Glycerol effects on silver catfish (Rhamdia quelen) fingerling feeding: Morphometric, zootechnical and blood parameters

Abstract

Decreasing natural fossil fuel stocks have supported the use of alternative fuels and increased the availability of glycerol, a biodiesel manufacture by-product. The use of glycerol in animal feed has been extensively investigated and reported as a potential energy source for different fish species. The aim of the present study was to evaluate the effect of crude glycerol as a corn substitute in the feeding of silver catfish fingerlings and on their zootechnical performance and blood parameters. One thousand and five hundred silver catfish fingerlings with an average weight of 1.5 ± 0.03 g were distributed in 301,000 L water tanks in a completely randomized design comprising six treatments (0, 20, 40, 60, 80 and 100% replacement of corn by glycerol) and five repetitions. The experimental period was of 75 days and the diet consisted of three daily meals until apparent satiety. Corn replacement by glycerol at up to 100% did not affect morphometric parameters, zootechnical performance, survival and calcium, cholesterol, alkaline phosphatase, total protein, oxalacetic and pyruvic glutamic transaminase and triglyceride blood parameters, although the plasma glucose rate of silver catfish fingerlings was significantly influenced (P < 0.05). It is concluded that the raw glycerol produced from biodiesel exhibits good potential for use as a corn substitute in silver catfish diets, and that the fingerlings of this species display the capacity to use up to 7.5% of glycerol inclusion or even total corn substitution without affecting morphometric and performance parameters or causing health damage.