The welfare impact of gavaging laboratory rats

Gavaging (oral dosing) has previously been shown to have only a short-term effect on behavioural parameters in the laboratory rat. The aim of this study was to determine if the gavaging of laboratory rats influenced their heart rate, blood pressure and body temperature, and if so, whether the duration of this impact correlated with the volume gavaged. The three stress parameters were measured using telemetric transponders placed in the abdomen of eight female Sprague-Dawley (Mol:SPRD) rats. Using a Latin Square cross-over design, the rats were gavaged with three different doses of barium sulphate (4, 10 and 40 ml kg⁻¹); in addition, there was a control of no dose, only insertion of the tube. The heart rate, blood pressure and body temperature of the rats were monitored continuously for 4 h after dosing and again for 1 h, 24 h after dosing. The gavaging of laboratory rats was shown to induce an acute reaction: after 30 min, blood pressure and heart rate were significantly higher than before gavaging, and body temperature was significantly higher 60 min after gavaging — indicators of stress levels comparable to those of other basic experimental procedures. A significant correlation between heart rate and dosage was observed until 10 min after gavaging. This indicates that the dosage gavaged is of only minor importance in causing stress, and only important for the most acute reaction. However, because of the resistance and discomfort observed when administering a 40 ml kg⁻¹ dose, this dose should be administered only with caution.