Maximal ventilation assessment in healthy calves.

Area of Science:

• Comparative physiology
• Respiratory physiology in livestock

Background:

• Accurate assessment of maximal ventilation is crucial for understanding respiratory function in cattle.
• Existing methods for inducing maximal ventilation, such as rebreathing trials, may have limitations in safety and standardization.

Purpose of the Study:

• To evaluate and compare the reliability of two methods for estimating maximal ventilation in calves: a rebreathing trial and lobeline administration.
• To determine the optimal lobeline dosage for inducing a maximal ventilatory response.

Main Methods:

• Twelve healthy calves were subjected to both a rebreathing trial and intravenous injections of increasing lobeline doses.
• Key ventilatory parameters, including tidal volume (VT), respiratory frequency (fR), and minute volume (VE), were recorded during maximal responses.
• The reproducibility and correlation between the two methods were assessed.

Main Results:

• The rebreathing trial induced a significant increase in VE (4.8 times resting value), primarily driven by increased VT.
• Lobeline administration dose-dependently increased ventilation up to 0.25 mg/kg, yielding a maximal response (3.7 times resting value) involving both fR and VT.
• The lobeline-induced maximal ventilation was reproducible and highly correlated (R=0.98) with the rebreathing trial response.

Conclusions:

• Both the rebreathing trial and lobeline administration are reliable methods for inducing and measuring maximal ventilation in calves.
• Lobeline administration (0.25 mg/kg) is a safe, standardized, and reproducible method, making it the preferred approach for studying maximal ventilation in calves.