Gonadorelin increases semen production and does not affect its quality in Leporinus obtusidens

- Gonadorelin is an effective inducer for Leporinus obtusidens males.
- Gonadorelin enhances semen production by increasing total expressible volume.
- Sperm quality was similar in gonadorelin-treated, untreated, and CPE-treated fish.
- The minimum effective gonadorelin dose for increasing semen volume is 60 μg kg−1.

Use of carp pituitary extract (CPE) as a hormone inducer for Leporinus obtusidens is cost-prohibitive; moreover, CPE contains unknown concentrations of gonadotropins. We evaluated the efficacy of gonadorelin as a substitute by analyzing its effect on sperm characteristics of L. obtusidens and cost-effectiveness (20, 40, 60, 80, and 100 μg kg−1). Untreated and CPE-treated (4 mg kg−1) fish were used as negative and positive controls, respectively. Following a single intramuscular dose of hormones, semen was collected at 200°-h. At doses from 60 μg kg−1, all fish produced higher milt volume (P < 0.05) than the negative control (0.2-0.8 mL kg−1), equal (P > 0.05) to the positive control (3.52 ± 0.97 mL kg−1). Gonadorelin did not affect sperm concentration (P > 0.05). The percentage of morphologically normal spermatozoa was >64% in all treatments. The number of spermatozoa with intact membrane (70%-85%) was equal (P > 0.05) to that in the controls. Relative to the negative control, gonadorelin did not affect the motility rate (P > 0.05). Curvilinear velocity was equal (P > 0.05) to that in both controls. The sperm swimming path was linear (0.9) 10 s after activation and was not (P > 0.05) dose-dependent. Considering the response rate of gonadorelin-induced fish and the similarity of semen quality compared to controls, the lowest effective dose to produce a higher volume of semen in L. obtusidens is 60 μg kg−1, and the cost to induce 1 kg of L. obtusidens is 14.0% lower than that with CPE.