The influence of the length of time after hormonal treatment with [(d‐Ala6, Pro9 NEt)‐mGnRH+metoclopramide] i.e. Ovopel on barbel Barbus barbus (L.) milt quality and quantity indicators

The study purpose was the analysis of barbel Barbus barbus (L.) milt quality and quantity with regard to the time following stimulation with [(D‐Ala⁶, Pro⁹NEt)‐mGnRH+metoclopramide] i.e. Ovopel. Selected parameters such as total volume of milt (TVM, ml), volume of milt per kg of body weight (VOM, ml kg^?1 b.w.), sperm concentration (×10⁹ ml^?1), total sperm production (TSP, ×10⁹), osmolality (mOsm kg^?1) and pH of seminal plasma were determined. Sperm motility was analyzed by the CASA system, i.e. the percentage of sperm motility (MOT, %) and their progressive motility (PRG, %), curvilinear velocity (VCL, μm s^?1) and straight line velocity (VSL, μm s^?1), amplitude of lateral head displacement (ALH, μm), and beat cross frequency (BCF, Hz). Milt was collected from 12 specimens (N = 12), with the first portion obtained 12 h following treatment with Ovopel (1 granule kg^?1 b. w.). Subsequent portions of milt were taken at 24 h intervals, i.e. after 36, 60, 84, 108, and 132 h. The control group (Control, N = 12) was injected with 0.9% NaCl at 0.5 ml kg^?1b.w. from which milt was taken 12 h post injection. The highest TVM, VOM and TSP values were recorded 12 h after Ovopel treatment (3.2 ± 0.7 ml, 36.7 ± 10.5 ml kg^?1 b.w. and 39.1 ± 9.4 × 10⁹, respectively); lowest values were recorded after 132 h (0.8 ± 0.4 ml, 11.1 ± 6.5 ml kg^?1b.w. and 13.7 ± 7.5 × 10⁹, respectively). The highest seminal plasma osmolality values (300.0 ± 42.6 mOsm kg^?1) as well as the lowest sperm concentration (12.5 ± 1.5 × 10⁹ ml^?1) were observed 12 h after Ovopel treatment. No significant differences in the percentage of sperm motility (MOT) were noted during any of the periods after hormonal stimulation, however, a change in the character of their movement (PRG) was observed. The lack of significant differences (P > 0.05) in VCL and VSL values between 12 h and 60–132 h indicates that the lengthening of time does not lead to a decrease in sperm velocity and, therefore, is not likely to have a negative impact on their quality. The highest ALH (1.9 ± 0.2 μm) and BCF (11.5 ± 1.1 Hz) values were observed when the effect of stimulation was most noticeable, i.e. 12 h after Ovopel treatment. Based on the total milt volume and sperm production, the best time for milt collection from barbel is 12 h post‐hormonal treatment; 84 h post‐hormonal treatment, TVM, VOM, TSP and some CASA parameters decreased, which suggest the same aging process in sperm.