Twenty-four ejaculates were collected from five boars for the conventional freezing procedure at the Veterinary School of Hannover (group 1A-1B) and for an extended holding time procedure (group 2A-2B and 3A-3B). The semen were prediluted in two different diluents, coconut water in natura and Merck I medium before freezing (experiment A) and prediluted only with Merck I, but cooling and freezing with coconut water in natura or lactose (experiment B). The semen were arranged into three groups according to the different holding periods before freezing, group 1A-1B (sperm-rich phase, preserved for 4 hours by 15°C), group 2A-2B (sperm-rich phase, preserved for 16 hours by 18°C) and group 3A-3B (total semen, preserved for 16 hours by 18ºC). The quality of the thawed boar spermatozoa was evaluated by subjective motility (SMOT), computerassisted motility (Cell Motion Analyser, Strömberg-Mica - CMOT) and morphology of acrosomal ridges (NAR) after fixation in formol citrate. The acrosomal integrity (NAR) was 65% (group 1A), 71% (group 2A) and 75% (group 3A) for semen prediluted with coconut water and 60% (group 1A), 68% (group 2A) and 68% (group 3A) for semen prediluted with Merck I medium, respectively (experiment A); and 56% (group 1B), 68% (group 2B) and 73% (group 3B) for semen freezing with coconut water diluent, and 60% group 1B), 68% (group 2B and 3B) for semen freezing with lactose (experiment B). Thus, did not differ significantly (p<0.05) between both pre-diluents and both freezing diluents. However, the post thaw motility by both SMOT and CMOT and the acrosome integrity (NAR) were significantly higher (p<0.05) in the semen preserved for extended holding time (group 2A-2B and 3A-3B) than those for short time (group 1A-1B). It is concluded that the extended holding time has a better effect to protect acrosome of boar spermatozoa and also maintain sperm motility. Therefore, preserving boar semen for longer period before freezing is indicated for subsequent research on in vitro research with boar semen. And because the results using coconut prediluent and diluent were similar to that using Merck I medium (experiment A) and using lactose (experiment B), it is also indicated to use coconut for diluent and for freezing boar semen.
Semen; Boar; Freezing; Diluents