Thermal dynamics and physiological implications in pacu Piaractus mesopotamicus anaesthetised with Ocimum basilicum essential oil

Document Type : Original Article

Authors

1 Faculty of Veterinary Medicine and Animal Science – FAMEZ, Federal University of Mato Grosso do Sul, Av. Sen. Filinto Müller, 2443 Campo Grande - MS, 79070-900, Brazil

2 Faculty of Agricultural Sciences – FCA, Federal University of Grande Dourados, Rodovia Dourados/Itahum, Km 12 - Unidade II Caixa Postal: 364, Dourados - MS, 79804-970, Brazil

3 Institute of Studies in Agrarian and Regional Development, Faculty of Agronomy of Marabá, Federal University of the South and Southeast of Pará, Marabá, PA, Brazil

4 Federal University of Amazonas - UFAM, Av. Rodrigo Otávio, 6200, Manaus - AM, CEP 69080-900, Brazil

Abstract

The aim of this study was to evaluate the haematological, biochemical and body temperature parameters of pacu Piaractus mesopotamicus juveniles after capture stress followed by anaesthetic induction. Fish (30.4±1.4 g) were divided into five groups (12 fish each group): control (water only handling), ethanol handling (600 µL L-1), handling with 100, 350 and 600 mg L-1 of essential Ocimum basilicum oil. Fish were caught and anaesthetised, followed by biometric handling, blood collection and thermographic images. Increased anaesthetic concentrations had a linear positive effect on haemoglobin content, erythrocytes, mean corpuscular haemoglobin concentration (MCHC), monocytes and granular leukocyte PAS positive (LG-PAS) (P<0.05). A quadratic effect (P<0.05) was observed for lymphocytes, with a maximum peak at the 350 mg L-1 concentration. The fish surface temperature ranged was 25.9-29.9 ºC, with the highest values in the non-anaesthetised fish’s cephalic regions. The fish anaesthetised with the O. basilicum essential oil 100 mg L-1 concentration showed a lower surface temperature. Using O. basilicum essential oil in biometric handling procedures was unable to prevent stress-related haematological alterations in juvenile pacu. Employing infrared thermography to assess surface temperature provides useful data to understand the effects of anaesthesia on fish, but more studies are needed to better understand this technique as a measure of well-being in fish farming.

Keywords