Characterization of the intravenous glucose tolerance test and the combined glucose-insulin test in donkeys.

This research focuses on describing two glucose-insulin test methods, the intravenous glucose tolerance test (IVGTT) and combined glucose-insulin test (CGIT), for the first time in adult donkeys. The aim is to understand glucose dynamics in donkeys, which vary from other species like horses, implying a need for animal-specific endocrine function assessment protocols.

Objective and Methodology

• The study primarily aimed to establish the characteristic features of IVGTT and CGIT tests in healthy adult donkeys. It also sought to define the normal glucose-insulin interaction parameters, known as proxies, for this species.
• A sample size of 16 donkeys was used, with their body morphometric variables collected for reference.
• IVGTT was performed by injecting glucose intravenously at 300 mg/kg dosage, while for the CGIT, an initial glucose dose (150 mg/kg) was followed by recombinant insulin (0.1 IU/kg).
• Blood samples were collected over 300 minutes post administration for glucose and insulin analysis.

Main Findings

• The IVGTT positive phase lasted 160.9 ± 13.3 minutes and peaked at a glucose concentration of 323.1 ± 9.2 mg/dL, declining at a rate of 1.28 ± 0.15 mg/dL/min. The areas under the curve (AUC) for glucose and insulin were 21.4 ± 1.9 × 10(3) mg/dL/min and 7.2 ± 0.9 × 10(3) µIU/mL/min respectively.
• The CGIT showed a positive phase of 44 ± 3 minutes with a glucose clearance rate of 2.01 ± 0.18 mg/dL/min. The negative phase lasted 255.9 ± 3 min, decreasing the glucose concentration at a rate of -0.63 ± 0.06 mg/dL/min, and reaching a lowest point (33.1 ± 3.6 mg/dL) at 118.3 ± 6.3 min. The AUC values for glucose and insulin were 15.2 ± 0.9 × 10(3) mg/dL/min and 13.2 ± 0.9 × 10(3) µIU/mL/min.

Implications of the Study

• This research presents the first characterization of glucose-insulin dynamics in donkeys using CGIT and IVGTT methodologies.
• The distinctive glucose dynamics in donkeys, as compared to horses, underline the need for species-specific protocols for endocrine function assessment, emphasizing the unique physiological requirements of different animal species.