Natural anesthetics in the transport of Nile tilapia: Hematological and biochemical responses and residual concentration in the fillet

Abstract

This study assessed the hematological and biochemical effects of natural anesthetics used in the transport of Nile tilapia (Oreochromis niloticus) and their residual concentration in the fish fillet. One hundred fish with an average weight of 816.36 ± 31.37 g and an average standard length of 31.27 ± 1.42 cm were distributed among five treatments: non-transported fish; fish transported in water only (control), fish transported in water + anesthetic vehicle (ethanol 36 μL L−1), fish transported in water + eugenol (20 μL L−1), and fish transported in water + Ocimum basilicum essential oil (20 μL L−1). The fish were transported in boxes (1.45 m long × 1.08 m wide × 1.03 m high, Trevisan®) for 2 h. Subsequently, hematological and biochemical parameters were evaluated. Meanwhile, fillet samples were removed to determine the level of residual deposition of those compounds in the fish muscle by gas chromatography–mass spectrometry (GC–MS). The fish transported with natural anesthetics showed a lower (p < .05) number of erythrocytes. Sedation with O. basilicum prevented alterations in energy metabolism, but did not prevent changes in the chloride and sodium electrolytes (p < .05). Glucose was higher (p < .05) in the fish from the eugenol group. The major components of O. basilicum essential oil were methyl chavicol (66.51%) and linalool (20.90%). The residual levels of the methyl chavicol and eugenol compounds in Nile tilapia fillets were 20.52 ± 2.05 and 75.04 ± 3.76 μg kg−1, respectively, which are below the acceptable levels of O. basilicum essential oil and eugenol for human consumption. Therefore, the natural anesthetics exhibited sedative capacity and did not cause harm, but induced alterations typical of physiological adjustments during transport stress.