Biodiesel‐derived glycerol as a dietary maize replacement for silver catfish ( Rhamdia quelen ) during the fattening phase

Abstract

The aim of the present study was to assess the effects of crude biodiesel-derived glycerol on the zootechnical performance, carcass and fillet chemical composition, and blood parameters of silver catfish (Rhamdia quelen) during the fattening phase. A total of 150 adult silver catfish specimens (mean weight 188.89 ± 0.60 g) were distributed in thirty 1000 L-tanks containing a water recirculation system with mechanical filter and biofilter, in a completely randomized design comprising six treatments, 0%, 20%, 40%, 60%, 80% and 100% maize replacement by glycerol, with five repetitions each. The experiment was conducted for 206 days. Silver catfish morphometric parameters were not influenced (p > 0.05) by the glycerol maize replacement, although silver catfish standard length and width exhibited linear improvements (p < 0.05) with the dietary glycerol replacement. Fillet yield was affected (p < 0.05) by glycerol maize replacement, where the 80% replacement treatment led to better fillet yields (46.04%), differing only from the 20% replacement treatment (42.40% fillet yields). The blood plasma levels of glucose, pyruvic glutamic transaminase and triglycerides were influenced by the treatments (p < 0.05). The crude protein of fillet was influenced by the treatments (p < 0.05), where the highest value was observed in 100% glycerol maize replacement. Therefore, crude glycerol derived from biodiesel production is a suitable alternative energy source ingredient for silver catfish during their fattening phase, as it can replace maize in up to 100%.