EFFECT OF DIFFERENT CRYOPROTECTANTS ON THE POST-THAW SPERM CHARACTERISTICS AND IN VIVO FERTILITY OF BUFFALO (Bubalus bubalus) BULL SEMEN

Abstract

This study aimed to investigate the effect of different cryoprotectants, glycerol (GLY) or ethylene glycol (EG) or dimethyl sulfoxide (DMSO) on sperm characteristics, and in vivo fertility of frozen-thawed buffalo-bull semen. A total of 85 ejaculates collected by artificial vagina from buffalo-bulls of proven fertility were used in this study. The collected ejaculates were examined for volume, motility, viability, morphology, and sperm cell concentration. The qualifying ejaculates (≥ 3 mass motion, > 70% progressive motility and viability, 1 x 109 sperm cells/mL) were pooled and diluted with Tris-based diluent containing either 7% GLY or 5% EG or 5% DMSO. After 4 h equilibration time, the diluted semen was loaded in 0.5 mL straws, labeled, sealed and frozen stored until analysis. Frozen straws were thawed and evaluated for progressive motility, viability, hypo-osmotic swelling test (HOST), acrosomal membrane integrity, and acrosome reaction (AR) in response to calcium ionophore A23187. Moreover, in vivo fertility was calculated after artificial insemination (AI) of 75 buffalo-cows (25 female/cryoprotectant) treated with double doses of prostaglandin F2α (PGF2α) 11 days interval. The proportions of progressive motility, viability and intact-acrosome were higher (p < 0.05) in extender containing 7% GLY compared to 5% EG and 5% DMSO. The proportion of intact-plasma membrane was comparable (p ≥ 0.05) between GLY and EG but higher than that of DMSO. A time-dependent increase in the % AR and % relative AR was recorded in the three cryoprotectants with clear significant (p < 0.01) difference among them at 30 and 60 min incubation, respectively. Moreover, GLY yielded higher pregnancy rate (52%) than EG (32%) and DMSO (16%). In conclusion, GLY is recommended for preservation of buffalo-bull semen in order to maintain sperm plasma membrane integrity and improve in vivo fertility of frozen-thawed buffalo-bull semen. Key words: buffalo-bull; frozen-thawed semen; cryoprotectant; estrus synchronization; In vivo fertility