Effect of bull on in vitro sperm capacitation induced by different agents in buffalo species (Bubalus bubalis)

The aim of this work was to evaluate the effect of bull on the efficacy of different capacitating agents in buffalo. Spermatozoa derived from 4 different bulls were incubated in absence of a capacitating agent, in presence of 0.01 mM heparin and in 20% buffalo estrous serum (BES) for 2 hours. Sperm were then exposed to lysophosphatidylcholine, an agent that induces acrosome reaction only on capacitated spermatozoa. A double staining technique with Trypan-blue/Giemsa was used to evaluate viability and acrosome status of spermatozoa fixed in 37% formaldehyde. The efficiency of capacitation was evaluated by assessing the percentage of acrosome-reacted (AR) spermatozoa in the treated groups. A bull effect on sperm capacitation in vitro was demonstrated, as indicated by differences in the percentage of AR sperm among bulls regardless of the treatment. In particular when heparin was used as capacitating agent bull C gave higher percentages of AR sperm than bull A (22.7 vs. 14.0%, respectively) with intermediate values for bulls B and D (16.7 and 19.1%, respectively), whereas when BES was used bull D was the most efficient one (22.1, 21.9, 25.0, and 35.0% for bulls A, B, C and D, respectively).