Effect of time after hormonal stimulation on semen quality indicators of common carp, Cyprinus carpio (Actinopterygii: Cypriniformes: Cyprinidae)

Abstract

Background. Obtaining the appropriate quantity of milt and spermatozoa of biologically good quality depends on a number of environmental factors. Additional factors may be involved while using a hormonal stimulation. The aim of this study was to analyse the effect of time, after stimulation with Ovopel [(D-Ala6, Pro9-NEt)-mGnRH+metoclopramide] (1 granule · kg–1 body weight) on semen quality indicators of common carp, Cyprinus carpio L., over the period of 72 h post injection. Materials and methods. The total volume of milt (TVM, mL), volume of milt per 1 kg of the male body weight (VOM, mL ·  kg–1 b.w.), total sperm production (TSP, ×109), and their concentration (×109 mL–1) in milt were determined. Additionally, the motility of spermatozoa (%) by means of the subjective method and the osmotic pressure of seminal plasma (mOsm · · kg–1) were determined. The milt was collected 24 h (group I, n = 10), 48 h (group II, n = 10), and 72 h (group III, n = 10) after stimulation with Ovopel. Results. No significant differences (P > 0.05) in the main parameters of milt i.e., the motility and concentration of spermatozoa in the milt, as well as in the osmotic pressure of seminal plasma were found between the experimental groups of the fish. Higher TSP and VOM values were recorded 24 h after Ovopel injection compared to samples obtained after 72 h (P <0.01 and P < 0.05, respectively) and 48 h (P > 0.05). TVM values were also higher at 24 h after the injection than those noted at 48 and 72 h (P < 0.01). Conclusion. The lack of significant differences in the motility and concentration of spermatozoa in milt at 24, 48, and 72 h after injection indicate that time after Ovopel administration does not have an influence on the main indicators of common carp milt quality. However, we noted significant differences in TSP, TVM, and VOM between samples obtaining 24 h and 72 h after hormonal stimulation. The highest quantity indicators i.e., the number of spermatozoa in milt and volume of obtained milt noted for samples obtained after 24 h suggest that this time is better for milt sampling than time after 48 and 72 h.

Keywords

• Cyprinus carpio
• milt
• spermatozoa
• seminal plasma