68 DIFFERENCE IN THAWING CURVE OF STALLION FROZEN SEMEN DILUTED IN 2 EXTENDERS

Abstract

Commercial freeze extenders have different composition and ratio of cryoprotectors; freezing and thawing protocols are different for each extender. The aim of this experiment was to observe the effect of thawing curve in stallion frozen semen with 2 commercial extenders. Two ejaculates from each of 9 stallions of different breeds (Quarter Horses and Mangalarga Marchador) were used. Semen was collected using an artificial vagina, and the ejaculate was divided into 2 groups following the manufacture's protocol: group 1 (INRA), in which the semen was diluted 1 : 1 with the extender INRA 96^TM (IMV, Paillette Crista, France) and group 2 (BC), in which the semen was diluted (1 : 1) with the extender Botu-Semen^TM (Botupharma, Brazil). The samples of the 2 groups were centrifuged at 600 × g for 10 min, the supernatant was discarded, and the pellet was resuspended with INRA Freeze^TM (group INRA, IMV) and with Botucrio^TM (group BC, Botupharma) at the concentration of sperm 100 × 10⁶ sperm mL^–1. After this, the semen was packaged in 0.5-mL straws. For each group the freezing process was carried out according to the manufacturer's instructions. The straws were thawed in a water bath with 3 different thawing curves: 37°C for 30 s (37/30), 46°C for 20 s (46/20), and 75°C for 7 s (75/7) before analysis. The aim of these rates is to keep the semen in 37°C post-thaw. The sperm kinetic analysis was performed by computerized method (CASA, HTM-IVOS, IMV, USA) and the analysis of plasma membrane integrity by flow cytometer (BD LSR Fortessa, Becton Dickinson, Mountain View, CA, USA). Data of sperm kinetic and of plasma membrane integrity were compared among the 3 thawing curves for one extender using analysis of variance. Differences were considered significant at a probability level of 5%. No differences were observed in total motility (%, BC 37/30 = 72.8 ± 14.4; BC 46/20 = 70.0 ± 14.2; BC 75/7 = 70.3 ± 12.0 v. INRA 37/30 = 57.2 ± 19.1; INRA 46/20 = 50.0 ± 21.9; BC 75/7 = 58.8 ± 20.8), progressive motility (%, BC 37/30 = 36.9 ± 8.2; BC 46/20 = 34.4 ± 10.5; BC 75/7 = 33.6 ± 7.8 v. INRA 37/30 = 25.3 ± 12.7; INRA 46/20 = 21.9 ± 13.9; BC 75/7 = 28.9 ± 14.8), rapid sperm (%, BC 37/30 = 59.7 ± 16.4; BC 46/20 = 56.8 ± 17.1; BC 75/7 = 58.1 ± 14.9 v. INRA 37/30 = 38.3 ± 20.9; INRA 46/20 = 35.3 ± 22.9; BC 75/7 = 44.4 ± 23.8), and plasma membrane integrity (%, BC 37/30 = 49.1 ± 14.8; BC 46/20 = 43.1 ± 13.1; BC 75/7 = 46.7 ± 11.8 v. INRA 37/30 = 32.2 ± 10.7; INRA 46/20 = 29.6 ± 10.1; BC 75/7 = 37.4 ± 9.1) among the 3 thawing curves for INRA and BC groups. In this study, we can conclude there is no influence of the 3 tested thawing curves in sperm quality for stallion frozen semen with INRA Freeze and Botucrio extenders.