Effect of Medetomidine and Dexmedetomidine at Different Dosages on Cat Semen Quality Using Urethral Catheterization After Pharmacological Induction (UrCaPI)

The aim of this study was to evaluate the effectiveness of different anesthetic protocols for semen collection from healthy tomcats using Urethral Catheterization after Pharmacological Induction (UrCaPI). Twenty sexually mature tomcats (Felis catus) were included in the study, in which high and low dosages of medetomidine or dexmedetomidine were administrated to collect semen. Ten healthy mature tomcats (Group A) received high dosages of the drugs, and, in particular, five of them were i.m. injected with 120 μg/kg of medetomidine (HMED) on day 1 and with 60 μg/kg of dexmedetomidine (HDEX) after 24 h (day 2). The remaining five tomcats of this group were i.m. injected with 60 μg/kg of dexmedetomidine on day 1 and with 120 μg/kg of medetomidine on day 2. The other ten healthy mature tomcats (Group B) received a low dosage of the same drugs; the first five tomcats were i.m. injected with 50 μg/kg of medetomidine (LMED) on day 1 and with 25 μg/kg of dexmedetomidine (LDEX) on day 2; the others were i.m. injected with 25 μg/kg of dexmedetomidine on day 1 and with 50 μg/kg of medetomidine after 24 h. In both groups, semen collection was performed as soon as the pharmacological effect of the drug was reached. All protocols permitted sperm collection, even if with different results in quality for volume, concentration, total number of spermatozoa, and movement score. Results suggest that both a high dosage of medetomidine and a high dosage of dexmedetomidine could be used for the collection of good-quality semen. Semen volume μL: HMED = 32 μL (25.75-37.5), HDEX = 23 μL (15.25-28). Concentration HMED = 670 × 10⁶/mL (576-990.5), HDEX = 670.5 × 10⁶/mL (536-790). Total number of spermatozoa = 23.24 × 10⁶ (18.37-32.05). Total number of spermatozoa = 13.121 × 10⁶ (10.116-16.83). However, the protocol with dexmedetomidine could not always guarantee an adequate sedation for urethral catheterization, so using a high dosage of medetomidine is still the better way to collect high quality semen with the UrCaPI technique. The outcome of the LMED and LDEX protocols was generally unsatisfactory regarding both level of sedation and semen collection in terms of volume (LMED = 3 μL (4-7.5); LDEX = 6 μL (4-7)), concentration (LMED = 215 × 10⁶/mL (157-248); LDEX = 27.05 × 10⁶/mL (0.040-110), total number of spermatozoa (LMED = 0.88 × 10⁶ (0.581-1.38); LDEX = 0.16 × 10⁶ (0.0001-0.80), and movement score (LMED = 3 (2-3); LDEX = 2 (0-2.75)).