# Effect of water temperature on the anesthetic effects of alfaxalone in carp (Cyprinus carpio)

## TL;DR

This study shows that lower water temperature increases the anesthetic effect of alfaxalone in carp when injected intramuscularly.

## Contribution

The novel finding is that water temperature significantly enhances alfaxalone's anesthetic effect in carp without changing heart or respiratory rates.

## Key findings

- Alfaxalone's anesthetic depth increased with dose but not with heart or respiratory rate changes.
- Lowering water temperature to 15°C made 2.5 mg/kg alfaxalone as effective as 5.0 mg/kg at 25°C.
- Intramuscular alfaxalone injection is a viable anesthetic method for carp.

## Abstract

To evaluate the effect of water temperature on intramuscular injected alfaxalone anesthesia in carp (Cyprinus carpio).

Six healthy adult carp (C. carpio) were intramuscularly injected with alfaxalone (2.5, 5.0, or 7.5 mg/kg) at normal water temperature (25°C) and at low water temperature (2.5 mg/kg, 15°C). The respiratory rate, heart rate (HR), and anesthesia depth (AD) were evaluated every 5 min for 30 min after administration and every 1 h after 60 min after injection.

The respiratory and HRs did not change significantly upon alfaxalone injection, regardless of dose. However, a dose-dependent increase in AD scores was observed. Furthermore, 2.5 mg/kg alfaxalone injected in 15°C water showed an almost equal anesthetic effect to that of 5.0 mg/kg alfaxalone in 25°C water.

Alfaxalone is readily available, and its anesthetic effect in carp was enhanced by lowering water temperature, illustrating the possibility of intramuscular injection of alfaxalone in fish.