Comparison of two pharmacological semen collection times with α2-adrenergic agonist in domestic cats

The use of α2-adrenergic agonists in association with urethral catheterization has been used as a technique for pharmacological semen collection in cats. The mechanism of action of this drug is the stimulation of adrenoreceptors in the vas deferens, which results in ejaculation. While medetomidine is the α2-agonist most commonly used in studies, ejaculation with the use of dexmedetomidine associated with ketamine has been effective, but with variable results. Therefore, further studies regarding the methodology of use are required to obtain better seminal quality. This study aimed to compare two pharmacological semen collection times after the association of dexmedetomidine (30 μg/kg, IM; Dormitor®, Zoetis), ketamine (5 mg/kg, IM; ketamine, Vetnil) and urethral catheterization using a tomcat probe (0.8 mm × 1.00 mm × 11 cm). The collections were divided into two experimental groups: G10 (N = 8; urethral catheterization after 10 min of anaesthesia) and G15 (N = 8; urethral catheterization after 15 min of anaesthesia). The ejaculates were evaluated for ejaculate volume, sperm concentration, morphology and kinetics using the CASA system. To compare the groups, the t-test and the Mann-Whitney U-test were used with a significance level of 5%. It was identified that ejaculate volume (G10: 22.62 ± 2.13 vs. G15: 26.81 ± 1.55; p < .001) and sperm concentration (G10: 48.10 × 10⁶  ± 17.84 vs. G15: 90.18 × 10⁶  ± 19.35; p < .001) was higher in G15 than in G10 and had a lower percentage of minor defects than G10 (G10: 3.12 ± 2.41 vs. G15: 1.00 ± 1.19; p = .043). Regarding the kinetic parameters, the results of G15 were better for total motility-TM (G10: 67.00 ± 10.33 vs. G15: 81.87 ± 7.99; p = .006) and faster cells-RAPID: (G10: 55.00 ± 16.63 vs. G15: 74.25 ± 11.94; p = .019); whereas a higher proportion of cells with slow speed-SLOW were seen in G10 (G10: 31.00 ± 12.07 vs. 17.12 ± 7.53; p = .015). Based on these findings, we suggest that collection via urethral catheterization should be performed 15 min after the application of ketamine-associated dexmedetomidine to obtain a better-quality ejaculate.