Evaluation of Glycerol from Biodiesel Production as a Feed Ingredient for Channel Catfish,Ictalurus punctatus

Abstract

Glycerol is the main by‐product of biodiesel production from vegetable oils and animal fats. It has been evaluated as an energy source for several farm animals. A study was conducted to examine the effects of various levels of glycerol in channel catfish, Ictalurus punctatus, diets. Fish with mean initial weight of 6.8 ± 0.1 g were stocked in 110‐L flow‐through aquaria and fed practical diets containing 0, 5, 10, 15, and 20% glycerol for 9 wk. There were no significant differences in feed consumption, weight gain, feed efficiency ratio, and liver lipid level among fish fed diets containing 0, 5, and 10% glycerol. However, fish fed diets containing 15 and 20% glycerol had reduced weight gain, feed efficiency, and liver lipid content. Survival was not affected by dietary glycerol levels. Blood glucose level was significantly higher in fish fed 5% glycerol than fish fed other diets. Fillet protein and fat generally decreased and fillet moisture increased as dietary glycerol level increased. It appears that channel catfish can utilize about 10% glycerol in the diet without adverse effects on feed consumption, weight gain, feed efficiency ratio, hemoglobin, hepatosomatic index, and liver lipid.

Growth and energy metabolism of Nile tilapia juveniles fed glycerol

“…In fish liver, malic enzyme is little affected by changes on the nature of dietary carbohydrates (Dias et al, 2004). In the present study, no significant differences were observed between treatments in the hepatic activity of the malic enzyme, considering that some authors consider glycerol as a carbohydrate source (Li et al, 2010). The obtained results suggest that fish fed 10 and 15% glycerol in their diet used glycerol as the lipogenic substratum in liver and muscle, given the higher activity of the G6PD hepatic enzyme and the higher amount of triglycerides found in these tissues.…”

“…The obtained results suggest that Nile tilapia juveniles have the ability to use glycerol as a substrate for tissue lipogenesis, indicating a greater fat deposition in the liver and muscle of fish, a not-desired feature due to the lack of consumer acceptance of fillet fat. However, Li et al (2010) found significantly lower liver lipid concentrations in channel catfish fed 15 and 20% glycerol than in those fed lower glycerol levels. This inconsistency may be related to the different feeding habits of the studied species.…”

“…In the present study, levels of glycerol in the diet did not affect plasma glucose concentrations. Li et al (2010) found higher levels of glucose in the blood of channel catfish fed diets containing 0 and 5% glycerol, which decreased in treatments containing 10, 15, and 20% glycerol used to substitute corn grain. This response cannot be easily explained, given that other carbohydrates, such as starch, and other nutrients also influence circulating glucose levels.…”

“…These results corroborate those of Neu et al (2013), who did not find any difference in the growth performance of Nile tilapia fed different levels of dietary glycerol. Li et al (2010) showed that the use of up to 10% dietary glycerol for channel catfish (Ictalurus punctatus) did not cause changes in weight gain, feeding efficiency, hepatosomatic index, and survival. However, the inclusion of 20% glycerol in the channel catfish diet negatively affected their growth performance.…”

Energia digestí­­vel e inclusão da glicerina bruta em dietas para juvenis de curimbatá

“…Estudos envolvendo a utilização do glicerol bruto na dieta de peixes iniciaram-se com o bagre-docanal, porém, sem levar em conta o valor digestível desse ingrediente (LI et al, 2010). Posteriormente foi relatado seu potencial uso como fonte energética para tilápia-do-nilo (MEURER et al, 2012), pacu e jundiá (BALEN et al, 2014).…”