Seasonal influence on expression of heat shock proteins (HSP70 and HSP90) vis-à-vis functional competence of Gir bull semen

The success of assisted reproduction relies on functional competence of frozen-thawed semen. Heat stress affects protein folding leading to aggregation of mis-folded proteins. Hence, a total of 384 (32 ejaculates/bull/season) ejaculates from six matured Gir bulls were used to evaluate physico-morphological parameters, the expression of HSPs (70 and 90) and fertility of frozen-thawed semen. The mean percent individual motility, viability and membrane integrity were significantly (p < 0.01) higher in winter compared to summer. Out of 1200 Gir cows inseminated, 626 confirmed pregnant and the mean conception rate of winter (55.04 ± 0.35) was significantly (p < 0.001) higher than summer (49.33 ± 0.32). A significant (p < 0.01) difference in concentration of HSP70 (ng/mg of protein) but not HSP90was observed between the two seasons. The HSP70 expression in pre-freeze semen of Gir bulls had significant positive correlation with motility (p < 0.01, r = 0.463), viability (p < 0.01, r = 0.565), acrosome integrity (p < 0.05, r = 0.330) and conception rate (p < 0.01, r = 0.431). In conclusion, the season influences physico-morphological parameters and expression of HSP70 but not HSP90 in Gir bull semen. The HSP70 expression is positively correlated with motility, viability, acrosome integrity and fertility of semen. The semen expression of HSP70 may be utilized as biomarker for thermo-tolerance, semen quality and fertilizing capacity of Gir bull semen.

The effect of the freezing curve type on bull spermatozoa motility after thawing

The objective of this work was to determine the effect of selected freezing curves on spermatozoa survivability after thawing, defined by its motility. The ejaculates of nine selected sires of the same age, breed, and frequency of collecting, bred under the same breeding conditions including handling, stabling, feeding system and feeding ratio composition, were repeatedly collected and evaluated. Sperm samples of each sire were diluted using only one extender and divided into four parts. Selected four freezing curves – the standard, commercially recommended three-phase curve; a two-phase curve; a slow three-phase curve; and a fast three-phase curve, differing in the course of temperature vs time, were applied. The percentage rate of progressive motile spermatozoa above head was determined immediately after thawing, and after 30, 60, 90, and 120 min of the thermodynamic test (TDT). Moreover, average spermatozoa motility (AMOT) and spermatozoa motility decrease (MODE) throughout the entire TDT were evaluated. Insemination doses frozen using the simpler two-phase curve demonstrated the highest motility values (+2.97% to +10.37%; P < 0.05–0.01) immediately after thawing and during the entire TDT. Concurrently, the highest AMOT (+4.37% to +8.82%; P < 0.01) was determined. The highest spermatozoa motility values were detected after thawing doses frozen by the two-phase freezing curve in eight out of nine sires. Simultaneously, a significant effect of sire individuality was clearly confirmed. Inter-sire differences of spermatozoa motility during TDT as well as AMOT and MODE were significant (P < 0.01). The findings describing both factors of interaction indicate the necessity of individual cryopreservation of the ejaculate to increase its fertilization capability after thawing.