg−1 diet.