Effect of different thawing methods on bull's semen characteristics

Abstract

The aim of the study was to evaluate the influence of different thawing methods on bull's semen characteristics. The semen was collected and processed from 8 bulls (Holstein, n = 4; Czech Fleckvieh, n = 4) kept in private Sire insemination Centre. Four different thawing methods were tested: control thawing methods (temperature = 38.5 $C, time = 30 seconds), slow thawing method (temperature = 30 $C, time = 50 seconds), moderate thawing method (temperature = 50 $C, time = 15 seconds), rapid thawing rate (temperature = 70 $C, time = 3 seconds). The percentage rate of total and progressive motile spermatozoa above head as well as movement characteristics of straight-line velocity (VSL, μm/s) and linearity (LIN, %) were recorded using CASA system immediately after thawing and after 2 hrs. of heat incubation (±38 $C). Subsequently the differences between semen characteristics measured immediately after thawing and after 2 hours of incubation were calculated. The data were analyzed with SAS software. All the evaluated semen traits reached significantly lowest values in total motility (-8 % to -10.5 %, P < 0.05), progressive motility (-5.6 % to -10 %, P < 0.05) VSL (-3.9 μm/s to -9 μm/s, P < 0.05) and LIN (-1.5 % to -4.8 %, P < 0.05) in control thawing method immediately after the thawing compared to others. However, these differences were negligible after 2 hrs. of incubation. The highest values of progressive motility and movement characteristics after thawing and after 2 hours incubation were detected using slow thawing method. Moreover, the rapid method of thawing showed the significantly the lowest results in progressive motility (-3.6 % to -6.6 %), VSL (-3.2 to -5.6 μm/s) and LIN (-3 % to -4.6 %) characteristics assessed after 2 hrs. of incubation compared the others (P < 0.05). Control method of thawing was most stable during the incubation and showed the significantly lowest decrease of total motility (-7.6 % to -11.8 %, P < 0.05), progressive spermatozoa motility above head (-7.5 % to -9.8 %, P < 0.05) and VSL characteristics (-2.4 to -9.7 μm/s, P < 0.05) during incubation. Therefore, this thawing protocol can be recommended at this study based on the lowest spermatozoa characteristics decline during incubation for using artificial insemination.