Abstract
The transport of live fish is a routine practice in aquaculture and constitutes a considerable source of stress to the animals. The addition of anesthetic to the water used for fish transport can prevent or mitigate the deleterious effects of transport stress. This study investigated the effects of the addition of eugenol (EUG) (1.5 or 3.0 µL L-1) and essential oil of Lippia alba (EOL) (10 or 20 µL L-1) on metabolic parameters (glycogen, lactate and total protein levels) in liver and muscle, acetylcholinesterase activity (AChE) in muscle and brain, and the levels of protein carbonyl (PC), thiobarbituric acid reactive substances (TBARS) and nonprotein thiol groups (NPSH) and activity of glutathione-S-transferase in the liver of silver catfish (Rhamdia quelen; Quoy and Gaimard, 1824) transported for four hours in plastic bags (loading density of 169.2 g L-1). The addition of various concentrations of EUG (1.5 or 3.0 µL L-1) and EOL (10 or 20 µL L-1) to the transport water is advisable for the transportation of silver catfish, since both concentrations of these substances increased the levels of NPSH antioxidant and decreased the TBARS levels in the liver. In addition, the lower liver levels of glycogen and lactate in these groups and lower AChE activity in the brain (EOL 10 or 20 µL L-1) compared to the control group indicate that the energetic metabolism and neurotransmission were lower after administration of anesthetics, contributing to the maintenance of homeostasis and sedation status.
Highlights
During stressful situations, such as transport, fish demand greater amounts of energy, which can be obtained from glycogenolysis, gluconeogenesis and increases in protein turnover (Mommsen et al, 1999; Pankhurst, 2011)
Fish were divided into five treatment groups, each receiving one of the following treatments: control, 1.5 or 3.0 μL L–1 EUG (Odontofarma, Porto Alegre, Brazil), or 10 or 20 μL L–1 essential oil of Lippia alba (EOL)
Glycogen and lactate levels in the liver and muscle were significantly lower in all groups transported with EUG and EOL compared to the control group
Summary
During stressful situations, such as transport, fish demand greater amounts of energy, which can be obtained from glycogenolysis, gluconeogenesis and increases in protein turnover (Mommsen et al, 1999; Pankhurst, 2011). The use of anesthetics at sedative concentrations during fish transport could be an important tool to reduce sensitivity to stimuli, swimming time and stress (Ross and Ross, 2008; Zahl et al, 2010). Transportation in closed systems leads to changes in the metabolic state of fish and may lead to oxidative damage through the production of reactive oxygen species (ROS). The increase in ROS production often results in lipid peroxidation (which can be measured by thiobarbituric acid-reactive substances (TBARS) concentration), protein damage and decreased antioxidant protection. Oxidized proteins can form carbonyl groups (PC), which represent a marker of oxidative damage
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