RESUMO
Samples of semen from 12 pigs, three from Yorkshire, Landrace, Duroc and Mexican Hairless each where obtained to study cryopreservation methods. Three stages of boar semen cryopreservation were evaluated: none (fresh stage), cooling at 5 degrees C and freezing at -196 degrees C then thawing to 56 degrees C for 12 sec. Perinuclear theca damage and domain alterations were selected as indices of seminal quality, as measured by electronic and fluorescence microcopy, respectively according to two lineal models considering by separately the effect of semen preservation and breed. Integrity and absence of perinuclear theca significantly (p < 0.001) decreased and increased, respectively according to a decrease in temperature of cryopreservation, from 87.4 to 58.8% and from 0.8 to 26.2%, respectively. This same significant (p < 0.001) effect was found for acrosomal and post-acrosomal membrane distribution of domains, from 92.1 to 76.8% and from 3.1 to 13.1% in this same order. Slight but highly significant (p < 0.001) differences were observed when theca integrity was evaluated as affected by breed, with highest and lowest values for Yorkshire and Pel6n Mexicano pigs, respectively. No breed effect was encountered for presence of acrosomal domains. A strong interdependence was found between perinuclear theca damage and domain distribution. In this connection, a highly significant (p < 0.001) positive, interdependence was observed between the theca damage and acrosomal domain (r = 0.87), while this same relationship was although highly significant (p < 0.001), negative in nature for equatorial and post-acrosonal domains (r = -0.77 and -0.85, respectively). This experiment confirmed that cryopreservation methods may severely affect semen quality of pigs and that genotype may further influence these same indices. More research is needed for improving methods of preservation of pig semen quality, from the point of view of perinuclear theca and domain characteristics of spermatozoa.
